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linux/mm/mmap.c
Lorenzo Stoakes 54cbbbf3fa mm/mmap: separate writenotify and dirty tracking logic 
Patch series "mm/gup: disallow GUP writing to file-backed mappings by
default", v9.

Writing to file-backed mappings which require folio dirty tracking using
GUP is a fundamentally broken operation, as kernel write access to GUP
mappings do not adhere to the semantics expected by a file system.

A GUP caller uses the direct mapping to access the folio, which does not
cause write notify to trigger, nor does it enforce that the caller marks
the folio dirty.

The problem arises when, after an initial write to the folio, writeback
results in the folio being cleaned and then the caller, via the GUP
interface, writes to the folio again.

As a result of the use of this secondary, direct, mapping to the folio no
write notify will occur, and if the caller does mark the folio dirty, this
will be done so unexpectedly.

For example, consider the following scenario:-

1. A folio is written to via GUP which write-faults the memory, notifying
   the file system and dirtying the folio.
2. Later, writeback is triggered, resulting in the folio being cleaned and
   the PTE being marked read-only.
3. The GUP caller writes to the folio, as it is mapped read/write via the
   direct mapping.
4. The GUP caller, now done with the page, unpins it and sets it dirty
   (though it does not have to).

This change updates both the PUP FOLL_LONGTERM slow and fast APIs.  As
pin_user_pages_fast_only() does not exist, we can rely on a slightly
imperfect whitelisting in the PUP-fast case and fall back to the slow case
should this fail.


This patch (of 3):

vma_wants_writenotify() is specifically intended for setting PTE page
table flags, accounting for existing page table flag state and whether the
underlying filesystem performs dirty tracking for a file-backed mapping.

Everything is predicated firstly on whether the mapping is shared
writable, as this is the only instance where dirty tracking is pertinent -
MAP_PRIVATE mappings will always be CoW'd and unshared, and read-only
file-backed shared mappings cannot be written to, even with FOLL_FORCE.

All other checks are in line with existing logic, though now separated
into checks eplicitily for dirty tracking and those for determining how to
set page table flags.

We make this change so we can perform checks in the GUP logic to determine
which mappings might be problematic when written to.

Link: https://lkml.kernel.org/r/cover.1683235180.git.lstoakes@gmail.com
Link: https://lkml.kernel.org/r/0f218370bd49b4e6bbfbb499f7c7b92c26ba1ceb.1683235180.git.lstoakes@gmail.com
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Mika Penttilä <mpenttil@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Kirill A . Shutemov <kirill@shutemov.name>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-06-09 16:25:56 -07:00

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// SPDX-License-Identifier: GPL-2.0-only
/*
* mm/mmap.c
*
* Written by obz.
*
* Address space accounting code <alan@lxorguk.ukuu.org.uk>
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/backing-dev.h>
#include <linux/mm.h>
#include <linux/mm_inline.h>
#include <linux/shm.h>
#include <linux/mman.h>
#include <linux/pagemap.h>
#include <linux/swap.h>
#include <linux/syscalls.h>
#include <linux/capability.h>
#include <linux/init.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/personality.h>
#include <linux/security.h>
#include <linux/hugetlb.h>
#include <linux/shmem_fs.h>
#include <linux/profile.h>
#include <linux/export.h>
#include <linux/mount.h>
#include <linux/mempolicy.h>
#include <linux/rmap.h>
#include <linux/mmu_notifier.h>
#include <linux/mmdebug.h>
#include <linux/perf_event.h>
#include <linux/audit.h>
#include <linux/khugepaged.h>
#include <linux/uprobes.h>
#include <linux/notifier.h>
#include <linux/memory.h>
#include <linux/printk.h>
#include <linux/userfaultfd_k.h>
#include <linux/moduleparam.h>
#include <linux/pkeys.h>
#include <linux/oom.h>
#include <linux/sched/mm.h>
#include <linux/ksm.h>
#include <linux/uaccess.h>
#include <asm/cacheflush.h>
#include <asm/tlb.h>
#include <asm/mmu_context.h>
#define CREATE_TRACE_POINTS
#include <trace/events/mmap.h>
#include "internal.h"
#ifndef arch_mmap_check
#define arch_mmap_check(addr, len, flags) (0)
#endif
#ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS
const int mmap_rnd_bits_min = CONFIG_ARCH_MMAP_RND_BITS_MIN;
const int mmap_rnd_bits_max = CONFIG_ARCH_MMAP_RND_BITS_MAX;
int mmap_rnd_bits __read_mostly = CONFIG_ARCH_MMAP_RND_BITS;
#endif
#ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
const int mmap_rnd_compat_bits_min = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MIN;
const int mmap_rnd_compat_bits_max = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MAX;
int mmap_rnd_compat_bits __read_mostly = CONFIG_ARCH_MMAP_RND_COMPAT_BITS;
#endif
static bool ignore_rlimit_data;
core_param(ignore_rlimit_data, ignore_rlimit_data, bool, 0644);
static void unmap_region(struct mm_struct *mm, struct maple_tree *mt,
struct vm_area_struct *vma, struct vm_area_struct *prev,
struct vm_area_struct *next, unsigned long start,
unsigned long end, bool mm_wr_locked);
static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags)
{
return pgprot_modify(oldprot, vm_get_page_prot(vm_flags));
}
/* Update vma->vm_page_prot to reflect vma->vm_flags. */
void vma_set_page_prot(struct vm_area_struct *vma)
{
unsigned long vm_flags = vma->vm_flags;
pgprot_t vm_page_prot;
vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, vm_flags);
if (vma_wants_writenotify(vma, vm_page_prot)) {
vm_flags &= ~VM_SHARED;
vm_page_prot = vm_pgprot_modify(vm_page_prot, vm_flags);
}
/* remove_protection_ptes reads vma->vm_page_prot without mmap_lock */
WRITE_ONCE(vma->vm_page_prot, vm_page_prot);
}
/*
* Requires inode->i_mapping->i_mmap_rwsem
*/
static void __remove_shared_vm_struct(struct vm_area_struct *vma,
struct file *file, struct address_space *mapping)
{
if (vma->vm_flags & VM_SHARED)
mapping_unmap_writable(mapping);
flush_dcache_mmap_lock(mapping);
vma_interval_tree_remove(vma, &mapping->i_mmap);
flush_dcache_mmap_unlock(mapping);
}
/*
* Unlink a file-based vm structure from its interval tree, to hide
* vma from rmap and vmtruncate before freeing its page tables.
*/
void unlink_file_vma(struct vm_area_struct *vma)
{
struct file *file = vma->vm_file;
if (file) {
struct address_space *mapping = file->f_mapping;
i_mmap_lock_write(mapping);
__remove_shared_vm_struct(vma, file, mapping);
i_mmap_unlock_write(mapping);
}
}
/*
* Close a vm structure and free it.
*/
static void remove_vma(struct vm_area_struct *vma, bool unreachable)
{
might_sleep();
if (vma->vm_ops && vma->vm_ops->close)
vma->vm_ops->close(vma);
if (vma->vm_file)
fput(vma->vm_file);
mpol_put(vma_policy(vma));
if (unreachable)
__vm_area_free(vma);
else
vm_area_free(vma);
}
static inline struct vm_area_struct *vma_prev_limit(struct vma_iterator *vmi,
unsigned long min)
{
return mas_prev(&vmi->mas, min);
}
static inline int vma_iter_clear_gfp(struct vma_iterator *vmi,
unsigned long start, unsigned long end, gfp_t gfp)
{
vmi->mas.index = start;
vmi->mas.last = end - 1;
mas_store_gfp(&vmi->mas, NULL, gfp);
if (unlikely(mas_is_err(&vmi->mas)))
return -ENOMEM;
return 0;
}
/*
* check_brk_limits() - Use platform specific check of range & verify mlock
* limits.
* @addr: The address to check
* @len: The size of increase.
*
* Return: 0 on success.
*/
static int check_brk_limits(unsigned long addr, unsigned long len)
{
unsigned long mapped_addr;
mapped_addr = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
if (IS_ERR_VALUE(mapped_addr))
return mapped_addr;
return mlock_future_ok(current->mm, current->mm->def_flags, len)
? 0 : -EAGAIN;
}
static int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *brkvma,
unsigned long addr, unsigned long request, unsigned long flags);
SYSCALL_DEFINE1(brk, unsigned long, brk)
{
unsigned long newbrk, oldbrk, origbrk;
struct mm_struct *mm = current->mm;
struct vm_area_struct *brkvma, *next = NULL;
unsigned long min_brk;
bool populate;
bool downgraded = false;
LIST_HEAD(uf);
struct vma_iterator vmi;
if (mmap_write_lock_killable(mm))
return -EINTR;
origbrk = mm->brk;
#ifdef CONFIG_COMPAT_BRK
/*
* CONFIG_COMPAT_BRK can still be overridden by setting
* randomize_va_space to 2, which will still cause mm->start_brk
* to be arbitrarily shifted
*/
if (current->brk_randomized)
min_brk = mm->start_brk;
else
min_brk = mm->end_data;
#else
min_brk = mm->start_brk;
#endif
if (brk < min_brk)
goto out;
/*
* Check against rlimit here. If this check is done later after the test
* of oldbrk with newbrk then it can escape the test and let the data
* segment grow beyond its set limit the in case where the limit is
* not page aligned -Ram Gupta
*/
if (check_data_rlimit(rlimit(RLIMIT_DATA), brk, mm->start_brk,
mm->end_data, mm->start_data))
goto out;
newbrk = PAGE_ALIGN(brk);
oldbrk = PAGE_ALIGN(mm->brk);
if (oldbrk == newbrk) {
mm->brk = brk;
goto success;
}
/*
* Always allow shrinking brk.
* do_vma_munmap() may downgrade mmap_lock to read.
*/
if (brk <= mm->brk) {
int ret;
/* Search one past newbrk */
vma_iter_init(&vmi, mm, newbrk);
brkvma = vma_find(&vmi, oldbrk);
if (!brkvma || brkvma->vm_start >= oldbrk)
goto out; /* mapping intersects with an existing non-brk vma. */
/*
* mm->brk must be protected by write mmap_lock.
* do_vma_munmap() may downgrade the lock, so update it
* before calling do_vma_munmap().
*/
mm->brk = brk;
ret = do_vma_munmap(&vmi, brkvma, newbrk, oldbrk, &uf, true);
if (ret == 1) {
downgraded = true;
goto success;
} else if (!ret)
goto success;
mm->brk = origbrk;
goto out;
}
if (check_brk_limits(oldbrk, newbrk - oldbrk))
goto out;
/*
* Only check if the next VMA is within the stack_guard_gap of the
* expansion area
*/
vma_iter_init(&vmi, mm, oldbrk);
next = vma_find(&vmi, newbrk + PAGE_SIZE + stack_guard_gap);
if (next && newbrk + PAGE_SIZE > vm_start_gap(next))
goto out;
brkvma = vma_prev_limit(&vmi, mm->start_brk);
/* Ok, looks good - let it rip. */
if (do_brk_flags(&vmi, brkvma, oldbrk, newbrk - oldbrk, 0) < 0)
goto out;
mm->brk = brk;
success:
populate = newbrk > oldbrk && (mm->def_flags & VM_LOCKED) != 0;
if (downgraded)
mmap_read_unlock(mm);
else
mmap_write_unlock(mm);
userfaultfd_unmap_complete(mm, &uf);
if (populate)
mm_populate(oldbrk, newbrk - oldbrk);
return brk;
out:
mmap_write_unlock(mm);
return origbrk;
}
#if defined(CONFIG_DEBUG_VM_MAPLE_TREE)
static void validate_mm(struct mm_struct *mm)
{
int bug = 0;
int i = 0;
struct vm_area_struct *vma;
VMA_ITERATOR(vmi, mm, 0);
mt_validate(&mm->mm_mt);
for_each_vma(vmi, vma) {
#ifdef CONFIG_DEBUG_VM_RB
struct anon_vma *anon_vma = vma->anon_vma;
struct anon_vma_chain *avc;
#endif
unsigned long vmi_start, vmi_end;
bool warn = 0;
vmi_start = vma_iter_addr(&vmi);
vmi_end = vma_iter_end(&vmi);
if (VM_WARN_ON_ONCE_MM(vma->vm_end != vmi_end, mm))
warn = 1;
if (VM_WARN_ON_ONCE_MM(vma->vm_start != vmi_start, mm))
warn = 1;
if (warn) {
pr_emerg("issue in %s\n", current->comm);
dump_stack();
dump_vma(vma);
pr_emerg("tree range: %px start %lx end %lx\n", vma,
vmi_start, vmi_end - 1);
vma_iter_dump_tree(&vmi);
}
#ifdef CONFIG_DEBUG_VM_RB
if (anon_vma) {
anon_vma_lock_read(anon_vma);
list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
anon_vma_interval_tree_verify(avc);
anon_vma_unlock_read(anon_vma);
}
#endif
i++;
}
if (i != mm->map_count) {
pr_emerg("map_count %d vma iterator %d\n", mm->map_count, i);
bug = 1;
}
VM_BUG_ON_MM(bug, mm);
}
#else /* !CONFIG_DEBUG_VM_MAPLE_TREE */
#define validate_mm(mm) do { } while (0)
#endif /* CONFIG_DEBUG_VM_MAPLE_TREE */
/*
* vma has some anon_vma assigned, and is already inserted on that
* anon_vma's interval trees.
*
* Before updating the vma's vm_start / vm_end / vm_pgoff fields, the
* vma must be removed from the anon_vma's interval trees using
* anon_vma_interval_tree_pre_update_vma().
*
* After the update, the vma will be reinserted using
* anon_vma_interval_tree_post_update_vma().
*
* The entire update must be protected by exclusive mmap_lock and by
* the root anon_vma's mutex.
*/
static inline void
anon_vma_interval_tree_pre_update_vma(struct vm_area_struct *vma)
{
struct anon_vma_chain *avc;
list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
anon_vma_interval_tree_remove(avc, &avc->anon_vma->rb_root);
}
static inline void
anon_vma_interval_tree_post_update_vma(struct vm_area_struct *vma)
{
struct anon_vma_chain *avc;
list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
anon_vma_interval_tree_insert(avc, &avc->anon_vma->rb_root);
}
static unsigned long count_vma_pages_range(struct mm_struct *mm,
unsigned long addr, unsigned long end)
{
VMA_ITERATOR(vmi, mm, addr);
struct vm_area_struct *vma;
unsigned long nr_pages = 0;
for_each_vma_range(vmi, vma, end) {
unsigned long vm_start = max(addr, vma->vm_start);
unsigned long vm_end = min(end, vma->vm_end);
nr_pages += PHYS_PFN(vm_end - vm_start);
}
return nr_pages;
}
static void __vma_link_file(struct vm_area_struct *vma,
struct address_space *mapping)
{
if (vma->vm_flags & VM_SHARED)
mapping_allow_writable(mapping);
flush_dcache_mmap_lock(mapping);
vma_interval_tree_insert(vma, &mapping->i_mmap);
flush_dcache_mmap_unlock(mapping);
}
static int vma_link(struct mm_struct *mm, struct vm_area_struct *vma)
{
VMA_ITERATOR(vmi, mm, 0);
struct address_space *mapping = NULL;
if (vma_iter_prealloc(&vmi))
return -ENOMEM;
if (vma->vm_file) {
mapping = vma->vm_file->f_mapping;
i_mmap_lock_write(mapping);
}
vma_iter_store(&vmi, vma);
if (mapping) {
__vma_link_file(vma, mapping);
i_mmap_unlock_write(mapping);
}
mm->map_count++;
validate_mm(mm);
return 0;
}
/*
* init_multi_vma_prep() - Initializer for struct vma_prepare
* @vp: The vma_prepare struct
* @vma: The vma that will be altered once locked
* @next: The next vma if it is to be adjusted
* @remove: The first vma to be removed
* @remove2: The second vma to be removed
*/
static inline void init_multi_vma_prep(struct vma_prepare *vp,
struct vm_area_struct *vma, struct vm_area_struct *next,
struct vm_area_struct *remove, struct vm_area_struct *remove2)
{
memset(vp, 0, sizeof(struct vma_prepare));
vp->vma = vma;
vp->anon_vma = vma->anon_vma;
vp->remove = remove;
vp->remove2 = remove2;
vp->adj_next = next;
if (!vp->anon_vma && next)
vp->anon_vma = next->anon_vma;
vp->file = vma->vm_file;
if (vp->file)
vp->mapping = vma->vm_file->f_mapping;
}
/*
* init_vma_prep() - Initializer wrapper for vma_prepare struct
* @vp: The vma_prepare struct
* @vma: The vma that will be altered once locked
*/
static inline void init_vma_prep(struct vma_prepare *vp,
struct vm_area_struct *vma)
{
init_multi_vma_prep(vp, vma, NULL, NULL, NULL);
}
/*
* vma_prepare() - Helper function for handling locking VMAs prior to altering
* @vp: The initialized vma_prepare struct
*/
static inline void vma_prepare(struct vma_prepare *vp)
{
vma_start_write(vp->vma);
if (vp->adj_next)
vma_start_write(vp->adj_next);
/* vp->insert is always a newly created VMA, no need for locking */
if (vp->remove)
vma_start_write(vp->remove);
if (vp->remove2)
vma_start_write(vp->remove2);
if (vp->file) {
uprobe_munmap(vp->vma, vp->vma->vm_start, vp->vma->vm_end);
if (vp->adj_next)
uprobe_munmap(vp->adj_next, vp->adj_next->vm_start,
vp->adj_next->vm_end);
i_mmap_lock_write(vp->mapping);
if (vp->insert && vp->insert->vm_file) {
/*
* Put into interval tree now, so instantiated pages
* are visible to arm/parisc __flush_dcache_page
* throughout; but we cannot insert into address
* space until vma start or end is updated.
*/
__vma_link_file(vp->insert,
vp->insert->vm_file->f_mapping);
}
}
if (vp->anon_vma) {
anon_vma_lock_write(vp->anon_vma);
anon_vma_interval_tree_pre_update_vma(vp->vma);
if (vp->adj_next)
anon_vma_interval_tree_pre_update_vma(vp->adj_next);
}
if (vp->file) {
flush_dcache_mmap_lock(vp->mapping);
vma_interval_tree_remove(vp->vma, &vp->mapping->i_mmap);
if (vp->adj_next)
vma_interval_tree_remove(vp->adj_next,
&vp->mapping->i_mmap);
}
}
/*
* vma_complete- Helper function for handling the unlocking after altering VMAs,
* or for inserting a VMA.
*
* @vp: The vma_prepare struct
* @vmi: The vma iterator
* @mm: The mm_struct
*/
static inline void vma_complete(struct vma_prepare *vp,
struct vma_iterator *vmi, struct mm_struct *mm)
{
if (vp->file) {
if (vp->adj_next)
vma_interval_tree_insert(vp->adj_next,
&vp->mapping->i_mmap);
vma_interval_tree_insert(vp->vma, &vp->mapping->i_mmap);
flush_dcache_mmap_unlock(vp->mapping);
}
if (vp->remove && vp->file) {
__remove_shared_vm_struct(vp->remove, vp->file, vp->mapping);
if (vp->remove2)
__remove_shared_vm_struct(vp->remove2, vp->file,
vp->mapping);
} else if (vp->insert) {
/*
* split_vma has split insert from vma, and needs
* us to insert it before dropping the locks
* (it may either follow vma or precede it).
*/
vma_iter_store(vmi, vp->insert);
mm->map_count++;
}
if (vp->anon_vma) {
anon_vma_interval_tree_post_update_vma(vp->vma);
if (vp->adj_next)
anon_vma_interval_tree_post_update_vma(vp->adj_next);
anon_vma_unlock_write(vp->anon_vma);
}
if (vp->file) {
i_mmap_unlock_write(vp->mapping);
uprobe_mmap(vp->vma);
if (vp->adj_next)
uprobe_mmap(vp->adj_next);
}
if (vp->remove) {
again:
vma_mark_detached(vp->remove, true);
if (vp->file) {
uprobe_munmap(vp->remove, vp->remove->vm_start,
vp->remove->vm_end);
fput(vp->file);
}
if (vp->remove->anon_vma)
anon_vma_merge(vp->vma, vp->remove);
mm->map_count--;
mpol_put(vma_policy(vp->remove));
if (!vp->remove2)
WARN_ON_ONCE(vp->vma->vm_end < vp->remove->vm_end);
vm_area_free(vp->remove);
/*
* In mprotect's case 6 (see comments on vma_merge),
* we are removing both mid and next vmas
*/
if (vp->remove2) {
vp->remove = vp->remove2;
vp->remove2 = NULL;
goto again;
}
}
if (vp->insert && vp->file)
uprobe_mmap(vp->insert);
}
/*
* dup_anon_vma() - Helper function to duplicate anon_vma
* @dst: The destination VMA
* @src: The source VMA
*
* Returns: 0 on success.
*/
static inline int dup_anon_vma(struct vm_area_struct *dst,
struct vm_area_struct *src)
{
/*
* Easily overlooked: when mprotect shifts the boundary, make sure the
* expanding vma has anon_vma set if the shrinking vma had, to cover any
* anon pages imported.
*/
if (src->anon_vma && !dst->anon_vma) {
dst->anon_vma = src->anon_vma;
return anon_vma_clone(dst, src);
}
return 0;
}
/*
* vma_expand - Expand an existing VMA
*
* @vmi: The vma iterator
* @vma: The vma to expand
* @start: The start of the vma
* @end: The exclusive end of the vma
* @pgoff: The page offset of vma
* @next: The current of next vma.
*
* Expand @vma to @start and @end. Can expand off the start and end. Will
* expand over @next if it's different from @vma and @end == @next->vm_end.
* Checking if the @vma can expand and merge with @next needs to be handled by
* the caller.
*
* Returns: 0 on success
*/
int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,
unsigned long start, unsigned long end, pgoff_t pgoff,
struct vm_area_struct *next)
{
bool remove_next = false;
struct vma_prepare vp;
if (next && (vma != next) && (end == next->vm_end)) {
int ret;
remove_next = true;
ret = dup_anon_vma(vma, next);
if (ret)
return ret;
}
init_multi_vma_prep(&vp, vma, NULL, remove_next ? next : NULL, NULL);
/* Not merging but overwriting any part of next is not handled. */
VM_WARN_ON(next && !vp.remove &&
next != vma && end > next->vm_start);
/* Only handles expanding */
VM_WARN_ON(vma->vm_start < start || vma->vm_end > end);
if (vma_iter_prealloc(vmi))
goto nomem;
vma_prepare(&vp);
vma_adjust_trans_huge(vma, start, end, 0);
/* VMA iterator points to previous, so set to start if necessary */
if (vma_iter_addr(vmi) != start)
vma_iter_set(vmi, start);
vma->vm_start = start;
vma->vm_end = end;
vma->vm_pgoff = pgoff;
/* Note: mas must be pointing to the expanding VMA */
vma_iter_store(vmi, vma);
vma_complete(&vp, vmi, vma->vm_mm);
validate_mm(vma->vm_mm);
return 0;
nomem:
return -ENOMEM;
}
/*
* vma_shrink() - Reduce an existing VMAs memory area
* @vmi: The vma iterator
* @vma: The VMA to modify
* @start: The new start
* @end: The new end
*
* Returns: 0 on success, -ENOMEM otherwise
*/
int vma_shrink(struct vma_iterator *vmi, struct vm_area_struct *vma,
unsigned long start, unsigned long end, pgoff_t pgoff)
{
struct vma_prepare vp;
WARN_ON((vma->vm_start != start) && (vma->vm_end != end));
if (vma_iter_prealloc(vmi))
return -ENOMEM;
init_vma_prep(&vp, vma);
vma_prepare(&vp);
vma_adjust_trans_huge(vma, start, end, 0);
if (vma->vm_start < start)
vma_iter_clear(vmi, vma->vm_start, start);
if (vma->vm_end > end)
vma_iter_clear(vmi, end, vma->vm_end);
vma->vm_start = start;
vma->vm_end = end;
vma->vm_pgoff = pgoff;
vma_complete(&vp, vmi, vma->vm_mm);
validate_mm(vma->vm_mm);
return 0;
}
/*
* If the vma has a ->close operation then the driver probably needs to release
* per-vma resources, so we don't attempt to merge those if the caller indicates
* the current vma may be removed as part of the merge.
*/
static inline bool is_mergeable_vma(struct vm_area_struct *vma,
struct file *file, unsigned long vm_flags,
struct vm_userfaultfd_ctx vm_userfaultfd_ctx,
struct anon_vma_name *anon_name, bool may_remove_vma)
{
/*
* VM_SOFTDIRTY should not prevent from VMA merging, if we
* match the flags but dirty bit -- the caller should mark
* merged VMA as dirty. If dirty bit won't be excluded from
* comparison, we increase pressure on the memory system forcing
* the kernel to generate new VMAs when old one could be
* extended instead.
*/
if ((vma->vm_flags ^ vm_flags) & ~VM_SOFTDIRTY)
return false;
if (vma->vm_file != file)
return false;
if (may_remove_vma && vma->vm_ops && vma->vm_ops->close)
return false;
if (!is_mergeable_vm_userfaultfd_ctx(vma, vm_userfaultfd_ctx))
return false;
if (!anon_vma_name_eq(anon_vma_name(vma), anon_name))
return false;
return true;
}
static inline bool is_mergeable_anon_vma(struct anon_vma *anon_vma1,
struct anon_vma *anon_vma2, struct vm_area_struct *vma)
{
/*
* The list_is_singular() test is to avoid merging VMA cloned from
* parents. This can improve scalability caused by anon_vma lock.
*/
if ((!anon_vma1 || !anon_vma2) && (!vma ||
list_is_singular(&vma->anon_vma_chain)))
return true;
return anon_vma1 == anon_vma2;
}
/*
* Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
* in front of (at a lower virtual address and file offset than) the vma.
*
* We cannot merge two vmas if they have differently assigned (non-NULL)
* anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
*
* We don't check here for the merged mmap wrapping around the end of pagecache
* indices (16TB on ia32) because do_mmap() does not permit mmap's which
* wrap, nor mmaps which cover the final page at index -1UL.
*
* We assume the vma may be removed as part of the merge.
*/
static bool
can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
struct anon_vma *anon_vma, struct file *file,
pgoff_t vm_pgoff, struct vm_userfaultfd_ctx vm_userfaultfd_ctx,
struct anon_vma_name *anon_name)
{
if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx, anon_name, true) &&
is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
if (vma->vm_pgoff == vm_pgoff)
return true;
}
return false;
}
/*
* Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
* beyond (at a higher virtual address and file offset than) the vma.
*
* We cannot merge two vmas if they have differently assigned (non-NULL)
* anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
*
* We assume that vma is not removed as part of the merge.
*/
static bool
can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
struct anon_vma *anon_vma, struct file *file,
pgoff_t vm_pgoff, struct vm_userfaultfd_ctx vm_userfaultfd_ctx,
struct anon_vma_name *anon_name)
{
if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx, anon_name, false) &&
is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
pgoff_t vm_pglen;
vm_pglen = vma_pages(vma);
if (vma->vm_pgoff + vm_pglen == vm_pgoff)
return true;
}
return false;
}
/*
* Given a mapping request (addr,end,vm_flags,file,pgoff,anon_name),
* figure out whether that can be merged with its predecessor or its
* successor. Or both (it neatly fills a hole).
*
* In most cases - when called for mmap, brk or mremap - [addr,end) is
* certain not to be mapped by the time vma_merge is called; but when
* called for mprotect, it is certain to be already mapped (either at
* an offset within prev, or at the start of next), and the flags of
* this area are about to be changed to vm_flags - and the no-change
* case has already been eliminated.
*
* The following mprotect cases have to be considered, where **** is
* the area passed down from mprotect_fixup, never extending beyond one
* vma, PPPP is the previous vma, CCCC is a concurrent vma that starts
* at the same address as **** and is of the same or larger span, and
* NNNN the next vma after ****:
*
* **** **** ****
* PPPPPPNNNNNN PPPPPPNNNNNN PPPPPPCCCCCC
* cannot merge might become might become
* PPNNNNNNNNNN PPPPPPPPPPCC
* mmap, brk or case 4 below case 5 below
* mremap move:
* **** ****
* PPPP NNNN PPPPCCCCNNNN
* might become might become
* PPPPPPPPPPPP 1 or PPPPPPPPPPPP 6 or
* PPPPPPPPNNNN 2 or PPPPPPPPNNNN 7 or
* PPPPNNNNNNNN 3 PPPPNNNNNNNN 8
*
* It is important for case 8 that the vma CCCC overlapping the
* region **** is never going to extended over NNNN. Instead NNNN must
* be extended in region **** and CCCC must be removed. This way in
* all cases where vma_merge succeeds, the moment vma_merge drops the
* rmap_locks, the properties of the merged vma will be already
* correct for the whole merged range. Some of those properties like
* vm_page_prot/vm_flags may be accessed by rmap_walks and they must
* be correct for the whole merged range immediately after the
* rmap_locks are released. Otherwise if NNNN would be removed and
* CCCC would be extended over the NNNN range, remove_migration_ptes
* or other rmap walkers (if working on addresses beyond the "end"
* parameter) may establish ptes with the wrong permissions of CCCC
* instead of the right permissions of NNNN.
*
* In the code below:
* PPPP is represented by *prev
* CCCC is represented by *curr or not represented at all (NULL)
* NNNN is represented by *next or not represented at all (NULL)
* **** is not represented - it will be merged and the vma containing the
* area is returned, or the function will return NULL
*/
struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
struct vm_area_struct *prev, unsigned long addr,
unsigned long end, unsigned long vm_flags,
struct anon_vma *anon_vma, struct file *file,
pgoff_t pgoff, struct mempolicy *policy,
struct vm_userfaultfd_ctx vm_userfaultfd_ctx,
struct anon_vma_name *anon_name)
{
struct vm_area_struct *curr, *next, *res;
struct vm_area_struct *vma, *adjust, *remove, *remove2;
struct vma_prepare vp;
pgoff_t vma_pgoff;
int err = 0;
bool merge_prev = false;
bool merge_next = false;
bool vma_expanded = false;
unsigned long vma_start = addr;
unsigned long vma_end = end;
pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
long adj_start = 0;
validate_mm(mm);
/*
* We later require that vma->vm_flags == vm_flags,
* so this tests vma->vm_flags & VM_SPECIAL, too.
*/
if (vm_flags & VM_SPECIAL)
return NULL;
/* Does the input range span an existing VMA? (cases 5 - 8) */
curr = find_vma_intersection(mm, prev ? prev->vm_end : 0, end);
if (!curr || /* cases 1 - 4 */
end == curr->vm_end) /* cases 6 - 8, adjacent VMA */
next = vma_lookup(mm, end);
else
next = NULL; /* case 5 */
if (prev) {
vma_start = prev->vm_start;
vma_pgoff = prev->vm_pgoff;
/* Can we merge the predecessor? */
if (addr == prev->vm_end && mpol_equal(vma_policy(prev), policy)
&& can_vma_merge_after(prev, vm_flags, anon_vma, file,
pgoff, vm_userfaultfd_ctx, anon_name)) {
merge_prev = true;
vma_prev(vmi);
}
}
/* Can we merge the successor? */
if (next && mpol_equal(policy, vma_policy(next)) &&
can_vma_merge_before(next, vm_flags, anon_vma, file, pgoff+pglen,
vm_userfaultfd_ctx, anon_name)) {
merge_next = true;
}
/* Verify some invariant that must be enforced by the caller. */
VM_WARN_ON(prev && addr <= prev->vm_start);
VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end));
VM_WARN_ON(addr >= end);
if (!merge_prev && !merge_next)
return NULL; /* Not mergeable. */
res = vma = prev;
remove = remove2 = adjust = NULL;
/* Can we merge both the predecessor and the successor? */
if (merge_prev && merge_next &&
is_mergeable_anon_vma(prev->anon_vma, next->anon_vma, NULL)) {
remove = next; /* case 1 */
vma_end = next->vm_end;
err = dup_anon_vma(prev, next);
if (curr) { /* case 6 */
remove = curr;
remove2 = next;
if (!next->anon_vma)
err = dup_anon_vma(prev, curr);
}
} else if (merge_prev) { /* case 2 */
if (curr) {
err = dup_anon_vma(prev, curr);
if (end == curr->vm_end) { /* case 7 */
remove = curr;
} else { /* case 5 */
adjust = curr;
adj_start = (end - curr->vm_start);
}
}
} else { /* merge_next */
res = next;
if (prev && addr < prev->vm_end) { /* case 4 */
vma_end = addr;
adjust = next;
adj_start = -(prev->vm_end - addr);
err = dup_anon_vma(next, prev);
} else {
/*
* Note that cases 3 and 8 are the ONLY ones where prev
* is permitted to be (but is not necessarily) NULL.
*/
vma = next; /* case 3 */
vma_start = addr;
vma_end = next->vm_end;
vma_pgoff = next->vm_pgoff - pglen;
if (curr) { /* case 8 */
vma_pgoff = curr->vm_pgoff;
remove = curr;
err = dup_anon_vma(next, curr);
}
}
}
/* Error in anon_vma clone. */
if (err)
return NULL;
if (vma_iter_prealloc(vmi))
return NULL;
init_multi_vma_prep(&vp, vma, adjust, remove, remove2);
VM_WARN_ON(vp.anon_vma && adjust && adjust->anon_vma &&
vp.anon_vma != adjust->anon_vma);
vma_prepare(&vp);
vma_adjust_trans_huge(vma, vma_start, vma_end, adj_start);
if (vma_start < vma->vm_start || vma_end > vma->vm_end)
vma_expanded = true;
vma->vm_start = vma_start;
vma->vm_end = vma_end;
vma->vm_pgoff = vma_pgoff;
if (vma_expanded)
vma_iter_store(vmi, vma);
if (adj_start) {
adjust->vm_start += adj_start;
adjust->vm_pgoff += adj_start >> PAGE_SHIFT;
if (adj_start < 0) {
WARN_ON(vma_expanded);
vma_iter_store(vmi, next);
}
}
vma_complete(&vp, vmi, mm);
vma_iter_free(vmi);
validate_mm(mm);
khugepaged_enter_vma(res, vm_flags);
return res;
}
/*
* Rough compatibility check to quickly see if it's even worth looking
* at sharing an anon_vma.
*
* They need to have the same vm_file, and the flags can only differ
* in things that mprotect may change.
*
* NOTE! The fact that we share an anon_vma doesn't _have_ to mean that
* we can merge the two vma's. For example, we refuse to merge a vma if
* there is a vm_ops->close() function, because that indicates that the
* driver is doing some kind of reference counting. But that doesn't
* really matter for the anon_vma sharing case.
*/
static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *b)
{
return a->vm_end == b->vm_start &&
mpol_equal(vma_policy(a), vma_policy(b)) &&
a->vm_file == b->vm_file &&
!((a->vm_flags ^ b->vm_flags) & ~(VM_ACCESS_FLAGS | VM_SOFTDIRTY)) &&
b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT);
}
/*
* Do some basic sanity checking to see if we can re-use the anon_vma
* from 'old'. The 'a'/'b' vma's are in VM order - one of them will be
* the same as 'old', the other will be the new one that is trying
* to share the anon_vma.
*
* NOTE! This runs with mmap_lock held for reading, so it is possible that
* the anon_vma of 'old' is concurrently in the process of being set up
* by another page fault trying to merge _that_. But that's ok: if it
* is being set up, that automatically means that it will be a singleton
* acceptable for merging, so we can do all of this optimistically. But
* we do that READ_ONCE() to make sure that we never re-load the pointer.
*
* IOW: that the "list_is_singular()" test on the anon_vma_chain only
* matters for the 'stable anon_vma' case (ie the thing we want to avoid
* is to return an anon_vma that is "complex" due to having gone through
* a fork).
*
* We also make sure that the two vma's are compatible (adjacent,
* and with the same memory policies). That's all stable, even with just
* a read lock on the mmap_lock.
*/
static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_area_struct *a, struct vm_area_struct *b)
{
if (anon_vma_compatible(a, b)) {
struct anon_vma *anon_vma = READ_ONCE(old->anon_vma);
if (anon_vma && list_is_singular(&old->anon_vma_chain))
return anon_vma;
}
return NULL;
}
/*
* find_mergeable_anon_vma is used by anon_vma_prepare, to check
* neighbouring vmas for a suitable anon_vma, before it goes off
* to allocate a new anon_vma. It checks because a repetitive
* sequence of mprotects and faults may otherwise lead to distinct
* anon_vmas being allocated, preventing vma merge in subsequent
* mprotect.
*/
struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
{
MA_STATE(mas, &vma->vm_mm->mm_mt, vma->vm_end, vma->vm_end);
struct anon_vma *anon_vma = NULL;
struct vm_area_struct *prev, *next;
/* Try next first. */
next = mas_walk(&mas);
if (next) {
anon_vma = reusable_anon_vma(next, vma, next);
if (anon_vma)
return anon_vma;
}
prev = mas_prev(&mas, 0);
VM_BUG_ON_VMA(prev != vma, vma);
prev = mas_prev(&mas, 0);
/* Try prev next. */
if (prev)
anon_vma = reusable_anon_vma(prev, prev, vma);
/*
* We might reach here with anon_vma == NULL if we can't find
* any reusable anon_vma.
* There's no absolute need to look only at touching neighbours:
* we could search further afield for "compatible" anon_vmas.
* But it would probably just be a waste of time searching,
* or lead to too many vmas hanging off the same anon_vma.
* We're trying to allow mprotect remerging later on,
* not trying to minimize memory used for anon_vmas.
*/
return anon_vma;
}
/*
* If a hint addr is less than mmap_min_addr change hint to be as
* low as possible but still greater than mmap_min_addr
*/
static inline unsigned long round_hint_to_min(unsigned long hint)
{
hint &= PAGE_MASK;
if (((void *)hint != NULL) &&
(hint < mmap_min_addr))
return PAGE_ALIGN(mmap_min_addr);
return hint;
}
bool mlock_future_ok(struct mm_struct *mm, unsigned long flags,
unsigned long bytes)
{
unsigned long locked_pages, limit_pages;
if (!(flags & VM_LOCKED) || capable(CAP_IPC_LOCK))
return true;
locked_pages = bytes >> PAGE_SHIFT;
locked_pages += mm->locked_vm;
limit_pages = rlimit(RLIMIT_MEMLOCK);
limit_pages >>= PAGE_SHIFT;
return locked_pages <= limit_pages;
}
static inline u64 file_mmap_size_max(struct file *file, struct inode *inode)
{
if (S_ISREG(inode->i_mode))
return MAX_LFS_FILESIZE;
if (S_ISBLK(inode->i_mode))
return MAX_LFS_FILESIZE;
if (S_ISSOCK(inode->i_mode))
return MAX_LFS_FILESIZE;
/* Special "we do even unsigned file positions" case */
if (file->f_mode & FMODE_UNSIGNED_OFFSET)
return 0;
/* Yes, random drivers might want more. But I'm tired of buggy drivers */
return ULONG_MAX;
}
static inline bool file_mmap_ok(struct file *file, struct inode *inode,
unsigned long pgoff, unsigned long len)
{
u64 maxsize = file_mmap_size_max(file, inode);
if (maxsize && len > maxsize)
return false;
maxsize -= len;
if (pgoff > maxsize >> PAGE_SHIFT)
return false;
return true;
}
/*
* The caller must write-lock current->mm->mmap_lock.
*/
unsigned long do_mmap(struct file *file, unsigned long addr,
unsigned long len, unsigned long prot,
unsigned long flags, unsigned long pgoff,
unsigned long *populate, struct list_head *uf)
{
struct mm_struct *mm = current->mm;
vm_flags_t vm_flags;
int pkey = 0;
validate_mm(mm);
*populate = 0;
if (!len)
return -EINVAL;
/*
* Does the application expect PROT_READ to imply PROT_EXEC?
*
* (the exception is when the underlying filesystem is noexec
* mounted, in which case we dont add PROT_EXEC.)
*/
if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
if (!(file && path_noexec(&file->f_path)))
prot |= PROT_EXEC;
/* force arch specific MAP_FIXED handling in get_unmapped_area */
if (flags & MAP_FIXED_NOREPLACE)
flags |= MAP_FIXED;
if (!(flags & MAP_FIXED))
addr = round_hint_to_min(addr);
/* Careful about overflows.. */
len = PAGE_ALIGN(len);
if (!len)
return -ENOMEM;
/* offset overflow? */
if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
return -EOVERFLOW;
/* Too many mappings? */
if (mm->map_count > sysctl_max_map_count)
return -ENOMEM;
/* Obtain the address to map to. we verify (or select) it and ensure
* that it represents a valid section of the address space.
*/
addr = get_unmapped_area(file, addr, len, pgoff, flags);
if (IS_ERR_VALUE(addr))
return addr;
if (flags & MAP_FIXED_NOREPLACE) {
if (find_vma_intersection(mm, addr, addr + len))
return -EEXIST;
}
if (prot == PROT_EXEC) {
pkey = execute_only_pkey(mm);
if (pkey < 0)
pkey = 0;
}
/* Do simple checking here so the lower-level routines won't have
* to. we assume access permissions have been handled by the open
* of the memory object, so we don't do any here.
*/
vm_flags = calc_vm_prot_bits(prot, pkey) | calc_vm_flag_bits(flags) |
mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
if (flags & MAP_LOCKED)
if (!can_do_mlock())
return -EPERM;
if (!mlock_future_ok(mm, vm_flags, len))
return -EAGAIN;
if (file) {
struct inode *inode = file_inode(file);
unsigned long flags_mask;
if (!file_mmap_ok(file, inode, pgoff, len))
return -EOVERFLOW;
flags_mask = LEGACY_MAP_MASK | file->f_op->mmap_supported_flags;
switch (flags & MAP_TYPE) {
case MAP_SHARED:
/*
* Force use of MAP_SHARED_VALIDATE with non-legacy
* flags. E.g. MAP_SYNC is dangerous to use with
* MAP_SHARED as you don't know which consistency model
* you will get. We silently ignore unsupported flags
* with MAP_SHARED to preserve backward compatibility.
*/
flags &= LEGACY_MAP_MASK;
fallthrough;
case MAP_SHARED_VALIDATE:
if (flags & ~flags_mask)
return -EOPNOTSUPP;
if (prot & PROT_WRITE) {
if (!(file->f_mode & FMODE_WRITE))
return -EACCES;
if (IS_SWAPFILE(file->f_mapping->host))
return -ETXTBSY;
}
/*
* Make sure we don't allow writing to an append-only
* file..
*/
if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE))
return -EACCES;
vm_flags |= VM_SHARED | VM_MAYSHARE;
if (!(file->f_mode & FMODE_WRITE))
vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
fallthrough;
case MAP_PRIVATE:
if (!(file->f_mode & FMODE_READ))
return -EACCES;
if (path_noexec(&file->f_path)) {
if (vm_flags & VM_EXEC)
return -EPERM;
vm_flags &= ~VM_MAYEXEC;
}
if (!file->f_op->mmap)
return -ENODEV;
if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
return -EINVAL;
break;
default:
return -EINVAL;
}
} else {
switch (flags & MAP_TYPE) {
case MAP_SHARED:
if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
return -EINVAL;
/*
* Ignore pgoff.
*/
pgoff = 0;
vm_flags |= VM_SHARED | VM_MAYSHARE;
break;
case MAP_PRIVATE:
/*
* Set pgoff according to addr for anon_vma.
*/
pgoff = addr >> PAGE_SHIFT;
break;
default:
return -EINVAL;
}
}
/*
* Set 'VM_NORESERVE' if we should not account for the
* memory use of this mapping.
*/
if (flags & MAP_NORESERVE) {
/* We honor MAP_NORESERVE if allowed to overcommit */
if (sysctl_overcommit_memory != OVERCOMMIT_NEVER)
vm_flags |= VM_NORESERVE;
/* hugetlb applies strict overcommit unless MAP_NORESERVE */
if (file && is_file_hugepages(file))
vm_flags |= VM_NORESERVE;
}
addr = mmap_region(file, addr, len, vm_flags, pgoff, uf);
if (!IS_ERR_VALUE(addr) &&
((vm_flags & VM_LOCKED) ||
(flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE))
*populate = len;
return addr;
}
unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
unsigned long prot, unsigned long flags,
unsigned long fd, unsigned long pgoff)
{
struct file *file = NULL;
unsigned long retval;
if (!(flags & MAP_ANONYMOUS)) {
audit_mmap_fd(fd, flags);
file = fget(fd);
if (!file)
return -EBADF;
if (is_file_hugepages(file)) {
len = ALIGN(len, huge_page_size(hstate_file(file)));
} else if (unlikely(flags & MAP_HUGETLB)) {
retval = -EINVAL;
goto out_fput;
}
} else if (flags & MAP_HUGETLB) {
struct hstate *hs;
hs = hstate_sizelog((flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
if (!hs)
return -EINVAL;
len = ALIGN(len, huge_page_size(hs));
/*
* VM_NORESERVE is used because the reservations will be
* taken when vm_ops->mmap() is called
*/
file = hugetlb_file_setup(HUGETLB_ANON_FILE, len,
VM_NORESERVE,
HUGETLB_ANONHUGE_INODE,
(flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
if (IS_ERR(file))
return PTR_ERR(file);
}
retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
out_fput:
if (file)
fput(file);
return retval;
}
SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
unsigned long, prot, unsigned long, flags,
unsigned long, fd, unsigned long, pgoff)
{
return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
}
#ifdef __ARCH_WANT_SYS_OLD_MMAP
struct mmap_arg_struct {
unsigned long addr;
unsigned long len;
unsigned long prot;
unsigned long flags;
unsigned long fd;
unsigned long offset;
};
SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
{
struct mmap_arg_struct a;
if (copy_from_user(&a, arg, sizeof(a)))
return -EFAULT;
if (offset_in_page(a.offset))
return -EINVAL;
return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
a.offset >> PAGE_SHIFT);
}
#endif /* __ARCH_WANT_SYS_OLD_MMAP */
static bool vm_ops_needs_writenotify(const struct vm_operations_struct *vm_ops)
{
return vm_ops && (vm_ops->page_mkwrite || vm_ops->pfn_mkwrite);
}
static bool vma_is_shared_writable(struct vm_area_struct *vma)
{
return (vma->vm_flags & (VM_WRITE | VM_SHARED)) ==
(VM_WRITE | VM_SHARED);
}
static bool vma_fs_can_writeback(struct vm_area_struct *vma)
{
/* No managed pages to writeback. */
if (vma->vm_flags & VM_PFNMAP)
return false;
return vma->vm_file && vma->vm_file->f_mapping &&
mapping_can_writeback(vma->vm_file->f_mapping);
}
/*
* Does this VMA require the underlying folios to have their dirty state
* tracked?
*/
bool vma_needs_dirty_tracking(struct vm_area_struct *vma)
{
/* Only shared, writable VMAs require dirty tracking. */
if (!vma_is_shared_writable(vma))
return false;
/* Does the filesystem need to be notified? */
if (vm_ops_needs_writenotify(vma->vm_ops))
return true;
/*
* Even if the filesystem doesn't indicate a need for writenotify, if it
* can writeback, dirty tracking is still required.
*/
return vma_fs_can_writeback(vma);
}
/*
* Some shared mappings will want the pages marked read-only
* to track write events. If so, we'll downgrade vm_page_prot
* to the private version (using protection_map[] without the
* VM_SHARED bit).
*/
int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot)
{
/* If it was private or non-writable, the write bit is already clear */
if (!vma_is_shared_writable(vma))
return 0;
/* The backer wishes to know when pages are first written to? */
if (vm_ops_needs_writenotify(vma->vm_ops))
return 1;
/* The open routine did something to the protections that pgprot_modify
* won't preserve? */
if (pgprot_val(vm_page_prot) !=
pgprot_val(vm_pgprot_modify(vm_page_prot, vma->vm_flags)))
return 0;
/*
* Do we need to track softdirty? hugetlb does not support softdirty
* tracking yet.
*/
if (vma_soft_dirty_enabled(vma) && !is_vm_hugetlb_page(vma))
return 1;
/* Do we need write faults for uffd-wp tracking? */
if (userfaultfd_wp(vma))
return 1;
/* Can the mapping track the dirty pages? */
return vma_fs_can_writeback(vma);
}
/*
* We account for memory if it's a private writeable mapping,
* not hugepages and VM_NORESERVE wasn't set.
*/
static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags)
{
/*
* hugetlb has its own accounting separate from the core VM
* VM_HUGETLB may not be set yet so we cannot check for that flag.
*/
if (file && is_file_hugepages(file))
return 0;
return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
}
/**
* unmapped_area() - Find an area between the low_limit and the high_limit with
* the correct alignment and offset, all from @info. Note: current->mm is used
* for the search.
*
* @info: The unmapped area information including the range [low_limit -
* high_limit), the alignment offset and mask.
*
* Return: A memory address or -ENOMEM.
*/
static unsigned long unmapped_area(struct vm_unmapped_area_info *info)
{
unsigned long length, gap;
unsigned long low_limit, high_limit;
struct vm_area_struct *tmp;
MA_STATE(mas, &current->mm->mm_mt, 0, 0);
/* Adjust search length to account for worst case alignment overhead */
length = info->length + info->align_mask;
if (length < info->length)
return -ENOMEM;
low_limit = info->low_limit;
if (low_limit < mmap_min_addr)
low_limit = mmap_min_addr;
high_limit = info->high_limit;
retry:
if (mas_empty_area(&mas, low_limit, high_limit - 1, length))
return -ENOMEM;
gap = mas.index;
gap += (info->align_offset - gap) & info->align_mask;
tmp = mas_next(&mas, ULONG_MAX);
if (tmp && (tmp->vm_flags & VM_GROWSDOWN)) { /* Avoid prev check if possible */
if (vm_start_gap(tmp) < gap + length - 1) {
low_limit = tmp->vm_end;
mas_reset(&mas);
goto retry;
}
} else {
tmp = mas_prev(&mas, 0);
if (tmp && vm_end_gap(tmp) > gap) {
low_limit = vm_end_gap(tmp);
mas_reset(&mas);
goto retry;
}
}
return gap;
}
/**
* unmapped_area_topdown() - Find an area between the low_limit and the
* high_limit with the correct alignment and offset at the highest available
* address, all from @info. Note: current->mm is used for the search.
*
* @info: The unmapped area information including the range [low_limit -
* high_limit), the alignment offset and mask.
*
* Return: A memory address or -ENOMEM.
*/
static unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
{
unsigned long length, gap, gap_end;
unsigned long low_limit, high_limit;
struct vm_area_struct *tmp;
MA_STATE(mas, &current->mm->mm_mt, 0, 0);
/* Adjust search length to account for worst case alignment overhead */
length = info->length + info->align_mask;
if (length < info->length)
return -ENOMEM;
low_limit = info->low_limit;
if (low_limit < mmap_min_addr)
low_limit = mmap_min_addr;
high_limit = info->high_limit;
retry:
if (mas_empty_area_rev(&mas, low_limit, high_limit - 1, length))
return -ENOMEM;
gap = mas.last + 1 - info->length;
gap -= (gap - info->align_offset) & info->align_mask;
gap_end = mas.last;
tmp = mas_next(&mas, ULONG_MAX);
if (tmp && (tmp->vm_flags & VM_GROWSDOWN)) { /* Avoid prev check if possible */
if (vm_start_gap(tmp) <= gap_end) {
high_limit = vm_start_gap(tmp);
mas_reset(&mas);
goto retry;
}
} else {
tmp = mas_prev(&mas, 0);
if (tmp && vm_end_gap(tmp) > gap) {
high_limit = tmp->vm_start;
mas_reset(&mas);
goto retry;
}
}
return gap;
}
/*
* Search for an unmapped address range.
*
* We are looking for a range that:
* - does not intersect with any VMA;
* - is contained within the [low_limit, high_limit) interval;
* - is at least the desired size.
* - satisfies (begin_addr & align_mask) == (align_offset & align_mask)
*/
unsigned long vm_unmapped_area(struct vm_unmapped_area_info *info)
{
unsigned long addr;
if (info->flags & VM_UNMAPPED_AREA_TOPDOWN)
addr = unmapped_area_topdown(info);
else
addr = unmapped_area(info);
trace_vm_unmapped_area(addr, info);
return addr;
}
/* Get an address range which is currently unmapped.
* For shmat() with addr=0.
*
* Ugly calling convention alert:
* Return value with the low bits set means error value,
* ie
* if (ret & ~PAGE_MASK)
* error = ret;
*
* This function "knows" that -ENOMEM has the bits set.
*/
unsigned long
generic_get_unmapped_area(struct file *filp, unsigned long addr,
unsigned long len, unsigned long pgoff,
unsigned long flags)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma, *prev;
struct vm_unmapped_area_info info;
const unsigned long mmap_end = arch_get_mmap_end(addr, len, flags);
if (len > mmap_end - mmap_min_addr)
return -ENOMEM;
if (flags & MAP_FIXED)
return addr;
if (addr) {
addr = PAGE_ALIGN(addr);
vma = find_vma_prev(mm, addr, &prev);
if (mmap_end - len >= addr && addr >= mmap_min_addr &&
(!vma || addr + len <= vm_start_gap(vma)) &&
(!prev || addr >= vm_end_gap(prev)))
return addr;
}
info.flags = 0;
info.length = len;
info.low_limit = mm->mmap_base;
info.high_limit = mmap_end;
info.align_mask = 0;
info.align_offset = 0;
return vm_unmapped_area(&info);
}
#ifndef HAVE_ARCH_UNMAPPED_AREA
unsigned long
arch_get_unmapped_area(struct file *filp, unsigned long addr,
unsigned long len, unsigned long pgoff,
unsigned long flags)
{
return generic_get_unmapped_area(filp, addr, len, pgoff, flags);
}
#endif
/*
* This mmap-allocator allocates new areas top-down from below the
* stack's low limit (the base):
*/
unsigned long
generic_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
unsigned long len, unsigned long pgoff,
unsigned long flags)
{
struct vm_area_struct *vma, *prev;
struct mm_struct *mm = current->mm;
struct vm_unmapped_area_info info;
const unsigned long mmap_end = arch_get_mmap_end(addr, len, flags);
/* requested length too big for entire address space */
if (len > mmap_end - mmap_min_addr)
return -ENOMEM;
if (flags & MAP_FIXED)
return addr;
/* requesting a specific address */
if (addr) {
addr = PAGE_ALIGN(addr);
vma = find_vma_prev(mm, addr, &prev);
if (mmap_end - len >= addr && addr >= mmap_min_addr &&
(!vma || addr + len <= vm_start_gap(vma)) &&
(!prev || addr >= vm_end_gap(prev)))
return addr;
}
info.flags = VM_UNMAPPED_AREA_TOPDOWN;
info.length = len;
info.low_limit = PAGE_SIZE;
info.high_limit = arch_get_mmap_base(addr, mm->mmap_base);
info.align_mask = 0;
info.align_offset = 0;
addr = vm_unmapped_area(&info);
/*
* A failed mmap() very likely causes application failure,
* so fall back to the bottom-up function here. This scenario
* can happen with large stack limits and large mmap()
* allocations.
*/
if (offset_in_page(addr)) {
VM_BUG_ON(addr != -ENOMEM);
info.flags = 0;
info.low_limit = TASK_UNMAPPED_BASE;
info.high_limit = mmap_end;
addr = vm_unmapped_area(&info);
}
return addr;
}
#ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
unsigned long
arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
unsigned long len, unsigned long pgoff,
unsigned long flags)
{
return generic_get_unmapped_area_topdown(filp, addr, len, pgoff, flags);
}
#endif
unsigned long
get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
unsigned long pgoff, unsigned long flags)
{
unsigned long (*get_area)(struct file *, unsigned long,
unsigned long, unsigned long, unsigned long);
unsigned long error = arch_mmap_check(addr, len, flags);
if (error)
return error;
/* Careful about overflows.. */
if (len > TASK_SIZE)
return -ENOMEM;
get_area = current->mm->get_unmapped_area;
if (file) {
if (file->f_op->get_unmapped_area)
get_area = file->f_op->get_unmapped_area;
} else if (flags & MAP_SHARED) {
/*
* mmap_region() will call shmem_zero_setup() to create a file,
* so use shmem's get_unmapped_area in case it can be huge.
* do_mmap() will clear pgoff, so match alignment.
*/
pgoff = 0;
get_area = shmem_get_unmapped_area;
}
addr = get_area(file, addr, len, pgoff, flags);
if (IS_ERR_VALUE(addr))
return addr;
if (addr > TASK_SIZE - len)
return -ENOMEM;
if (offset_in_page(addr))
return -EINVAL;
error = security_mmap_addr(addr);
return error ? error : addr;
}
EXPORT_SYMBOL(get_unmapped_area);
/**
* find_vma_intersection() - Look up the first VMA which intersects the interval
* @mm: The process address space.
* @start_addr: The inclusive start user address.
* @end_addr: The exclusive end user address.
*
* Returns: The first VMA within the provided range, %NULL otherwise. Assumes
* start_addr < end_addr.
*/
struct vm_area_struct *find_vma_intersection(struct mm_struct *mm,
unsigned long start_addr,
unsigned long end_addr)
{
unsigned long index = start_addr;
mmap_assert_locked(mm);
return mt_find(&mm->mm_mt, &index, end_addr - 1);
}
EXPORT_SYMBOL(find_vma_intersection);
/**
* find_vma() - Find the VMA for a given address, or the next VMA.
* @mm: The mm_struct to check
* @addr: The address
*
* Returns: The VMA associated with addr, or the next VMA.
* May return %NULL in the case of no VMA at addr or above.
*/
struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
{
unsigned long index = addr;
mmap_assert_locked(mm);
return mt_find(&mm->mm_mt, &index, ULONG_MAX);
}
EXPORT_SYMBOL(find_vma);
/**
* find_vma_prev() - Find the VMA for a given address, or the next vma and
* set %pprev to the previous VMA, if any.
* @mm: The mm_struct to check
* @addr: The address
* @pprev: The pointer to set to the previous VMA
*
* Note that RCU lock is missing here since the external mmap_lock() is used
* instead.
*
* Returns: The VMA associated with @addr, or the next vma.
* May return %NULL in the case of no vma at addr or above.
*/
struct vm_area_struct *
find_vma_prev(struct mm_struct *mm, unsigned long addr,
struct vm_area_struct **pprev)
{
struct vm_area_struct *vma;
MA_STATE(mas, &mm->mm_mt, addr, addr);
vma = mas_walk(&mas);
*pprev = mas_prev(&mas, 0);
if (!vma)
vma = mas_next(&mas, ULONG_MAX);
return vma;
}
/*
* Verify that the stack growth is acceptable and
* update accounting. This is shared with both the
* grow-up and grow-down cases.
*/
static int acct_stack_growth(struct vm_area_struct *vma,
unsigned long size, unsigned long grow)
{
struct mm_struct *mm = vma->vm_mm;
unsigned long new_start;
/* address space limit tests */
if (!may_expand_vm(mm, vma->vm_flags, grow))
return -ENOMEM;
/* Stack limit test */
if (size > rlimit(RLIMIT_STACK))
return -ENOMEM;
/* mlock limit tests */
if (!mlock_future_ok(mm, vma->vm_flags, grow << PAGE_SHIFT))
return -ENOMEM;
/* Check to ensure the stack will not grow into a hugetlb-only region */
new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :
vma->vm_end - size;
if (is_hugepage_only_range(vma->vm_mm, new_start, size))
return -EFAULT;
/*
* Overcommit.. This must be the final test, as it will
* update security statistics.
*/
if (security_vm_enough_memory_mm(mm, grow))
return -ENOMEM;
return 0;
}
#if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
/*
* PA-RISC uses this for its stack; IA64 for its Register Backing Store.
* vma is the last one with address > vma->vm_end. Have to extend vma.
*/
int expand_upwards(struct vm_area_struct *vma, unsigned long address)
{
struct mm_struct *mm = vma->vm_mm;
struct vm_area_struct *next;
unsigned long gap_addr;
int error = 0;
MA_STATE(mas, &mm->mm_mt, 0, 0);
if (!(vma->vm_flags & VM_GROWSUP))
return -EFAULT;
/* Guard against exceeding limits of the address space. */
address &= PAGE_MASK;
if (address >= (TASK_SIZE & PAGE_MASK))
return -ENOMEM;
address += PAGE_SIZE;
/* Enforce stack_guard_gap */
gap_addr = address + stack_guard_gap;
/* Guard against overflow */
if (gap_addr < address || gap_addr > TASK_SIZE)
gap_addr = TASK_SIZE;
next = find_vma_intersection(mm, vma->vm_end, gap_addr);
if (next && vma_is_accessible(next)) {
if (!(next->vm_flags & VM_GROWSUP))
return -ENOMEM;
/* Check that both stack segments have the same anon_vma? */
}
if (mas_preallocate(&mas, GFP_KERNEL))
return -ENOMEM;
/* We must make sure the anon_vma is allocated. */
if (unlikely(anon_vma_prepare(vma))) {
mas_destroy(&mas);
return -ENOMEM;
}
/*
* vma->vm_start/vm_end cannot change under us because the caller
* is required to hold the mmap_lock in read mode. We need the
* anon_vma lock to serialize against concurrent expand_stacks.
*/
anon_vma_lock_write(vma->anon_vma);
/* Somebody else might have raced and expanded it already */
if (address > vma->vm_end) {
unsigned long size, grow;
size = address - vma->vm_start;
grow = (address - vma->vm_end) >> PAGE_SHIFT;
error = -ENOMEM;
if (vma->vm_pgoff + (size >> PAGE_SHIFT) >= vma->vm_pgoff) {
error = acct_stack_growth(vma, size, grow);
if (!error) {
/*
* We only hold a shared mmap_lock lock here, so
* we need to protect against concurrent vma
* expansions. anon_vma_lock_write() doesn't
* help here, as we don't guarantee that all
* growable vmas in a mm share the same root
* anon vma. So, we reuse mm->page_table_lock
* to guard against concurrent vma expansions.
*/
spin_lock(&mm->page_table_lock);
if (vma->vm_flags & VM_LOCKED)
mm->locked_vm += grow;
vm_stat_account(mm, vma->vm_flags, grow);
anon_vma_interval_tree_pre_update_vma(vma);
vma->vm_end = address;
/* Overwrite old entry in mtree. */
mas_set_range(&mas, vma->vm_start, address - 1);
mas_store_prealloc(&mas, vma);
anon_vma_interval_tree_post_update_vma(vma);
spin_unlock(&mm->page_table_lock);
perf_event_mmap(vma);
}
}
}
anon_vma_unlock_write(vma->anon_vma);
khugepaged_enter_vma(vma, vma->vm_flags);
mas_destroy(&mas);
return error;
}
#endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
/*
* vma is the first one with address < vma->vm_start. Have to extend vma.
*/
int expand_downwards(struct vm_area_struct *vma, unsigned long address)
{
struct mm_struct *mm = vma->vm_mm;
MA_STATE(mas, &mm->mm_mt, vma->vm_start, vma->vm_start);
struct vm_area_struct *prev;
int error = 0;
address &= PAGE_MASK;
if (address < mmap_min_addr)
return -EPERM;
/* Enforce stack_guard_gap */
prev = mas_prev(&mas, 0);
/* Check that both stack segments have the same anon_vma? */
if (prev && !(prev->vm_flags & VM_GROWSDOWN) &&
vma_is_accessible(prev)) {
if (address - prev->vm_end < stack_guard_gap)
return -ENOMEM;
}
if (mas_preallocate(&mas, GFP_KERNEL))
return -ENOMEM;
/* We must make sure the anon_vma is allocated. */
if (unlikely(anon_vma_prepare(vma))) {
mas_destroy(&mas);
return -ENOMEM;
}
/*
* vma->vm_start/vm_end cannot change under us because the caller
* is required to hold the mmap_lock in read mode. We need the
* anon_vma lock to serialize against concurrent expand_stacks.
*/
anon_vma_lock_write(vma->anon_vma);
/* Somebody else might have raced and expanded it already */
if (address < vma->vm_start) {
unsigned long size, grow;
size = vma->vm_end - address;
grow = (vma->vm_start - address) >> PAGE_SHIFT;
error = -ENOMEM;
if (grow <= vma->vm_pgoff) {
error = acct_stack_growth(vma, size, grow);
if (!error) {
/*
* We only hold a shared mmap_lock lock here, so
* we need to protect against concurrent vma
* expansions. anon_vma_lock_write() doesn't
* help here, as we don't guarantee that all
* growable vmas in a mm share the same root
* anon vma. So, we reuse mm->page_table_lock
* to guard against concurrent vma expansions.
*/
spin_lock(&mm->page_table_lock);
if (vma->vm_flags & VM_LOCKED)
mm->locked_vm += grow;
vm_stat_account(mm, vma->vm_flags, grow);
anon_vma_interval_tree_pre_update_vma(vma);
vma->vm_start = address;
vma->vm_pgoff -= grow;
/* Overwrite old entry in mtree. */
mas_set_range(&mas, address, vma->vm_end - 1);
mas_store_prealloc(&mas, vma);
anon_vma_interval_tree_post_update_vma(vma);
spin_unlock(&mm->page_table_lock);
perf_event_mmap(vma);
}
}
}
anon_vma_unlock_write(vma->anon_vma);
khugepaged_enter_vma(vma, vma->vm_flags);
mas_destroy(&mas);
return error;
}
/* enforced gap between the expanding stack and other mappings. */
unsigned long stack_guard_gap = 256UL<<PAGE_SHIFT;
static int __init cmdline_parse_stack_guard_gap(char *p)
{
unsigned long val;
char *endptr;
val = simple_strtoul(p, &endptr, 10);
if (!*endptr)
stack_guard_gap = val << PAGE_SHIFT;
return 1;
}
__setup("stack_guard_gap=", cmdline_parse_stack_guard_gap);
#ifdef CONFIG_STACK_GROWSUP
int expand_stack(struct vm_area_struct *vma, unsigned long address)
{
return expand_upwards(vma, address);
}
struct vm_area_struct *
find_extend_vma(struct mm_struct *mm, unsigned long addr)
{
struct vm_area_struct *vma, *prev;
addr &= PAGE_MASK;
vma = find_vma_prev(mm, addr, &prev);
if (vma && (vma->vm_start <= addr))
return vma;
if (!prev || expand_stack(prev, addr))
return NULL;
if (prev->vm_flags & VM_LOCKED)
populate_vma_page_range(prev, addr, prev->vm_end, NULL);
return prev;
}
#else
int expand_stack(struct vm_area_struct *vma, unsigned long address)
{
return expand_downwards(vma, address);
}
struct vm_area_struct *
find_extend_vma(struct mm_struct *mm, unsigned long addr)
{
struct vm_area_struct *vma;
unsigned long start;
addr &= PAGE_MASK;
vma = find_vma(mm, addr);
if (!vma)
return NULL;
if (vma->vm_start <= addr)
return vma;
if (!(vma->vm_flags & VM_GROWSDOWN))
return NULL;
start = vma->vm_start;
if (expand_stack(vma, addr))
return NULL;
if (vma->vm_flags & VM_LOCKED)
populate_vma_page_range(vma, addr, start, NULL);
return vma;
}
#endif
EXPORT_SYMBOL_GPL(find_extend_vma);
/*
* Ok - we have the memory areas we should free on a maple tree so release them,
* and do the vma updates.
*
* Called with the mm semaphore held.
*/
static inline void remove_mt(struct mm_struct *mm, struct ma_state *mas)
{
unsigned long nr_accounted = 0;
struct vm_area_struct *vma;
/* Update high watermark before we lower total_vm */
update_hiwater_vm(mm);
mas_for_each(mas, vma, ULONG_MAX) {
long nrpages = vma_pages(vma);
if (vma->vm_flags & VM_ACCOUNT)
nr_accounted += nrpages;
vm_stat_account(mm, vma->vm_flags, -nrpages);
remove_vma(vma, false);
}
vm_unacct_memory(nr_accounted);
validate_mm(mm);
}
/*
* Get rid of page table information in the indicated region.
*
* Called with the mm semaphore held.
*/
static void unmap_region(struct mm_struct *mm, struct maple_tree *mt,
struct vm_area_struct *vma, struct vm_area_struct *prev,
struct vm_area_struct *next,
unsigned long start, unsigned long end, bool mm_wr_locked)
{
struct mmu_gather tlb;
lru_add_drain();
tlb_gather_mmu(&tlb, mm);
update_hiwater_rss(mm);
unmap_vmas(&tlb, mt, vma, start, end, mm_wr_locked);
free_pgtables(&tlb, mt, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
next ? next->vm_start : USER_PGTABLES_CEILING,
mm_wr_locked);
tlb_finish_mmu(&tlb);
}
/*
* __split_vma() bypasses sysctl_max_map_count checking. We use this where it
* has already been checked or doesn't make sense to fail.
* VMA Iterator will point to the end VMA.
*/
int __split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma,
unsigned long addr, int new_below)
{
struct vma_prepare vp;
struct vm_area_struct *new;
int err;
validate_mm(vma->vm_mm);
WARN_ON(vma->vm_start >= addr);
WARN_ON(vma->vm_end <= addr);
if (vma->vm_ops && vma->vm_ops->may_split) {
err = vma->vm_ops->may_split(vma, addr);
if (err)
return err;
}
new = vm_area_dup(vma);
if (!new)
return -ENOMEM;
err = -ENOMEM;
if (vma_iter_prealloc(vmi))
goto out_free_vma;
if (new_below) {
new->vm_end = addr;
} else {
new->vm_start = addr;
new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
}
err = vma_dup_policy(vma, new);
if (err)
goto out_free_vmi;
err = anon_vma_clone(new, vma);
if (err)
goto out_free_mpol;
if (new->vm_file)
get_file(new->vm_file);
if (new->vm_ops && new->vm_ops->open)
new->vm_ops->open(new);
init_vma_prep(&vp, vma);
vp.insert = new;
vma_prepare(&vp);
vma_adjust_trans_huge(vma, vma->vm_start, addr, 0);
if (new_below) {
vma->vm_start = addr;
vma->vm_pgoff += (addr - new->vm_start) >> PAGE_SHIFT;
} else {
vma->vm_end = addr;
}
/* vma_complete stores the new vma */
vma_complete(&vp, vmi, vma->vm_mm);
/* Success. */
if (new_below)
vma_next(vmi);
validate_mm(vma->vm_mm);
return 0;
out_free_mpol:
mpol_put(vma_policy(new));
out_free_vmi:
vma_iter_free(vmi);
out_free_vma:
vm_area_free(new);
validate_mm(vma->vm_mm);
return err;
}
/*
* Split a vma into two pieces at address 'addr', a new vma is allocated
* either for the first part or the tail.
*/
int split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma,
unsigned long addr, int new_below)
{
if (vma->vm_mm->map_count >= sysctl_max_map_count)
return -ENOMEM;
return __split_vma(vmi, vma, addr, new_below);
}
static inline int munmap_sidetree(struct vm_area_struct *vma,
struct ma_state *mas_detach)
{
vma_start_write(vma);
mas_set_range(mas_detach, vma->vm_start, vma->vm_end - 1);
if (mas_store_gfp(mas_detach, vma, GFP_KERNEL))
return -ENOMEM;
vma_mark_detached(vma, true);
if (vma->vm_flags & VM_LOCKED)
vma->vm_mm->locked_vm -= vma_pages(vma);
return 0;
}
/*
* do_vmi_align_munmap() - munmap the aligned region from @start to @end.
* @vmi: The vma iterator
* @vma: The starting vm_area_struct
* @mm: The mm_struct
* @start: The aligned start address to munmap.
* @end: The aligned end address to munmap.
* @uf: The userfaultfd list_head
* @downgrade: Set to true to attempt a write downgrade of the mmap_lock
*
* If @downgrade is true, check return code for potential release of the lock.
*/
static int
do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
struct mm_struct *mm, unsigned long start,
unsigned long end, struct list_head *uf, bool downgrade)
{
struct vm_area_struct *prev, *next = NULL;
struct maple_tree mt_detach;
int count = 0;
int error = -ENOMEM;
MA_STATE(mas_detach, &mt_detach, 0, 0);
mt_init_flags(&mt_detach, vmi->mas.tree->ma_flags & MT_FLAGS_LOCK_MASK);
mt_set_external_lock(&mt_detach, &mm->mmap_lock);
/*
* If we need to split any vma, do it now to save pain later.
*
* Note: mremap's move_vma VM_ACCOUNT handling assumes a partially
* unmapped vm_area_struct will remain in use: so lower split_vma
* places tmp vma above, and higher split_vma places tmp vma below.
*/
/* Does it split the first one? */
if (start > vma->vm_start) {
/*
* Make sure that map_count on return from munmap() will
* not exceed its limit; but let map_count go just above
* its limit temporarily, to help free resources as expected.
*/
if (end < vma->vm_end && mm->map_count >= sysctl_max_map_count)
goto map_count_exceeded;
error = __split_vma(vmi, vma, start, 0);
if (error)
goto start_split_failed;
vma = vma_iter_load(vmi);
}
prev = vma_prev(vmi);
if (unlikely((!prev)))
vma_iter_set(vmi, start);
/*
* Detach a range of VMAs from the mm. Using next as a temp variable as
* it is always overwritten.
*/
for_each_vma_range(*vmi, next, end) {
/* Does it split the end? */
if (next->vm_end > end) {
error = __split_vma(vmi, next, end, 0);
if (error)
goto end_split_failed;
}
error = munmap_sidetree(next, &mas_detach);
if (error)
goto munmap_sidetree_failed;
count++;
#ifdef CONFIG_DEBUG_VM_MAPLE_TREE
BUG_ON(next->vm_start < start);
BUG_ON(next->vm_start > end);
#endif
}
if (vma_iter_end(vmi) > end)
next = vma_iter_load(vmi);
if (!next)
next = vma_next(vmi);
if (unlikely(uf)) {
/*
* If userfaultfd_unmap_prep returns an error the vmas
* will remain split, but userland will get a
* highly unexpected error anyway. This is no
* different than the case where the first of the two
* __split_vma fails, but we don't undo the first
* split, despite we could. This is unlikely enough
* failure that it's not worth optimizing it for.
*/
error = userfaultfd_unmap_prep(mm, start, end, uf);
if (error)
goto userfaultfd_error;
}
#if defined(CONFIG_DEBUG_VM_MAPLE_TREE)
/* Make sure no VMAs are about to be lost. */
{
MA_STATE(test, &mt_detach, start, end - 1);
struct vm_area_struct *vma_mas, *vma_test;
int test_count = 0;
vma_iter_set(vmi, start);
rcu_read_lock();
vma_test = mas_find(&test, end - 1);
for_each_vma_range(*vmi, vma_mas, end) {
BUG_ON(vma_mas != vma_test);
test_count++;
vma_test = mas_next(&test, end - 1);
}
rcu_read_unlock();
BUG_ON(count != test_count);
}
#endif
/* Point of no return */
vma_iter_set(vmi, start);
if (vma_iter_clear_gfp(vmi, start, end, GFP_KERNEL))
return -ENOMEM;
mm->map_count -= count;
/*
* Do not downgrade mmap_lock if we are next to VM_GROWSDOWN or
* VM_GROWSUP VMA. Such VMAs can change their size under
* down_read(mmap_lock) and collide with the VMA we are about to unmap.
*/
if (downgrade) {
if (next && (next->vm_flags & VM_GROWSDOWN))
downgrade = false;
else if (prev && (prev->vm_flags & VM_GROWSUP))
downgrade = false;
else
mmap_write_downgrade(mm);
}
/*
* We can free page tables without write-locking mmap_lock because VMAs
* were isolated before we downgraded mmap_lock.
*/
unmap_region(mm, &mt_detach, vma, prev, next, start, end, !downgrade);
/* Statistics and freeing VMAs */
mas_set(&mas_detach, start);
remove_mt(mm, &mas_detach);
__mt_destroy(&mt_detach);
validate_mm(mm);
return downgrade ? 1 : 0;
userfaultfd_error:
munmap_sidetree_failed:
end_split_failed:
__mt_destroy(&mt_detach);
start_split_failed:
map_count_exceeded:
return error;
}
/*
* do_vmi_munmap() - munmap a given range.
* @vmi: The vma iterator
* @mm: The mm_struct
* @start: The start address to munmap
* @len: The length of the range to munmap
* @uf: The userfaultfd list_head
* @downgrade: set to true if the user wants to attempt to write_downgrade the
* mmap_lock
*
* This function takes a @mas that is either pointing to the previous VMA or set
* to MA_START and sets it up to remove the mapping(s). The @len will be
* aligned and any arch_unmap work will be preformed.
*
* Returns: -EINVAL on failure, 1 on success and unlock, 0 otherwise.
*/
int do_vmi_munmap(struct vma_iterator *vmi, struct mm_struct *mm,
unsigned long start, size_t len, struct list_head *uf,
bool downgrade)
{
unsigned long end;
struct vm_area_struct *vma;
if ((offset_in_page(start)) || start > TASK_SIZE || len > TASK_SIZE-start)
return -EINVAL;
end = start + PAGE_ALIGN(len);
if (end == start)
return -EINVAL;
/* arch_unmap() might do unmaps itself. */
arch_unmap(mm, start, end);
/* Find the first overlapping VMA */
vma = vma_find(vmi, end);
if (!vma)
return 0;
return do_vmi_align_munmap(vmi, vma, mm, start, end, uf, downgrade);
}
/* do_munmap() - Wrapper function for non-maple tree aware do_munmap() calls.
* @mm: The mm_struct
* @start: The start address to munmap
* @len: The length to be munmapped.
* @uf: The userfaultfd list_head
*/
int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
struct list_head *uf)
{
VMA_ITERATOR(vmi, mm, start);
return do_vmi_munmap(&vmi, mm, start, len, uf, false);
}
unsigned long mmap_region(struct file *file, unsigned long addr,
unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
struct list_head *uf)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma = NULL;
struct vm_area_struct *next, *prev, *merge;
pgoff_t pglen = len >> PAGE_SHIFT;
unsigned long charged = 0;
unsigned long end = addr + len;
unsigned long merge_start = addr, merge_end = end;
pgoff_t vm_pgoff;
int error;
VMA_ITERATOR(vmi, mm, addr);
/* Check against address space limit. */
if (!may_expand_vm(mm, vm_flags, len >> PAGE_SHIFT)) {
unsigned long nr_pages;
/*
* MAP_FIXED may remove pages of mappings that intersects with
* requested mapping. Account for the pages it would unmap.
*/
nr_pages = count_vma_pages_range(mm, addr, end);
if (!may_expand_vm(mm, vm_flags,
(len >> PAGE_SHIFT) - nr_pages))
return -ENOMEM;
}
/* Unmap any existing mapping in the area */
if (do_vmi_munmap(&vmi, mm, addr, len, uf, false))
return -ENOMEM;
/*
* Private writable mapping: check memory availability
*/
if (accountable_mapping(file, vm_flags)) {
charged = len >> PAGE_SHIFT;
if (security_vm_enough_memory_mm(mm, charged))
return -ENOMEM;
vm_flags |= VM_ACCOUNT;
}
next = vma_next(&vmi);
prev = vma_prev(&vmi);
if (vm_flags & VM_SPECIAL)
goto cannot_expand;
/* Attempt to expand an old mapping */
/* Check next */
if (next && next->vm_start == end && !vma_policy(next) &&
can_vma_merge_before(next, vm_flags, NULL, file, pgoff+pglen,
NULL_VM_UFFD_CTX, NULL)) {
merge_end = next->vm_end;
vma = next;
vm_pgoff = next->vm_pgoff - pglen;
}
/* Check prev */
if (prev && prev->vm_end == addr && !vma_policy(prev) &&
(vma ? can_vma_merge_after(prev, vm_flags, vma->anon_vma, file,
pgoff, vma->vm_userfaultfd_ctx, NULL) :
can_vma_merge_after(prev, vm_flags, NULL, file, pgoff,
NULL_VM_UFFD_CTX, NULL))) {
merge_start = prev->vm_start;
vma = prev;
vm_pgoff = prev->vm_pgoff;
}
/* Actually expand, if possible */
if (vma &&
!vma_expand(&vmi, vma, merge_start, merge_end, vm_pgoff, next)) {
khugepaged_enter_vma(vma, vm_flags);
goto expanded;
}
cannot_expand:
if (prev)
vma_iter_next_range(&vmi);
/*
* Determine the object being mapped and call the appropriate
* specific mapper. the address has already been validated, but
* not unmapped, but the maps are removed from the list.
*/
vma = vm_area_alloc(mm);
if (!vma) {
error = -ENOMEM;
goto unacct_error;
}
vma_iter_set(&vmi, addr);
vma->vm_start = addr;
vma->vm_end = end;
vm_flags_init(vma, vm_flags);
vma->vm_page_prot = vm_get_page_prot(vm_flags);
vma->vm_pgoff = pgoff;
if (file) {
if (vm_flags & VM_SHARED) {
error = mapping_map_writable(file->f_mapping);
if (error)
goto free_vma;
}
vma->vm_file = get_file(file);
error = call_mmap(file, vma);
if (error)
goto unmap_and_free_vma;
/*
* Expansion is handled above, merging is handled below.
* Drivers should not alter the address of the VMA.
*/
error = -EINVAL;
if (WARN_ON((addr != vma->vm_start)))
goto close_and_free_vma;
vma_iter_set(&vmi, addr);
/*
* If vm_flags changed after call_mmap(), we should try merge
* vma again as we may succeed this time.
*/
if (unlikely(vm_flags != vma->vm_flags && prev)) {
merge = vma_merge(&vmi, mm, prev, vma->vm_start,
vma->vm_end, vma->vm_flags, NULL,
vma->vm_file, vma->vm_pgoff, NULL,
NULL_VM_UFFD_CTX, NULL);
if (merge) {
/*
* ->mmap() can change vma->vm_file and fput
* the original file. So fput the vma->vm_file
* here or we would add an extra fput for file
* and cause general protection fault
* ultimately.
*/
fput(vma->vm_file);
vm_area_free(vma);
vma = merge;
/* Update vm_flags to pick up the change. */
vm_flags = vma->vm_flags;
goto unmap_writable;
}
}
vm_flags = vma->vm_flags;
} else if (vm_flags & VM_SHARED) {
error = shmem_zero_setup(vma);
if (error)
goto free_vma;
} else {
vma_set_anonymous(vma);
}
if (map_deny_write_exec(vma, vma->vm_flags)) {
error = -EACCES;
goto close_and_free_vma;
}
/* Allow architectures to sanity-check the vm_flags */
error = -EINVAL;
if (!arch_validate_flags(vma->vm_flags))
goto close_and_free_vma;
error = -ENOMEM;
if (vma_iter_prealloc(&vmi))
goto close_and_free_vma;
if (vma->vm_file)
i_mmap_lock_write(vma->vm_file->f_mapping);
vma_iter_store(&vmi, vma);
mm->map_count++;
if (vma->vm_file) {
if (vma->vm_flags & VM_SHARED)
mapping_allow_writable(vma->vm_file->f_mapping);
flush_dcache_mmap_lock(vma->vm_file->f_mapping);
vma_interval_tree_insert(vma, &vma->vm_file->f_mapping->i_mmap);
flush_dcache_mmap_unlock(vma->vm_file->f_mapping);
i_mmap_unlock_write(vma->vm_file->f_mapping);
}
/*
* vma_merge() calls khugepaged_enter_vma() either, the below
* call covers the non-merge case.
*/
khugepaged_enter_vma(vma, vma->vm_flags);
/* Once vma denies write, undo our temporary denial count */
unmap_writable:
if (file && vm_flags & VM_SHARED)
mapping_unmap_writable(file->f_mapping);
file = vma->vm_file;
ksm_add_vma(vma);
expanded:
perf_event_mmap(vma);
vm_stat_account(mm, vm_flags, len >> PAGE_SHIFT);
if (vm_flags & VM_LOCKED) {
if ((vm_flags & VM_SPECIAL) || vma_is_dax(vma) ||
is_vm_hugetlb_page(vma) ||
vma == get_gate_vma(current->mm))
vm_flags_clear(vma, VM_LOCKED_MASK);
else
mm->locked_vm += (len >> PAGE_SHIFT);
}
if (file)
uprobe_mmap(vma);
/*
* New (or expanded) vma always get soft dirty status.
* Otherwise user-space soft-dirty page tracker won't
* be able to distinguish situation when vma area unmapped,
* then new mapped in-place (which must be aimed as
* a completely new data area).
*/
vm_flags_set(vma, VM_SOFTDIRTY);
vma_set_page_prot(vma);
validate_mm(mm);
return addr;
close_and_free_vma:
if (file && vma->vm_ops && vma->vm_ops->close)
vma->vm_ops->close(vma);
if (file || vma->vm_file) {
unmap_and_free_vma:
fput(vma->vm_file);
vma->vm_file = NULL;
/* Undo any partial mapping done by a device driver. */
unmap_region(mm, &mm->mm_mt, vma, prev, next, vma->vm_start,
vma->vm_end, true);
}
if (file && (vm_flags & VM_SHARED))
mapping_unmap_writable(file->f_mapping);
free_vma:
vm_area_free(vma);
unacct_error:
if (charged)
vm_unacct_memory(charged);
validate_mm(mm);
return error;
}
static int __vm_munmap(unsigned long start, size_t len, bool downgrade)
{
int ret;
struct mm_struct *mm = current->mm;
LIST_HEAD(uf);
VMA_ITERATOR(vmi, mm, start);
if (mmap_write_lock_killable(mm))
return -EINTR;
ret = do_vmi_munmap(&vmi, mm, start, len, &uf, downgrade);
/*
* Returning 1 indicates mmap_lock is downgraded.
* But 1 is not legal return value of vm_munmap() and munmap(), reset
* it to 0 before return.
*/
if (ret == 1) {
mmap_read_unlock(mm);
ret = 0;
} else
mmap_write_unlock(mm);
userfaultfd_unmap_complete(mm, &uf);
return ret;
}
int vm_munmap(unsigned long start, size_t len)
{
return __vm_munmap(start, len, false);
}
EXPORT_SYMBOL(vm_munmap);
SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
{
addr = untagged_addr(addr);
return __vm_munmap(addr, len, true);
}
/*
* Emulation of deprecated remap_file_pages() syscall.
*/
SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
unsigned long, prot, unsigned long, pgoff, unsigned long, flags)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
unsigned long populate = 0;
unsigned long ret = -EINVAL;
struct file *file;
pr_warn_once("%s (%d) uses deprecated remap_file_pages() syscall. See Documentation/mm/remap_file_pages.rst.\n",
current->comm, current->pid);
if (prot)
return ret;
start = start & PAGE_MASK;
size = size & PAGE_MASK;
if (start + size <= start)
return ret;
/* Does pgoff wrap? */
if (pgoff + (size >> PAGE_SHIFT) < pgoff)
return ret;
if (mmap_write_lock_killable(mm))
return -EINTR;
vma = vma_lookup(mm, start);
if (!vma || !(vma->vm_flags & VM_SHARED))
goto out;
if (start + size > vma->vm_end) {
VMA_ITERATOR(vmi, mm, vma->vm_end);
struct vm_area_struct *next, *prev = vma;
for_each_vma_range(vmi, next, start + size) {
/* hole between vmas ? */
if (next->vm_start != prev->vm_end)
goto out;
if (next->vm_file != vma->vm_file)
goto out;
if (next->vm_flags != vma->vm_flags)
goto out;
if (start + size <= next->vm_end)
break;
prev = next;
}
if (!next)
goto out;
}
prot |= vma->vm_flags & VM_READ ? PROT_READ : 0;
prot |= vma->vm_flags & VM_WRITE ? PROT_WRITE : 0;
prot |= vma->vm_flags & VM_EXEC ? PROT_EXEC : 0;
flags &= MAP_NONBLOCK;
flags |= MAP_SHARED | MAP_FIXED | MAP_POPULATE;
if (vma->vm_flags & VM_LOCKED)
flags |= MAP_LOCKED;
file = get_file(vma->vm_file);
ret = do_mmap(vma->vm_file, start, size,
prot, flags, pgoff, &populate, NULL);
fput(file);
out:
mmap_write_unlock(mm);
if (populate)
mm_populate(ret, populate);
if (!IS_ERR_VALUE(ret))
ret = 0;
return ret;
}
/*
* do_vma_munmap() - Unmap a full or partial vma.
* @vmi: The vma iterator pointing at the vma
* @vma: The first vma to be munmapped
* @start: the start of the address to unmap
* @end: The end of the address to unmap
* @uf: The userfaultfd list_head
* @downgrade: Attempt to downgrade or not
*
* Returns: 0 on success and not downgraded, 1 on success and downgraded.
* unmaps a VMA mapping when the vma iterator is already in position.
* Does not handle alignment.
*/
int do_vma_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
unsigned long start, unsigned long end,
struct list_head *uf, bool downgrade)
{
struct mm_struct *mm = vma->vm_mm;
int ret;
arch_unmap(mm, start, end);
ret = do_vmi_align_munmap(vmi, vma, mm, start, end, uf, downgrade);
validate_mm(mm);
return ret;
}
/*
* do_brk_flags() - Increase the brk vma if the flags match.
* @vmi: The vma iterator
* @addr: The start address
* @len: The length of the increase
* @vma: The vma,
* @flags: The VMA Flags
*
* Extend the brk VMA from addr to addr + len. If the VMA is NULL or the flags
* do not match then create a new anonymous VMA. Eventually we may be able to
* do some brk-specific accounting here.
*/
static int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *vma,
unsigned long addr, unsigned long len, unsigned long flags)
{
struct mm_struct *mm = current->mm;
struct vma_prepare vp;
validate_mm(mm);
/*
* Check against address space limits by the changed size
* Note: This happens *after* clearing old mappings in some code paths.
*/
flags |= VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
if (!may_expand_vm(mm, flags, len >> PAGE_SHIFT))
return -ENOMEM;
if (mm->map_count > sysctl_max_map_count)
return -ENOMEM;
if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT))
return -ENOMEM;
/*
* Expand the existing vma if possible; Note that singular lists do not
* occur after forking, so the expand will only happen on new VMAs.
*/
if (vma && vma->vm_end == addr && !vma_policy(vma) &&
can_vma_merge_after(vma, flags, NULL, NULL,
addr >> PAGE_SHIFT, NULL_VM_UFFD_CTX, NULL)) {
if (vma_iter_prealloc(vmi))
goto unacct_fail;
init_vma_prep(&vp, vma);
vma_prepare(&vp);
vma_adjust_trans_huge(vma, vma->vm_start, addr + len, 0);
vma->vm_end = addr + len;
vm_flags_set(vma, VM_SOFTDIRTY);
vma_iter_store(vmi, vma);
vma_complete(&vp, vmi, mm);
khugepaged_enter_vma(vma, flags);
goto out;
}
/* create a vma struct for an anonymous mapping */
vma = vm_area_alloc(mm);
if (!vma)
goto unacct_fail;
vma_set_anonymous(vma);
vma->vm_start = addr;
vma->vm_end = addr + len;
vma->vm_pgoff = addr >> PAGE_SHIFT;
vm_flags_init(vma, flags);
vma->vm_page_prot = vm_get_page_prot(flags);
if (vma_iter_store_gfp(vmi, vma, GFP_KERNEL))
goto mas_store_fail;
mm->map_count++;
ksm_add_vma(vma);
out:
perf_event_mmap(vma);
mm->total_vm += len >> PAGE_SHIFT;
mm->data_vm += len >> PAGE_SHIFT;
if (flags & VM_LOCKED)
mm->locked_vm += (len >> PAGE_SHIFT);
vm_flags_set(vma, VM_SOFTDIRTY);
validate_mm(mm);
return 0;
mas_store_fail:
vm_area_free(vma);
unacct_fail:
vm_unacct_memory(len >> PAGE_SHIFT);
return -ENOMEM;
}
int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma = NULL;
unsigned long len;
int ret;
bool populate;
LIST_HEAD(uf);
VMA_ITERATOR(vmi, mm, addr);
len = PAGE_ALIGN(request);
if (len < request)
return -ENOMEM;
if (!len)
return 0;
if (mmap_write_lock_killable(mm))
return -EINTR;
/* Until we need other flags, refuse anything except VM_EXEC. */
if ((flags & (~VM_EXEC)) != 0)
return -EINVAL;
ret = check_brk_limits(addr, len);
if (ret)
goto limits_failed;
ret = do_vmi_munmap(&vmi, mm, addr, len, &uf, 0);
if (ret)
goto munmap_failed;
vma = vma_prev(&vmi);
ret = do_brk_flags(&vmi, vma, addr, len, flags);
populate = ((mm->def_flags & VM_LOCKED) != 0);
mmap_write_unlock(mm);
userfaultfd_unmap_complete(mm, &uf);
if (populate && !ret)
mm_populate(addr, len);
return ret;
munmap_failed:
limits_failed:
mmap_write_unlock(mm);
return ret;
}
EXPORT_SYMBOL(vm_brk_flags);
int vm_brk(unsigned long addr, unsigned long len)
{
return vm_brk_flags(addr, len, 0);
}
EXPORT_SYMBOL(vm_brk);
/* Release all mmaps. */
void exit_mmap(struct mm_struct *mm)
{
struct mmu_gather tlb;
struct vm_area_struct *vma;
unsigned long nr_accounted = 0;
MA_STATE(mas, &mm->mm_mt, 0, 0);
int count = 0;
/* mm's last user has gone, and its about to be pulled down */
mmu_notifier_release(mm);
mmap_read_lock(mm);
arch_exit_mmap(mm);
vma = mas_find(&mas, ULONG_MAX);
if (!vma) {
/* Can happen if dup_mmap() received an OOM */
mmap_read_unlock(mm);
return;
}
lru_add_drain();
flush_cache_mm(mm);
tlb_gather_mmu_fullmm(&tlb, mm);
/* update_hiwater_rss(mm) here? but nobody should be looking */
/* Use ULONG_MAX here to ensure all VMAs in the mm are unmapped */
unmap_vmas(&tlb, &mm->mm_mt, vma, 0, ULONG_MAX, false);
mmap_read_unlock(mm);
/*
* Set MMF_OOM_SKIP to hide this task from the oom killer/reaper
* because the memory has been already freed.
*/
set_bit(MMF_OOM_SKIP, &mm->flags);
mmap_write_lock(mm);
mt_clear_in_rcu(&mm->mm_mt);
free_pgtables(&tlb, &mm->mm_mt, vma, FIRST_USER_ADDRESS,
USER_PGTABLES_CEILING, true);
tlb_finish_mmu(&tlb);
/*
* Walk the list again, actually closing and freeing it, with preemption
* enabled, without holding any MM locks besides the unreachable
* mmap_write_lock.
*/
do {
if (vma->vm_flags & VM_ACCOUNT)
nr_accounted += vma_pages(vma);
remove_vma(vma, true);
count++;
cond_resched();
} while ((vma = mas_find(&mas, ULONG_MAX)) != NULL);
BUG_ON(count != mm->map_count);
trace_exit_mmap(mm);
__mt_destroy(&mm->mm_mt);
mmap_write_unlock(mm);
vm_unacct_memory(nr_accounted);
}
/* Insert vm structure into process list sorted by address
* and into the inode's i_mmap tree. If vm_file is non-NULL
* then i_mmap_rwsem is taken here.
*/
int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
{
unsigned long charged = vma_pages(vma);
if (find_vma_intersection(mm, vma->vm_start, vma->vm_end))
return -ENOMEM;
if ((vma->vm_flags & VM_ACCOUNT) &&
security_vm_enough_memory_mm(mm, charged))
return -ENOMEM;
/*
* The vm_pgoff of a purely anonymous vma should be irrelevant
* until its first write fault, when page's anon_vma and index
* are set. But now set the vm_pgoff it will almost certainly
* end up with (unless mremap moves it elsewhere before that
* first wfault), so /proc/pid/maps tells a consistent story.
*
* By setting it to reflect the virtual start address of the
* vma, merges and splits can happen in a seamless way, just
* using the existing file pgoff checks and manipulations.
* Similarly in do_mmap and in do_brk_flags.
*/
if (vma_is_anonymous(vma)) {
BUG_ON(vma->anon_vma);
vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
}
if (vma_link(mm, vma)) {
vm_unacct_memory(charged);
return -ENOMEM;
}
return 0;
}
/*
* Copy the vma structure to a new location in the same mm,
* prior to moving page table entries, to effect an mremap move.
*/
struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
unsigned long addr, unsigned long len, pgoff_t pgoff,
bool *need_rmap_locks)
{
struct vm_area_struct *vma = *vmap;
unsigned long vma_start = vma->vm_start;
struct mm_struct *mm = vma->vm_mm;
struct vm_area_struct *new_vma, *prev;
bool faulted_in_anon_vma = true;
VMA_ITERATOR(vmi, mm, addr);
validate_mm(mm);
/*
* If anonymous vma has not yet been faulted, update new pgoff
* to match new location, to increase its chance of merging.
*/
if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma)) {
pgoff = addr >> PAGE_SHIFT;
faulted_in_anon_vma = false;
}
new_vma = find_vma_prev(mm, addr, &prev);
if (new_vma && new_vma->vm_start < addr + len)
return NULL; /* should never get here */
new_vma = vma_merge(&vmi, mm, prev, addr, addr + len, vma->vm_flags,
vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
vma->vm_userfaultfd_ctx, anon_vma_name(vma));
if (new_vma) {
/*
* Source vma may have been merged into new_vma
*/
if (unlikely(vma_start >= new_vma->vm_start &&
vma_start < new_vma->vm_end)) {
/*
* The only way we can get a vma_merge with
* self during an mremap is if the vma hasn't
* been faulted in yet and we were allowed to
* reset the dst vma->vm_pgoff to the
* destination address of the mremap to allow
* the merge to happen. mremap must change the
* vm_pgoff linearity between src and dst vmas
* (in turn preventing a vma_merge) to be
* safe. It is only safe to keep the vm_pgoff
* linear if there are no pages mapped yet.
*/
VM_BUG_ON_VMA(faulted_in_anon_vma, new_vma);
*vmap = vma = new_vma;
}
*need_rmap_locks = (new_vma->vm_pgoff <= vma->vm_pgoff);
} else {
new_vma = vm_area_dup(vma);
if (!new_vma)
goto out;
new_vma->vm_start = addr;
new_vma->vm_end = addr + len;
new_vma->vm_pgoff = pgoff;
if (vma_dup_policy(vma, new_vma))
goto out_free_vma;
if (anon_vma_clone(new_vma, vma))
goto out_free_mempol;
if (new_vma->vm_file)
get_file(new_vma->vm_file);
if (new_vma->vm_ops && new_vma->vm_ops->open)
new_vma->vm_ops->open(new_vma);
vma_start_write(new_vma);
if (vma_link(mm, new_vma))
goto out_vma_link;
*need_rmap_locks = false;
}
validate_mm(mm);
return new_vma;
out_vma_link:
if (new_vma->vm_ops && new_vma->vm_ops->close)
new_vma->vm_ops->close(new_vma);
if (new_vma->vm_file)
fput(new_vma->vm_file);
unlink_anon_vmas(new_vma);
out_free_mempol:
mpol_put(vma_policy(new_vma));
out_free_vma:
vm_area_free(new_vma);
out:
validate_mm(mm);
return NULL;
}
/*
* Return true if the calling process may expand its vm space by the passed
* number of pages
*/
bool may_expand_vm(struct mm_struct *mm, vm_flags_t flags, unsigned long npages)
{
if (mm->total_vm + npages > rlimit(RLIMIT_AS) >> PAGE_SHIFT)
return false;
if (is_data_mapping(flags) &&
mm->data_vm + npages > rlimit(RLIMIT_DATA) >> PAGE_SHIFT) {
/* Workaround for Valgrind */
if (rlimit(RLIMIT_DATA) == 0 &&
mm->data_vm + npages <= rlimit_max(RLIMIT_DATA) >> PAGE_SHIFT)
return true;
pr_warn_once("%s (%d): VmData %lu exceed data ulimit %lu. Update limits%s.\n",
current->comm, current->pid,
(mm->data_vm + npages) << PAGE_SHIFT,
rlimit(RLIMIT_DATA),
ignore_rlimit_data ? "" : " or use boot option ignore_rlimit_data");
if (!ignore_rlimit_data)
return false;
}
return true;
}
void vm_stat_account(struct mm_struct *mm, vm_flags_t flags, long npages)
{
WRITE_ONCE(mm->total_vm, READ_ONCE(mm->total_vm)+npages);
if (is_exec_mapping(flags))
mm->exec_vm += npages;
else if (is_stack_mapping(flags))
mm->stack_vm += npages;
else if (is_data_mapping(flags))
mm->data_vm += npages;
}
static vm_fault_t special_mapping_fault(struct vm_fault *vmf);
/*
* Having a close hook prevents vma merging regardless of flags.
*/
static void special_mapping_close(struct vm_area_struct *vma)
{
}
static const char *special_mapping_name(struct vm_area_struct *vma)
{
return ((struct vm_special_mapping *)vma->vm_private_data)->name;
}
static int special_mapping_mremap(struct vm_area_struct *new_vma)
{
struct vm_special_mapping *sm = new_vma->vm_private_data;
if (WARN_ON_ONCE(current->mm != new_vma->vm_mm))
return -EFAULT;
if (sm->mremap)
return sm->mremap(sm, new_vma);
return 0;
}
static int special_mapping_split(struct vm_area_struct *vma, unsigned long addr)
{
/*
* Forbid splitting special mappings - kernel has expectations over
* the number of pages in mapping. Together with VM_DONTEXPAND
* the size of vma should stay the same over the special mapping's
* lifetime.
*/
return -EINVAL;
}
static const struct vm_operations_struct special_mapping_vmops = {
.close = special_mapping_close,
.fault = special_mapping_fault,
.mremap = special_mapping_mremap,
.name = special_mapping_name,
/* vDSO code relies that VVAR can't be accessed remotely */
.access = NULL,
.may_split = special_mapping_split,
};
static const struct vm_operations_struct legacy_special_mapping_vmops = {
.close = special_mapping_close,
.fault = special_mapping_fault,
};
static vm_fault_t special_mapping_fault(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
pgoff_t pgoff;
struct page **pages;
if (vma->vm_ops == &legacy_special_mapping_vmops) {
pages = vma->vm_private_data;
} else {
struct vm_special_mapping *sm = vma->vm_private_data;
if (sm->fault)
return sm->fault(sm, vmf->vma, vmf);
pages = sm->pages;
}
for (pgoff = vmf->pgoff; pgoff && *pages; ++pages)
pgoff--;
if (*pages) {
struct page *page = *pages;
get_page(page);
vmf->page = page;
return 0;
}
return VM_FAULT_SIGBUS;
}
static struct vm_area_struct *__install_special_mapping(
struct mm_struct *mm,
unsigned long addr, unsigned long len,
unsigned long vm_flags, void *priv,
const struct vm_operations_struct *ops)
{
int ret;
struct vm_area_struct *vma;
validate_mm(mm);
vma = vm_area_alloc(mm);
if (unlikely(vma == NULL))
return ERR_PTR(-ENOMEM);
vma->vm_start = addr;
vma->vm_end = addr + len;
vm_flags_init(vma, (vm_flags | mm->def_flags |
VM_DONTEXPAND | VM_SOFTDIRTY) & ~VM_LOCKED_MASK);
vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
vma->vm_ops = ops;
vma->vm_private_data = priv;
ret = insert_vm_struct(mm, vma);
if (ret)
goto out;
vm_stat_account(mm, vma->vm_flags, len >> PAGE_SHIFT);
perf_event_mmap(vma);
validate_mm(mm);
return vma;
out:
vm_area_free(vma);
validate_mm(mm);
return ERR_PTR(ret);
}
bool vma_is_special_mapping(const struct vm_area_struct *vma,
const struct vm_special_mapping *sm)
{
return vma->vm_private_data == sm &&
(vma->vm_ops == &special_mapping_vmops ||
vma->vm_ops == &legacy_special_mapping_vmops);
}
/*
* Called with mm->mmap_lock held for writing.
* Insert a new vma covering the given region, with the given flags.
* Its pages are supplied by the given array of struct page *.
* The array can be shorter than len >> PAGE_SHIFT if it's null-terminated.
* The region past the last page supplied will always produce SIGBUS.
* The array pointer and the pages it points to are assumed to stay alive
* for as long as this mapping might exist.
*/
struct vm_area_struct *_install_special_mapping(
struct mm_struct *mm,
unsigned long addr, unsigned long len,
unsigned long vm_flags, const struct vm_special_mapping *spec)
{
return __install_special_mapping(mm, addr, len, vm_flags, (void *)spec,
&special_mapping_vmops);
}
int install_special_mapping(struct mm_struct *mm,
unsigned long addr, unsigned long len,
unsigned long vm_flags, struct page **pages)
{
struct vm_area_struct *vma = __install_special_mapping(
mm, addr, len, vm_flags, (void *)pages,
&legacy_special_mapping_vmops);
return PTR_ERR_OR_ZERO(vma);
}
static DEFINE_MUTEX(mm_all_locks_mutex);
static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma)
{
if (!test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_root.rb_node)) {
/*
* The LSB of head.next can't change from under us
* because we hold the mm_all_locks_mutex.
*/
down_write_nest_lock(&anon_vma->root->rwsem, &mm->mmap_lock);
/*
* We can safely modify head.next after taking the
* anon_vma->root->rwsem. If some other vma in this mm shares
* the same anon_vma we won't take it again.
*
* No need of atomic instructions here, head.next
* can't change from under us thanks to the
* anon_vma->root->rwsem.
*/
if (__test_and_set_bit(0, (unsigned long *)
&anon_vma->root->rb_root.rb_root.rb_node))
BUG();
}
}
static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
{
if (!test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
/*
* AS_MM_ALL_LOCKS can't change from under us because
* we hold the mm_all_locks_mutex.
*
* Operations on ->flags have to be atomic because
* even if AS_MM_ALL_LOCKS is stable thanks to the
* mm_all_locks_mutex, there may be other cpus
* changing other bitflags in parallel to us.
*/
if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags))
BUG();
down_write_nest_lock(&mapping->i_mmap_rwsem, &mm->mmap_lock);
}
}
/*
* This operation locks against the VM for all pte/vma/mm related
* operations that could ever happen on a certain mm. This includes
* vmtruncate, try_to_unmap, and all page faults.
*
* The caller must take the mmap_lock in write mode before calling
* mm_take_all_locks(). The caller isn't allowed to release the
* mmap_lock until mm_drop_all_locks() returns.
*
* mmap_lock in write mode is required in order to block all operations
* that could modify pagetables and free pages without need of
* altering the vma layout. It's also needed in write mode to avoid new
* anon_vmas to be associated with existing vmas.
*
* A single task can't take more than one mm_take_all_locks() in a row
* or it would deadlock.
*
* The LSB in anon_vma->rb_root.rb_node and the AS_MM_ALL_LOCKS bitflag in
* mapping->flags avoid to take the same lock twice, if more than one
* vma in this mm is backed by the same anon_vma or address_space.
*
* We take locks in following order, accordingly to comment at beginning
* of mm/rmap.c:
* - all hugetlbfs_i_mmap_rwsem_key locks (aka mapping->i_mmap_rwsem for
* hugetlb mapping);
* - all vmas marked locked
* - all i_mmap_rwsem locks;
* - all anon_vma->rwseml
*
* We can take all locks within these types randomly because the VM code
* doesn't nest them and we protected from parallel mm_take_all_locks() by
* mm_all_locks_mutex.
*
* mm_take_all_locks() and mm_drop_all_locks are expensive operations
* that may have to take thousand of locks.
*
* mm_take_all_locks() can fail if it's interrupted by signals.
*/
int mm_take_all_locks(struct mm_struct *mm)
{
struct vm_area_struct *vma;
struct anon_vma_chain *avc;
MA_STATE(mas, &mm->mm_mt, 0, 0);
mmap_assert_write_locked(mm);
mutex_lock(&mm_all_locks_mutex);
mas_for_each(&mas, vma, ULONG_MAX) {
if (signal_pending(current))
goto out_unlock;
vma_start_write(vma);
}
mas_set(&mas, 0);
mas_for_each(&mas, vma, ULONG_MAX) {
if (signal_pending(current))
goto out_unlock;
if (vma->vm_file && vma->vm_file->f_mapping &&
is_vm_hugetlb_page(vma))
vm_lock_mapping(mm, vma->vm_file->f_mapping);
}
mas_set(&mas, 0);
mas_for_each(&mas, vma, ULONG_MAX) {
if (signal_pending(current))
goto out_unlock;
if (vma->vm_file && vma->vm_file->f_mapping &&
!is_vm_hugetlb_page(vma))
vm_lock_mapping(mm, vma->vm_file->f_mapping);
}
mas_set(&mas, 0);
mas_for_each(&mas, vma, ULONG_MAX) {
if (signal_pending(current))
goto out_unlock;
if (vma->anon_vma)
list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
vm_lock_anon_vma(mm, avc->anon_vma);
}
return 0;
out_unlock:
mm_drop_all_locks(mm);
return -EINTR;
}
static void vm_unlock_anon_vma(struct anon_vma *anon_vma)
{
if (test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_root.rb_node)) {
/*
* The LSB of head.next can't change to 0 from under
* us because we hold the mm_all_locks_mutex.
*
* We must however clear the bitflag before unlocking
* the vma so the users using the anon_vma->rb_root will
* never see our bitflag.
*
* No need of atomic instructions here, head.next
* can't change from under us until we release the
* anon_vma->root->rwsem.
*/
if (!__test_and_clear_bit(0, (unsigned long *)
&anon_vma->root->rb_root.rb_root.rb_node))
BUG();
anon_vma_unlock_write(anon_vma);
}
}
static void vm_unlock_mapping(struct address_space *mapping)
{
if (test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
/*
* AS_MM_ALL_LOCKS can't change to 0 from under us
* because we hold the mm_all_locks_mutex.
*/
i_mmap_unlock_write(mapping);
if (!test_and_clear_bit(AS_MM_ALL_LOCKS,
&mapping->flags))
BUG();
}
}
/*
* The mmap_lock cannot be released by the caller until
* mm_drop_all_locks() returns.
*/
void mm_drop_all_locks(struct mm_struct *mm)
{
struct vm_area_struct *vma;
struct anon_vma_chain *avc;
MA_STATE(mas, &mm->mm_mt, 0, 0);
mmap_assert_write_locked(mm);
BUG_ON(!mutex_is_locked(&mm_all_locks_mutex));
mas_for_each(&mas, vma, ULONG_MAX) {
if (vma->anon_vma)
list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
vm_unlock_anon_vma(avc->anon_vma);
if (vma->vm_file && vma->vm_file->f_mapping)
vm_unlock_mapping(vma->vm_file->f_mapping);
}
vma_end_write_all(mm);
mutex_unlock(&mm_all_locks_mutex);
}
/*
* initialise the percpu counter for VM
*/
void __init mmap_init(void)
{
int ret;
ret = percpu_counter_init(&vm_committed_as, 0, GFP_KERNEL);
VM_BUG_ON(ret);
}
/*
* Initialise sysctl_user_reserve_kbytes.
*
* This is intended to prevent a user from starting a single memory hogging
* process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER
* mode.
*
* The default value is min(3% of free memory, 128MB)
* 128MB is enough to recover with sshd/login, bash, and top/kill.
*/
static int init_user_reserve(void)
{
unsigned long free_kbytes;
free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17);
return 0;
}
subsys_initcall(init_user_reserve);
/*
* Initialise sysctl_admin_reserve_kbytes.
*
* The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
* to log in and kill a memory hogging process.
*
* Systems with more than 256MB will reserve 8MB, enough to recover
* with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
* only reserve 3% of free pages by default.
*/
static int init_admin_reserve(void)
{
unsigned long free_kbytes;
free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
return 0;
}
subsys_initcall(init_admin_reserve);
/*
* Reinititalise user and admin reserves if memory is added or removed.
*
* The default user reserve max is 128MB, and the default max for the
* admin reserve is 8MB. These are usually, but not always, enough to
* enable recovery from a memory hogging process using login/sshd, a shell,
* and tools like top. It may make sense to increase or even disable the
* reserve depending on the existence of swap or variations in the recovery
* tools. So, the admin may have changed them.
*
* If memory is added and the reserves have been eliminated or increased above
* the default max, then we'll trust the admin.
*
* If memory is removed and there isn't enough free memory, then we
* need to reset the reserves.
*
* Otherwise keep the reserve set by the admin.
*/
static int reserve_mem_notifier(struct notifier_block *nb,
unsigned long action, void *data)
{
unsigned long tmp, free_kbytes;
switch (action) {
case MEM_ONLINE:
/* Default max is 128MB. Leave alone if modified by operator. */
tmp = sysctl_user_reserve_kbytes;
if (0 < tmp && tmp < (1UL << 17))
init_user_reserve();
/* Default max is 8MB. Leave alone if modified by operator. */
tmp = sysctl_admin_reserve_kbytes;
if (0 < tmp && tmp < (1UL << 13))
init_admin_reserve();
break;
case MEM_OFFLINE:
free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
if (sysctl_user_reserve_kbytes > free_kbytes) {
init_user_reserve();
pr_info("vm.user_reserve_kbytes reset to %lu\n",
sysctl_user_reserve_kbytes);
}
if (sysctl_admin_reserve_kbytes > free_kbytes) {
init_admin_reserve();
pr_info("vm.admin_reserve_kbytes reset to %lu\n",
sysctl_admin_reserve_kbytes);
}
break;
default:
break;
}
return NOTIFY_OK;
}
static int __meminit init_reserve_notifier(void)
{
if (hotplug_memory_notifier(reserve_mem_notifier, DEFAULT_CALLBACK_PRI))
pr_err("Failed registering memory add/remove notifier for admin reserve\n");
return 0;
}
subsys_initcall(init_reserve_notifier);
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