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mm: refactor map_deny_write_exec()

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Refactor the map_deny_write_exec() to not unnecessarily require a VMA
parameter but rather to accept VMA flags parameters, which allows us to
use this function early in mmap_region() in a subsequent commit.

While we're here, we refactor the function to be more readable and add
some additional documentation.

Link: https://lkml.kernel.org/r/6be8bb59cd7c68006ebb006eb9d8dc27104b1f70.1730224667.git.lorenzo.stoakes@oracle.com
Fixes: deb0f65628 ("mm/mmap: undo ->mmap() when arch_validate_flags() fails")
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reported-by: Jann Horn <jannh@google.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Jann Horn <jannh@google.com>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Helge Deller <deller@gmx.de>
Cc: James E.J. Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Will Deacon <will@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Lorenzo Stoakes 2024-10-29 18:11:46 +00:00 committed by Andrew Morton
parent 4080ef1579
commit 0fb4a7ad27
4 changed files with 21 additions and 6 deletions
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21
include/linux/mman.h
View File

@ -188,16 +188,31 @@ static inline bool arch_memory_deny_write_exec_supported(void)
* *
* d) mmap(PROT_READ | PROT_EXEC) * d) mmap(PROT_READ | PROT_EXEC)
* mmap(PROT_READ | PROT_EXEC | PROT_BTI) * mmap(PROT_READ | PROT_EXEC | PROT_BTI)
*
* This is only applicable if the user has set the Memory-Deny-Write-Execute
* (MDWE) protection mask for the current process.
*
* @old specifies the VMA flags the VMA originally possessed, and @new the ones
* we propose to set.
*
* Return: false if proposed change is OK, true if not ok and should be denied.
*/ */
static inline bool map_deny_write_exec(struct vm_area_struct *vma, unsigned long vm_flags) static inline bool map_deny_write_exec(unsigned long old, unsigned long new)
{ {
/* If MDWE is disabled, we have nothing to deny. */
if (!test_bit(MMF_HAS_MDWE, &current->mm->flags)) if (!test_bit(MMF_HAS_MDWE, &current->mm->flags))
return false; return false;
if ((vm_flags & VM_EXEC) && (vm_flags & VM_WRITE)) /* If the new VMA is not executable, we have nothing to deny. */
if (!(new & VM_EXEC))
return false;
/* Under MDWE we do not accept newly writably executable VMAs... */
if (new & VM_WRITE)
return true; return true;
if (!(vma->vm_flags & VM_EXEC) && (vm_flags & VM_EXEC)) /* ...nor previously non-executable VMAs becoming executable. */
if (!(old & VM_EXEC))
return true; return true;
return false; return false;

2
mm/mmap.c
View File

@ -1505,7 +1505,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
vma_set_anonymous(vma); vma_set_anonymous(vma);
} }
if (map_deny_write_exec(vma, vma->vm_flags)) { if (map_deny_write_exec(vma->vm_flags, vma->vm_flags)) {
error = -EACCES; error = -EACCES;
goto close_and_free_vma; goto close_and_free_vma;
} }

2
mm/mprotect.c
View File

@ -810,7 +810,7 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
break; break;
} }
if (map_deny_write_exec(vma, newflags)) { if (map_deny_write_exec(vma->vm_flags, newflags)) {
error = -EACCES; error = -EACCES;
break; break;
} }

2
mm/vma.h
View File

@ -42,7 +42,7 @@ struct vma_munmap_struct {
int vma_count; /* Number of vmas that will be removed */ int vma_count; /* Number of vmas that will be removed */
bool unlock; /* Unlock after the munmap */ bool unlock; /* Unlock after the munmap */
bool clear_ptes; /* If there are outstanding PTE to be cleared */ bool clear_ptes; /* If there are outstanding PTE to be cleared */
/* 1 byte hole */ /* 2 byte hole */
unsigned long nr_pages; /* Number of pages being removed */ unsigned long nr_pages; /* Number of pages being removed */
unsigned long locked_vm; /* Number of locked pages */ unsigned long locked_vm; /* Number of locked pages */
unsigned long nr_accounted; /* Number of VM_ACCOUNT pages */ unsigned long nr_accounted; /* Number of VM_ACCOUNT pages */