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linux/fs/ext4/acl.c
Satyam Sharma 3bd858ab1c Introduce is_owner_or_cap() to wrap CAP_FOWNER use with fsuid check 
Introduce is_owner_or_cap() macro in fs.h, and convert over relevant
users to it. This is done because we want to avoid bugs in the future
where we check for only effective fsuid of the current task against a
file's owning uid, without simultaneously checking for CAP_FOWNER as
well, thus violating its semantics.
[ XFS uses special macros and structures, and in general looked ...
untouchable, so we leave it alone -- but it has been looked over. ]

The (current->fsuid != inode->i_uid) check in generic_permission() and
exec_permission_lite() is left alone, because those operations are
covered by CAP_DAC_OVERRIDE and CAP_DAC_READ_SEARCH. Similarly operations
falling under the purview of CAP_CHOWN and CAP_LEASE are also left alone.

Signed-off-by: Satyam Sharma <ssatyam@cse.iitk.ac.in>
Cc: Al Viro <viro@ftp.linux.org.uk>
Acked-by: Serge E. Hallyn <serge@hallyn.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-17 12:00:03 -07:00

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/*
* linux/fs/ext4/acl.c
*
* Copyright (C) 2001-2003 Andreas Gruenbacher, <agruen@suse.de>
*/
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/capability.h>
#include <linux/fs.h>
#include <linux/ext4_jbd2.h>
#include <linux/ext4_fs.h>
#include "xattr.h"
#include "acl.h"
/*
* Convert from filesystem to in-memory representation.
*/
static struct posix_acl *
ext4_acl_from_disk(const void *value, size_t size)
{
const char *end = (char *)value + size;
int n, count;
struct posix_acl *acl;
if (!value)
return NULL;
if (size < sizeof(ext4_acl_header))
return ERR_PTR(-EINVAL);
if (((ext4_acl_header *)value)->a_version !=
cpu_to_le32(EXT4_ACL_VERSION))
return ERR_PTR(-EINVAL);
value = (char *)value + sizeof(ext4_acl_header);
count = ext4_acl_count(size);
if (count < 0)
return ERR_PTR(-EINVAL);
if (count == 0)
return NULL;
acl = posix_acl_alloc(count, GFP_KERNEL);
if (!acl)
return ERR_PTR(-ENOMEM);
for (n=0; n < count; n++) {
ext4_acl_entry *entry =
(ext4_acl_entry *)value;
if ((char *)value + sizeof(ext4_acl_entry_short) > end)
goto fail;
acl->a_entries[n].e_tag = le16_to_cpu(entry->e_tag);
acl->a_entries[n].e_perm = le16_to_cpu(entry->e_perm);
switch(acl->a_entries[n].e_tag) {
case ACL_USER_OBJ:
case ACL_GROUP_OBJ:
case ACL_MASK:
case ACL_OTHER:
value = (char *)value +
sizeof(ext4_acl_entry_short);
acl->a_entries[n].e_id = ACL_UNDEFINED_ID;
break;
case ACL_USER:
case ACL_GROUP:
value = (char *)value + sizeof(ext4_acl_entry);
if ((char *)value > end)
goto fail;
acl->a_entries[n].e_id =
le32_to_cpu(entry->e_id);
break;
default:
goto fail;
}
}
if (value != end)
goto fail;
return acl;
fail:
posix_acl_release(acl);
return ERR_PTR(-EINVAL);
}
/*
* Convert from in-memory to filesystem representation.
*/
static void *
ext4_acl_to_disk(const struct posix_acl *acl, size_t *size)
{
ext4_acl_header *ext_acl;
char *e;
size_t n;
*size = ext4_acl_size(acl->a_count);
ext_acl = kmalloc(sizeof(ext4_acl_header) + acl->a_count *
sizeof(ext4_acl_entry), GFP_KERNEL);
if (!ext_acl)
return ERR_PTR(-ENOMEM);
ext_acl->a_version = cpu_to_le32(EXT4_ACL_VERSION);
e = (char *)ext_acl + sizeof(ext4_acl_header);
for (n=0; n < acl->a_count; n++) {
ext4_acl_entry *entry = (ext4_acl_entry *)e;
entry->e_tag = cpu_to_le16(acl->a_entries[n].e_tag);
entry->e_perm = cpu_to_le16(acl->a_entries[n].e_perm);
switch(acl->a_entries[n].e_tag) {
case ACL_USER:
case ACL_GROUP:
entry->e_id =
cpu_to_le32(acl->a_entries[n].e_id);
e += sizeof(ext4_acl_entry);
break;
case ACL_USER_OBJ:
case ACL_GROUP_OBJ:
case ACL_MASK:
case ACL_OTHER:
e += sizeof(ext4_acl_entry_short);
break;
default:
goto fail;
}
}
return (char *)ext_acl;
fail:
kfree(ext_acl);
return ERR_PTR(-EINVAL);
}
static inline struct posix_acl *
ext4_iget_acl(struct inode *inode, struct posix_acl **i_acl)
{
struct posix_acl *acl = EXT4_ACL_NOT_CACHED;
spin_lock(&inode->i_lock);
if (*i_acl != EXT4_ACL_NOT_CACHED)
acl = posix_acl_dup(*i_acl);
spin_unlock(&inode->i_lock);
return acl;
}
static inline void
ext4_iset_acl(struct inode *inode, struct posix_acl **i_acl,
struct posix_acl *acl)
{
spin_lock(&inode->i_lock);
if (*i_acl != EXT4_ACL_NOT_CACHED)
posix_acl_release(*i_acl);
*i_acl = posix_acl_dup(acl);
spin_unlock(&inode->i_lock);
}
/*
* Inode operation get_posix_acl().
*
* inode->i_mutex: don't care
*/
static struct posix_acl *
ext4_get_acl(struct inode *inode, int type)
{
struct ext4_inode_info *ei = EXT4_I(inode);
int name_index;
char *value = NULL;
struct posix_acl *acl;
int retval;
if (!test_opt(inode->i_sb, POSIX_ACL))
return NULL;
switch(type) {
case ACL_TYPE_ACCESS:
acl = ext4_iget_acl(inode, &ei->i_acl);
if (acl != EXT4_ACL_NOT_CACHED)
return acl;
name_index = EXT4_XATTR_INDEX_POSIX_ACL_ACCESS;
break;
case ACL_TYPE_DEFAULT:
acl = ext4_iget_acl(inode, &ei->i_default_acl);
if (acl != EXT4_ACL_NOT_CACHED)
return acl;
name_index = EXT4_XATTR_INDEX_POSIX_ACL_DEFAULT;
break;
default:
return ERR_PTR(-EINVAL);
}
retval = ext4_xattr_get(inode, name_index, "", NULL, 0);
if (retval > 0) {
value = kmalloc(retval, GFP_KERNEL);
if (!value)
return ERR_PTR(-ENOMEM);
retval = ext4_xattr_get(inode, name_index, "", value, retval);
}
if (retval > 0)
acl = ext4_acl_from_disk(value, retval);
else if (retval == -ENODATA || retval == -ENOSYS)
acl = NULL;
else
acl = ERR_PTR(retval);
kfree(value);
if (!IS_ERR(acl)) {
switch(type) {
case ACL_TYPE_ACCESS:
ext4_iset_acl(inode, &ei->i_acl, acl);
break;
case ACL_TYPE_DEFAULT:
ext4_iset_acl(inode, &ei->i_default_acl, acl);
break;
}
}
return acl;
}
/*
* Set the access or default ACL of an inode.
*
* inode->i_mutex: down unless called from ext4_new_inode
*/
static int
ext4_set_acl(handle_t *handle, struct inode *inode, int type,
struct posix_acl *acl)
{
struct ext4_inode_info *ei = EXT4_I(inode);
int name_index;
void *value = NULL;
size_t size = 0;
int error;
if (S_ISLNK(inode->i_mode))
return -EOPNOTSUPP;
switch(type) {
case ACL_TYPE_ACCESS:
name_index = EXT4_XATTR_INDEX_POSIX_ACL_ACCESS;
if (acl) {
mode_t mode = inode->i_mode;
error = posix_acl_equiv_mode(acl, &mode);
if (error < 0)
return error;
else {
inode->i_mode = mode;
ext4_mark_inode_dirty(handle, inode);
if (error == 0)
acl = NULL;
}
}
break;
case ACL_TYPE_DEFAULT:
name_index = EXT4_XATTR_INDEX_POSIX_ACL_DEFAULT;
if (!S_ISDIR(inode->i_mode))
return acl ? -EACCES : 0;
break;
default:
return -EINVAL;
}
if (acl) {
value = ext4_acl_to_disk(acl, &size);
if (IS_ERR(value))
return (int)PTR_ERR(value);
}
error = ext4_xattr_set_handle(handle, inode, name_index, "",
value, size, 0);
kfree(value);
if (!error) {
switch(type) {
case ACL_TYPE_ACCESS:
ext4_iset_acl(inode, &ei->i_acl, acl);
break;
case ACL_TYPE_DEFAULT:
ext4_iset_acl(inode, &ei->i_default_acl, acl);
break;
}
}
return error;
}
static int
ext4_check_acl(struct inode *inode, int mask)
{
struct posix_acl *acl = ext4_get_acl(inode, ACL_TYPE_ACCESS);
if (IS_ERR(acl))
return PTR_ERR(acl);
if (acl) {
int error = posix_acl_permission(inode, acl, mask);
posix_acl_release(acl);
return error;
}
return -EAGAIN;
}
int
ext4_permission(struct inode *inode, int mask, struct nameidata *nd)
{
return generic_permission(inode, mask, ext4_check_acl);
}
/*
* Initialize the ACLs of a new inode. Called from ext4_new_inode.
*
* dir->i_mutex: down
* inode->i_mutex: up (access to inode is still exclusive)
*/
int
ext4_init_acl(handle_t *handle, struct inode *inode, struct inode *dir)
{
struct posix_acl *acl = NULL;
int error = 0;
if (!S_ISLNK(inode->i_mode)) {
if (test_opt(dir->i_sb, POSIX_ACL)) {
acl = ext4_get_acl(dir, ACL_TYPE_DEFAULT);
if (IS_ERR(acl))
return PTR_ERR(acl);
}
if (!acl)
inode->i_mode &= ~current->fs->umask;
}
if (test_opt(inode->i_sb, POSIX_ACL) && acl) {
struct posix_acl *clone;
mode_t mode;
if (S_ISDIR(inode->i_mode)) {
error = ext4_set_acl(handle, inode,
ACL_TYPE_DEFAULT, acl);
if (error)
goto cleanup;
}
clone = posix_acl_clone(acl, GFP_KERNEL);
error = -ENOMEM;
if (!clone)
goto cleanup;
mode = inode->i_mode;
error = posix_acl_create_masq(clone, &mode);
if (error >= 0) {
inode->i_mode = mode;
if (error > 0) {
/* This is an extended ACL */
error = ext4_set_acl(handle, inode,
ACL_TYPE_ACCESS, clone);
}
}
posix_acl_release(clone);
}
cleanup:
posix_acl_release(acl);
return error;
}
/*
* Does chmod for an inode that may have an Access Control List. The
* inode->i_mode field must be updated to the desired value by the caller
* before calling this function.
* Returns 0 on success, or a negative error number.
*
* We change the ACL rather than storing some ACL entries in the file
* mode permission bits (which would be more efficient), because that
* would break once additional permissions (like ACL_APPEND, ACL_DELETE
* for directories) are added. There are no more bits available in the
* file mode.
*
* inode->i_mutex: down
*/
int
ext4_acl_chmod(struct inode *inode)
{
struct posix_acl *acl, *clone;
int error;
if (S_ISLNK(inode->i_mode))
return -EOPNOTSUPP;
if (!test_opt(inode->i_sb, POSIX_ACL))
return 0;
acl = ext4_get_acl(inode, ACL_TYPE_ACCESS);
if (IS_ERR(acl) || !acl)
return PTR_ERR(acl);
clone = posix_acl_clone(acl, GFP_KERNEL);
posix_acl_release(acl);
if (!clone)
return -ENOMEM;
error = posix_acl_chmod_masq(clone, inode->i_mode);
if (!error) {
handle_t *handle;
int retries = 0;
retry:
handle = ext4_journal_start(inode,
EXT4_DATA_TRANS_BLOCKS(inode->i_sb));
if (IS_ERR(handle)) {
error = PTR_ERR(handle);
ext4_std_error(inode->i_sb, error);
goto out;
}
error = ext4_set_acl(handle, inode, ACL_TYPE_ACCESS, clone);
ext4_journal_stop(handle);
if (error == -ENOSPC &&
ext4_should_retry_alloc(inode->i_sb, &retries))
goto retry;
}
out:
posix_acl_release(clone);
return error;
}
/*
* Extended attribute handlers
*/
static size_t
ext4_xattr_list_acl_access(struct inode *inode, char *list, size_t list_len,
const char *name, size_t name_len)
{
const size_t size = sizeof(POSIX_ACL_XATTR_ACCESS);
if (!test_opt(inode->i_sb, POSIX_ACL))
return 0;
if (list && size <= list_len)
memcpy(list, POSIX_ACL_XATTR_ACCESS, size);
return size;
}
static size_t
ext4_xattr_list_acl_default(struct inode *inode, char *list, size_t list_len,
const char *name, size_t name_len)
{
const size_t size = sizeof(POSIX_ACL_XATTR_DEFAULT);
if (!test_opt(inode->i_sb, POSIX_ACL))
return 0;
if (list && size <= list_len)
memcpy(list, POSIX_ACL_XATTR_DEFAULT, size);
return size;
}
static int
ext4_xattr_get_acl(struct inode *inode, int type, void *buffer, size_t size)
{
struct posix_acl *acl;
int error;
if (!test_opt(inode->i_sb, POSIX_ACL))
return -EOPNOTSUPP;
acl = ext4_get_acl(inode, type);
if (IS_ERR(acl))
return PTR_ERR(acl);
if (acl == NULL)
return -ENODATA;
error = posix_acl_to_xattr(acl, buffer, size);
posix_acl_release(acl);
return error;
}
static int
ext4_xattr_get_acl_access(struct inode *inode, const char *name,
void *buffer, size_t size)
{
if (strcmp(name, "") != 0)
return -EINVAL;
return ext4_xattr_get_acl(inode, ACL_TYPE_ACCESS, buffer, size);
}
static int
ext4_xattr_get_acl_default(struct inode *inode, const char *name,
void *buffer, size_t size)
{
if (strcmp(name, "") != 0)
return -EINVAL;
return ext4_xattr_get_acl(inode, ACL_TYPE_DEFAULT, buffer, size);
}
static int
ext4_xattr_set_acl(struct inode *inode, int type, const void *value,
size_t size)
{
handle_t *handle;
struct posix_acl *acl;
int error, retries = 0;
if (!test_opt(inode->i_sb, POSIX_ACL))
return -EOPNOTSUPP;
if (!is_owner_or_cap(inode))
return -EPERM;
if (value) {
acl = posix_acl_from_xattr(value, size);
if (IS_ERR(acl))
return PTR_ERR(acl);
else if (acl) {
error = posix_acl_valid(acl);
if (error)
goto release_and_out;
}
} else
acl = NULL;
retry:
handle = ext4_journal_start(inode, EXT4_DATA_TRANS_BLOCKS(inode->i_sb));
if (IS_ERR(handle))
return PTR_ERR(handle);
error = ext4_set_acl(handle, inode, type, acl);
ext4_journal_stop(handle);
if (error == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
goto retry;
release_and_out:
posix_acl_release(acl);
return error;
}
static int
ext4_xattr_set_acl_access(struct inode *inode, const char *name,
const void *value, size_t size, int flags)
{
if (strcmp(name, "") != 0)
return -EINVAL;
return ext4_xattr_set_acl(inode, ACL_TYPE_ACCESS, value, size);
}
static int
ext4_xattr_set_acl_default(struct inode *inode, const char *name,
const void *value, size_t size, int flags)
{
if (strcmp(name, "") != 0)
return -EINVAL;
return ext4_xattr_set_acl(inode, ACL_TYPE_DEFAULT, value, size);
}
struct xattr_handler ext4_xattr_acl_access_handler = {
.prefix = POSIX_ACL_XATTR_ACCESS,
.list = ext4_xattr_list_acl_access,
.get = ext4_xattr_get_acl_access,
.set = ext4_xattr_set_acl_access,
};
struct xattr_handler ext4_xattr_acl_default_handler = {
.prefix = POSIX_ACL_XATTR_DEFAULT,
.list = ext4_xattr_list_acl_default,
.get = ext4_xattr_get_acl_default,
.set = ext4_xattr_set_acl_default,
};
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