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ext4: check EA value offset when loading

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When loading extended attributes, check each entry's value offset to
make sure it doesn't collide with the entries.

Without this check it is easy to crash the kernel by mounting a
malicious FS containing a file with an EA wherein e_value_offs = 0 and
e_value_size > 0 and then deleting the EA, which corrupts the name
list.

(See the f_ea_value_crash test's FS image in e2fsprogs for an example.)

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
This commit is contained in:
Darrick J. Wong 2014-09-16 14:34:59 -04:00 committed by Theodore Ts'o
parent 684de57486
commit a0626e7595
1 changed files with 24 additions and 8 deletions
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32
fs/ext4/xattr.c
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@ -190,14 +190,28 @@ ext4_listxattr(struct dentry *dentry, char *buffer, size_t size)
}
static int
ext4_xattr_check_names(struct ext4_xattr_entry *entry, void *end)
ext4_xattr_check_names(struct ext4_xattr_entry *entry, void *end,
void *value_start)
{
while (!IS_LAST_ENTRY(entry)) {
struct ext4_xattr_entry *next = EXT4_XATTR_NEXT(entry);
struct ext4_xattr_entry *e = entry;
while (!IS_LAST_ENTRY(e)) {
struct ext4_xattr_entry *next = EXT4_XATTR_NEXT(e);
if ((void *)next >= end)
return -EIO;
entry = next;
e = next;
}
while (!IS_LAST_ENTRY(entry)) {
if (entry->e_value_size != 0 &&
(value_start + le16_to_cpu(entry->e_value_offs) <
(void *)e + sizeof(__u32) ||
value_start + le16_to_cpu(entry->e_value_offs) +
le32_to_cpu(entry->e_value_size) > end))
return -EIO;
entry = EXT4_XATTR_NEXT(entry);
}
return 0;
}
@ -214,7 +228,8 @@ ext4_xattr_check_block(struct inode *inode, struct buffer_head *bh)
return -EIO;
if (!ext4_xattr_block_csum_verify(inode, bh->b_blocknr, BHDR(bh)))
return -EIO;
error = ext4_xattr_check_names(BFIRST(bh), bh->b_data + bh->b_size);
error = ext4_xattr_check_names(BFIRST(bh), bh->b_data + bh->b_size,
bh->b_data);
if (!error)
set_buffer_verified(bh);
return error;
@ -331,7 +346,7 @@ ext4_xattr_ibody_get(struct inode *inode, int name_index, const char *name,
header = IHDR(inode, raw_inode);
entry = IFIRST(header);
end = (void *)raw_inode + EXT4_SB(inode->i_sb)->s_inode_size;
error = ext4_xattr_check_names(entry, end);
error = ext4_xattr_check_names(entry, end, entry);
if (error)
goto cleanup;
error = ext4_xattr_find_entry(&entry, name_index, name,
@ -463,7 +478,7 @@ ext4_xattr_ibody_list(struct dentry *dentry, char *buffer, size_t buffer_size)
raw_inode = ext4_raw_inode(&iloc);
header = IHDR(inode, raw_inode);
end = (void *)raw_inode + EXT4_SB(inode->i_sb)->s_inode_size;
error = ext4_xattr_check_names(IFIRST(header), end);
error = ext4_xattr_check_names(IFIRST(header), end, IFIRST(header));
if (error)
goto cleanup;
error = ext4_xattr_list_entries(dentry, IFIRST(header),
@ -980,7 +995,8 @@ int ext4_xattr_ibody_find(struct inode *inode, struct ext4_xattr_info *i,
is->s.here = is->s.first;
is->s.end = (void *)raw_inode + EXT4_SB(inode->i_sb)->s_inode_size;
if (ext4_test_inode_state(inode, EXT4_STATE_XATTR)) {
error = ext4_xattr_check_names(IFIRST(header), is->s.end);
error = ext4_xattr_check_names(IFIRST(header), is->s.end,
IFIRST(header));
if (error)
return error;
/* Find the named attribute. */