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ext4: fix bounds check in check_xattrs() to prevent out-of-bounds access

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The bounds check for the next xattr entry in check_xattrs() uses
(void *)next >= end, which allows next to point within sizeof(u32)
bytes of end. On the next loop iteration, IS_LAST_ENTRY() reads 4
bytes via *(__u32 *)(entry), which can overrun the valid xattr region.

For example, if next lands at end - 1, the check passes since
next < end, but IS_LAST_ENTRY() reads 4 bytes starting at end - 1,
accessing 3 bytes beyond the valid region.

Fix this by changing the check to (void *)next + sizeof(u32) > end,
ensuring there is always enough space for the IS_LAST_ENTRY() read
on the subsequent iteration.

Fixes: 3478c83cf2 ("ext4: improve xattr consistency checking and error reporting")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20260224231429.31361-1-kartikey406@gmail.com/T/ [v1]
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
Link: https://patch.msgid.link/20260328150038.349497-1-kartikey406@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Deepanshu Kartikey 2026-03-28 20:30:38 +05:30 committed by Theodore Ts'o
parent 3f60efd654
commit eceafc31ea
1 changed files with 1 additions and 1 deletions
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2
fs/ext4/xattr.c
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@ -226,7 +226,7 @@ check_xattrs(struct inode *inode, struct buffer_head *bh,
/* Find the end of the names list */
while (!IS_LAST_ENTRY(e)) {
struct ext4_xattr_entry *next = EXT4_XATTR_NEXT(e);
if ((void *)next >= end) {
if ((void *)next + sizeof(u32) > end) {
err_str = "e_name out of bounds";
goto errout;
}