diff options
| author | Tejas Bharambe <tejas.bharambe@outlook.com> | 2026-03-03 23:14:34 -0800 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2026-03-27 23:33:46 -0400 |
| commit | 2acb5c12ebd860f30e4faf67e6cc8c44ddfe5fe8 (patch) | |
| tree | 28e15cdc68b982d6b6423b5f66ddab4a18da8310 | |
| parent | 73bf12adbea10b13647864cd1c62410d19e21086 (diff) | |
ext4: validate p_idx bounds in ext4_ext_correct_indexes
ext4_ext_correct_indexes() walks up the extent tree correcting
index entries when the first extent in a leaf is modified. Before
accessing path[k].p_idx->ei_block, there is no validation that
p_idx falls within the valid range of index entries for that
level.
If the on-disk extent header contains a corrupted or crafted
eh_entries value, p_idx can point past the end of the allocated
buffer, causing a slab-out-of-bounds read.
Fix this by validating path[k].p_idx against EXT_LAST_INDEX() at
both access sites: before the while loop and inside it. Return
-EFSCORRUPTED if the index pointer is out of range, consistent
with how other bounds violations are handled in the ext4 extent
tree code.
Reported-by: syzbot+04c4e65cab786a2e5b7e@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=04c4e65cab786a2e5b7e
Signed-off-by: Tejas Bharambe <tejas.bharambe@outlook.com>
Link: https://patch.msgid.link/JH0PR06MB66326016F9B6AD24097D232B897CA@JH0PR06MB6632.apcprd06.prod.outlook.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
| -rw-r--r-- | fs/ext4/extents.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index b41a44dc245c..c99e0802d700 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -1736,6 +1736,13 @@ static int ext4_ext_correct_indexes(handle_t *handle, struct inode *inode, err = ext4_ext_get_access(handle, inode, path + k); if (err) return err; + if (unlikely(path[k].p_idx > EXT_LAST_INDEX(path[k].p_hdr))) { + EXT4_ERROR_INODE(inode, + "path[%d].p_idx %p > EXT_LAST_INDEX %p", + k, path[k].p_idx, + EXT_LAST_INDEX(path[k].p_hdr)); + return -EFSCORRUPTED; + } path[k].p_idx->ei_block = border; err = ext4_ext_dirty(handle, inode, path + k); if (err) @@ -1748,6 +1755,14 @@ static int ext4_ext_correct_indexes(handle_t *handle, struct inode *inode, err = ext4_ext_get_access(handle, inode, path + k); if (err) goto clean; + if (unlikely(path[k].p_idx > EXT_LAST_INDEX(path[k].p_hdr))) { + EXT4_ERROR_INODE(inode, + "path[%d].p_idx %p > EXT_LAST_INDEX %p", + k, path[k].p_idx, + EXT_LAST_INDEX(path[k].p_hdr)); + err = -EFSCORRUPTED; + goto clean; + } path[k].p_idx->ei_block = border; err = ext4_ext_dirty(handle, inode, path + k); if (err) |