There is a lack of verification of the space occupied by fixed members
of xlog_op_header in the xlog_recover_process_data.
We can create a crafted image to trigger an out of bounds read by
following these steps:
1) Mount an image of xfs, and do some file operations to leave records
2) Before umounting, copy the image for subsequent steps to simulate
abnormal exit. Because umount will ensure that tail_blk and
head_blk are the same, which will result in the inability to enter
xlog_recover_process_data
3) Write a tool to parse and modify the copied image in step 2
4) Make the end of the xlog_op_header entries only 1 byte away from
xlog_rec_header->h_size
5) xlog_rec_header->h_num_logops++
6) Modify xlog_rec_header->h_crc
Fix:
Add a check to make sure there is sufficient space to access fixed members
of xlog_op_header.
Signed-off-by: lei lu <llfamsec@xxxxxxxxx>
---
fs/xfs/xfs_log_recover.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 1251c81e55f9..14609ce212db 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -2456,7 +2456,10 @@ xlog_recover_process_data(
ohead = (struct xlog_op_header *)dp;
dp += sizeof(*ohead);
- ASSERT(dp <= end);
+ if (dp > end) {
+ xfs_warn(log->l_mp, "%s: op header overrun", __func__);
+ return -EFSCORRUPTED;
+ }
/* errors will abort recovery */
error = xlog_recover_process_ophdr(log, rhash, rhead, ohead,
--
2.34.1
