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Subject[PATCH] fs: jfs: fix shift-out-of-bounds in dbDiscardAG
Date
Bug reported by syzbot, UBSAN: array-index-out-of-bounds in dbDiscardAG.
Fixed by simply rearranging agno_end smaller than MAXAG. However, I wonder if it
is a better idea to return -EINVAL, rejecting user input. Thank you.

Reported-by: syzbot+f0e0fcf3cd1047ae60ad@syzkaller.appspotmail.com
Signed-off-by: Hoi Pok Wu <wuhoipok@gmail.com>
---
fs/jfs/jfs_discard.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/fs/jfs/jfs_discard.c b/fs/jfs/jfs_discard.c
index 575cb2ba74fc..3101eaf3098a 100644
--- a/fs/jfs/jfs_discard.c
+++ b/fs/jfs/jfs_discard.c
@@ -96,6 +96,10 @@ int jfs_ioc_trim(struct inode *ip, struct fstrim_range *range)
*/
agno = BLKTOAG(start, JFS_SBI(ip->i_sb));
agno_end = BLKTOAG(end, JFS_SBI(ip->i_sb));
+
+ if (agno_end >= MAXAG)
+ agno_end = MAXAG - 1;
+
while (agno <= agno_end) {
trimmed += dbDiscardAG(ip, agno, minlen);
agno++;
--
2.38.0
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