[PATCH AUTOSEL 6.10 6/7] jfs: Fix shift-out-of-bounds in dbDiscardAG

Sasha Levin
2024-07-30T12:45:34Z

From: Pei Li <peili.dev@gmail.com>

[ Upstream commit 7063b80268e2593e58bee8a8d709c2f3ff93e2f2 ]

When searching for the next smaller log2 block, BLKSTOL2() returned 0,
causing shift exponent -1 to be negative.

This patch fixes the issue by exiting the loop directly when negative
shift is found.

Reported-by: syzbot+61be3359d2ee3467e7e4@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=61be3359d2ee3467e7e4
Signed-off-by: Pei Li <peili.dev@gmail.com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/jfs/jfs_dmap.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index cb3cda1390adb..5713994328cbc 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -1626,6 +1626,8 @@ s64 dbDiscardAG(struct inode *ip, int agno, s64 minlen)
} else if (rc == -ENOSPC) {
/* search for next smaller log2 block */
l2nb = BLKSTOL2(nblocks) - 1;
+ if (unlikely(l2nb < 0))
+ break;
nblocks = 1LL << l2nb;
} else {
/* Trim any already allocated blocks */
--
2.43.0