[PATCH] jfs: fix array-index-out-of-bounds in dbFindLeaf

[Manas Ghandat <ghandatmanas@gmail.com>]

Currently while searching for dmtree_t for sufficient free blocks there
is an array out of bounds while getting element in tp->dm_stree. Added
the required bound check.

Ps: After I added the check I am getting the following log

[   22.661748][ T4425] ERROR: (device loop0): dbAllocAny: unable to allocate blocks
[   22.661748][ T4425]
[   22.665536][ T4425] ERROR: (device loop0): remounting filesystem as read-only
[   22.667856][ T4425] jfs_mkdir: dtInsert returned -EIO
[   22.669750][ T4425] ERROR: (device loop0): txAbort:

I was wondering if these checks are significant of not?

Signed-off-by: Manas Ghandat <ghandatmanas@gmail.com>
Reported-by: syzbot+aea1ad91e854d0a83e04@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=aea1ad91e854d0a83e04
---
 fs/jfs/jfs_dmap.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index a14a0f18a4c4..5af17b2287be 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -2948,6 +2948,10 @@ static int dbFindLeaf(dmtree_t * tp, int l2nb, int *leafidx)
 			/* sufficient free space found.  move to the next
 			 * level (or quit if this is the last level).
 			 */
+
+			if (x + n > TREESIZE)
+				return -ENOSPC;
+
 			if (l2nb <= tp->dmt_stree[x + n])
 				break;
 		}
-- 
2.37.2