[PATCH AUTOSEL 5.4 19/28] jfs: add a check to prevent array-index-out-of-bounds in dbAdjTree

[Sasha Levin]

From: Nihar Chaithanya <niharchaithanya@xxxxxxxxx>

[ Upstream commit a174706ba4dad895c40b1d2277bade16dfacdcd9 ]

When the value of lp is 0 at the beginning of the for loop, it will
become negative in the next assignment and we should bail out.

Reported-by: syzbot+412dea214d8baa3f7483@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=412dea214d8baa3f7483
Tested-by: syzbot+412dea214d8baa3f7483@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Nihar Chaithanya <niharchaithanya@xxxxxxxxx>
Signed-off-by: Dave Kleikamp <dave.kleikamp@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/jfs/jfs_dmap.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index d83ac5f5888a4..812945c8e3840 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -2953,6 +2953,9 @@ static void dbAdjTree(dmtree_t *tp, int leafno, int newval, bool is_ctl)
 	/* bubble the new value up the tree as required.
 	 */
 	for (k = 0; k < le32_to_cpu(tp->dmt_height); k++) {
+		if (lp == 0)
+			break;
+
 		/* get the index of the first leaf of the 4 leaf
 		 * group containing the specified leaf (leafno).
 		 */
-- 
2.43.0