When the value of lp is 1 at the end of the iteration in the for loop,
lp is modified in the next iteration to a negative value.
Add a check to prevent this condition.

Reported-by: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=412dea214d8baa3f7483
Tested-by: [email protected]
Signed-off-by: Nihar Chaithanya <[email protected]>
---
 fs/jfs/jfs_dmap.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index 5713994328cb..3ebb2dfdd0b3 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -2911,6 +2911,12 @@ static void dbAdjTree(dmtree_t *tp, int leafno, int 
newval, bool is_ctl)
                 */
                tp->dmt_stree[pp] = max;
 
+               /* check to prevent negative value of lp on the
+                * next iteration.
+                */
+               if (lp == 1)
+                       break;
+
                /* parent becomes leaf for next go-round.
                 */
                lp = pp;
-- 
2.34.1


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