jfs: add a check to prevent array-index-out-of-bounds in dbAdjTree

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@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=412dea214d8baa3f7483
Tested-by: syzbot+412dea214d8baa3f7483@syzkaller.appspotmail.com
Signed-off-by: Nihar Chaithanya <niharchaithanya@gmail.com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index 3995736..f9009e4 100644 (file)
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -2891,6 +2891,9 @@ 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).
                 */