[PATCH] jfs: check if dmt_leafidx is less than zero

[Edward Adam Davis]

syzbot report a out of bounds in dbSplit, it because dmt_leafidx less
than 0, add a checking for dmt_leafidx in dbAllocDmapLev.

Reported-by: syzbot+dca05492eff41f604890@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=dca05492eff41f604890
Signed-off-by: Edward Adam Davis <eadavis@xxxxxx>
---
 fs/jfs/jfs_dmap.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index cb3cda1390ad..c5b8883599e3 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -1956,6 +1956,7 @@ dbAllocDmapLev(struct bmap * bmp,
 {
 	s64 blkno;
 	int leafidx, rc;
+	dmtree_t *tp = (dmtree_t *) &dp->tree;
 
 	/* can't be more than a dmaps worth of blocks */
 	assert(l2nb <= L2BPERDMAP);
@@ -1964,10 +1965,10 @@ dbAllocDmapLev(struct bmap * bmp,
 	 * free space.  if sufficient free space is found, dbFindLeaf()
 	 * returns the index of the leaf at which free space was found.
 	 */
-	if (dbFindLeaf((dmtree_t *) &dp->tree, l2nb, &leafidx, false))
+	if (dbFindLeaf(tp, l2nb, &leafidx, false))
 		return -ENOSPC;
 
-	if (leafidx < 0)
+	if (leafidx < 0 || le32_to_cpu(tp->dmt_leafidx) < 0)
 		return -EIO;
 
 	/* determine the block number within the file system corresponding
-- 
2.43.0