Re: [syzbot] [jfs?] UBSAN: array-index-out-of-bounds in dtReadFirst

[Edward Adam Davis]

please test oob in dtReadFirst

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 5eb4573ea63d

diff --git a/fs/jfs/jfs_dtree.c b/fs/jfs/jfs_dtree.c
index 5d3127ca68a4..f5d5467a49e6 100644
--- a/fs/jfs/jfs_dtree.c
+++ b/fs/jfs/jfs_dtree.c
@@ -3086,6 +3086,11 @@ static int dtReadFirst(struct inode *ip, struct btstack * btstack)
 
 		/* get the leftmost entry */
 		stbl = DT_GETSTBL(p);
+		if (stbl[0] < 0 || stbl[0] > 127) {
+			DT_PUTPAGE(mp);
+			jfs_error(ip->i_sb, "stbl[0] out of bound\n");
+			return -EIO;
+		}
 		xd = (pxd_t *) & p->slot[stbl[0]];
 
 		/* get the child page block address */