Re: [PATCH] jfs: array-index-out-of-bounds fix in dtReadFirst

From: Dave Kleikamp
Date: Tue Oct 29 2024 - 17:35:15 EST


On 9/28/24 3:37AM, Ghanshyam Agrawal wrote:
The value of stbl can be sometimes out of bounds due
to a bad filesystem. Added a check with appopriate return
of error code in that case.

Reported-by: syzbot+65fa06e29859e41a83f3@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=65fa06e29859e41a83f3
Signed-off-by: Ghanshyam Agrawal <ghanshyam1898@xxxxxxxxx>
---
fs/jfs/jfs_dtree.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/fs/jfs/jfs_dtree.c b/fs/jfs/jfs_dtree.c
index 5d3127ca68a4..69fd936fbdb3 100644
--- a/fs/jfs/jfs_dtree.c
+++ b/fs/jfs/jfs_dtree.c
@@ -3086,6 +3086,13 @@ static int dtReadFirst(struct inode *ip, struct btstack * btstack)
/* get the leftmost entry */
stbl = DT_GETSTBL(p);
+
+ if (stbl[0] < 0 || stbl[0] > 127) {

Technically, a signed 8-bit integer cannot exceed 127, but since the compiler will know that and optimize it out, I'll leave it in because it looks more complete.

+ 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 */

Looks good. I'll apply this.

Shaggy