Re: [PATCH V2] jfs: check if leafidx greater than num leaves per dmap tree

From: Dave Kleikamp
Date: Fri Aug 23 2024 - 14:30:45 EST


On 7/26/24 8:42PM, Edward Adam Davis wrote:
syzbot report a out of bounds in dbSplit, it because dmt_leafidx greater
than num leaves per dmap tree, add a checking for dmt_leafidx in dbFindLeaf.

Reported-and-tested-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 | 2 ++
1 file changed, 2 insertions(+)

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index cb3cda1390ad..516bac758053 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -2976,6 +2976,8 @@ static int dbFindLeaf(dmtree_t *tp, int l2nb, int *leafidx, bool is_ctl)
*/
assert(n < 4);
}
+ if (le32_to_cpu(tp->dmt_leafidx) >= LPERDMAP)
+ return -ENOSPC;

NACK. It needs to be smarter than this.

dbFindLeaf() can be called with a control page in which dmt_leafidx is bound by LPERCTL, which is larger than LPERDMAP.

/* set the return to the leftmost leaf describing sufficient
* free space.