Re: [syzbot] KASAN: use-after-free Read in rxe_queue_cleanup

From: Pavel Skripkin
Date: Sat Nov 20 2021 - 10:02:14 EST

On 11/19/21 12:27, syzbot wrote:

syzbot found the following issue on:

HEAD commit: 8d0112ac6fd0 Merge tag 'net-5.16-rc2' of git://git.kernel...
git tree: net
console output:
kernel config:
dashboard link:
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+aab53008a5adf26abe91@xxxxxxxxxxxxxxxxxxxxxxxxx

Free swap = 0kB
Total swap = 0kB
2097051 pages RAM
0 pages HighMem/MovableOnly
384517 pages reserved
0 pages cma reserved
BUG: KASAN: use-after-free in rxe_queue_cleanup+0xf4/0x100 drivers/infiniband/sw/rxe/rxe_queue.c:193
Read of size 8 at addr ffff88814a6b6e90 by task syz-executor.3/9534

On error handling path in rxe_qp_from_init() qp->sq.queue is freed and then rxe_create_qp() will drop last reference to this object. qp clean up function will try to free this queue one time and it causes UAF bug.

Just for thoughts.

diff --git a/drivers/infiniband/sw/rxe/rxe_qp.c b/drivers/infiniband/sw/rxe/rxe_qp.c
index 975321812c87..54b8711321c1 100644
--- a/drivers/infiniband/sw/rxe/rxe_qp.c
+++ b/drivers/infiniband/sw/rxe/rxe_qp.c
@@ -359,6 +359,7 @@ int rxe_qp_from_init(struct rxe_dev *rxe, struct rxe_qp *qp, struct rxe_pd *pd,

+ qp->sq.queue = NULL;
qp->pd = NULL;
qp->rcq = NULL;

With regards,
Pavel Skripkin