queue-6.1/vsock-virtio-flush-works-in-dependency-order.patch

From 728836ebca239810f164262b10211ef59182f811 Mon Sep 17 00:00:00 2001
From: Chengfeng Ye <nicoyip.dev@gmail.com>
Date: Sun, 23 Aug 2026 00:45:56 +0800
Subject: vsock/virtio: flush works in dependency order

From: Chengfeng Ye <nicoyip.dev@gmail.com>

commit 728836ebca239810f164262b10211ef59182f811 upstream.

virtio_vsock_remove() stops the virtqueues and then flushes each work
item before freeing the enclosing virtio_vsock.  The current order does
not account for dependencies between those items: tx_work may queue
send_pkt_work, and send_pkt_work may queue rx_work.

In particular, send_pkt_work can set restart_rx and release tx_lock.
The remove path can then stop the queues and flush rx_work before
send_pkt_work queues it.  Although the later send_pkt_work flush waits
for that producer to finish, nothing waits for the newly queued rx_work,
so kfree(vsock) can race with it.

KASAN reported:

  BUG: KASAN: slab-use-after-free in
  virtio_transport_rx_work+0x487/0x4b0
  Read of size 8 at addr ffff888114c2b008 by task kworker/1:1/47
  Workqueue: virtio_vsock virtio_transport_rx_work
  Call Trace:
   virtio_transport_rx_work+0x487/0x4b0
   process_one_work+0x688/0x1120
   worker_thread+0x45b/0xd10
  Allocated by task 1:
   virtio_vsock_probe+0xef/0x6b0
  Freed by task 84:
   kfree+0x131/0x3c0
   virtio_vsock_remove+0xd1/0x100

Flush the works in producer-to-consumer order.  virtio_vsock_vqs_del()
has already disabled the queue callbacks and cleared the run flags, so
after tx_work and send_pkt_work are drained, no source remains that can
queue rx_work after its flush.

Fixes: 0ea9e1d3a9e3 ("VSOCK: Introduce virtio_transport.ko")
Cc: stable@vger.kernel.org
Signed-off-by: Chengfeng Ye <nicoyip.dev@gmail.com>
Link: https://patch.msgid.link/20260822164556.3750959-1-nicoyip.dev@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/vmw_vsock/virtio_transport.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -714,10 +714,10 @@ static void virtio_vsock_remove(struct v
 	/* Other works can be queued before 'config->del_vqs()', so we flush
 	 * all works before to free the vsock object to avoid use after free.
 	 */
-	flush_work(&vsock->rx_work);
 	flush_work(&vsock->tx_work);
 	flush_work(&vsock->event_work);
 	flush_work(&vsock->send_pkt_work);
+	flush_work(&vsock->rx_work);
 
 	mutex_unlock(&the_virtio_vsock_mutex);