Re: [Qemu-devel] [PATCH] virtio-net: fix wild pointer when remove virtio-net queues

[Jason Wang]

On 2017年04月26日 14:45, Yunjian Wang wrote:
The tx_bh or tx_timer will free in virtio_net_del_queue() function, when
removing virtio-net queues if the guest doesn't support multiqueue. But
it might be still referenced by virtio_net_set_status(), which needs to
be set NULL. And also the tx_waiting needs to be set zero to prevent
virtio_net_set_status() accessing tx_bh or tx_timer.

Signed-off-by: Yunjian Wang <wangyunj...@huawei.com>
---
  hw/net/virtio-net.c | 3 +++
  1 file changed, 3 insertions(+)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 7d091c9..98bd683 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1522,9 +1522,12 @@ static void virtio_net_del_queue(VirtIONet *n, int index)
      if (q->tx_timer) {
          timer_del(q->tx_timer);
          timer_free(q->tx_timer);
+        q->tx_timer = NULL;
      } else {
          qemu_bh_delete(q->tx_bh);
+        q->tx_bh = NULL;
      }
+    q->tx_waiting = 0;
      virtio_del_queue(vdev, index * 2 + 1);
  }
  

Thanks for the patch.

It looks to me that clearing tx_waiting is sufficient or is there any 
other reason that you need set tx_timer/tx_bh to NULL?

Thanks