vhost: correctly remove wait queue during poll failure

BugLink: http://bugs.launchpad.net/bugs/1763366
[ Upstream commit dc6455a71c7fc5117977e197f67f71b49f27baba ]

We tried to remove vq poll from wait queue, but do not check whether
or not it was in a list before. This will lead double free. Fixing
this by switching to use vhost_poll_stop() which zeros poll->wqh after
removing poll from waitqueue to make sure it won't be freed twice.

Cc: Darren Kenny <darren.kenny@oracle.com>
Reported-by: syzbot+c0272972b01b872e604a@syzkaller.appspotmail.com
Fixes: 2b8b328b61c79 ("vhost_net: handle polling errors when setting backend")
Signed-off-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 5727b186b3ca56b6d43249bc69eb7f962bd22308..f42683578dcabd832b0e6204e2ec0b4497c5705f 100644 (file)
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -213,8 +213,7 @@ int vhost_poll_start(struct vhost_poll *poll, struct file *file)
        if (mask)
                vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
        if (mask & POLLERR) {
-               if (poll->wqh)
-                       remove_wait_queue(poll->wqh, &poll->wait);
+               vhost_poll_stop(poll);
                ret = -EINVAL;
        }