releases/4.15.17/vhost-correctly-remove-wait-queue-during-poll-failure.patch

   1 From foo@baz Tue Apr 10 23:19:36 CEST 2018
   2 From: Jason Wang <jasowang@redhat.com>
   3 Date: Tue, 27 Mar 2018 20:50:52 +0800
   4 Subject: vhost: correctly remove wait queue during poll failure
   5
   6 From: Jason Wang <jasowang@redhat.com>
   7
   8
   9 [ Upstream commit dc6455a71c7fc5117977e197f67f71b49f27baba ]
  10
  11 We tried to remove vq poll from wait queue, but do not check whether
  12 or not it was in a list before. This will lead double free. Fixing
  13 this by switching to use vhost_poll_stop() which zeros poll->wqh after
  14 removing poll from waitqueue to make sure it won't be freed twice.
  15
  16 Cc: Darren Kenny <darren.kenny@oracle.com>
  17 Reported-by: syzbot+c0272972b01b872e604a@syzkaller.appspotmail.com
  18 Fixes: 2b8b328b61c79 ("vhost_net: handle polling errors when setting backend")
  19 Signed-off-by: Jason Wang <jasowang@redhat.com>
  20 Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
  21 Acked-by: Michael S. Tsirkin <mst@redhat.com>
  22 Signed-off-by: David S. Miller <davem@davemloft.net>
  23 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  24 ---
  25  drivers/vhost/vhost.c |    3 +--
  26  1 file changed, 1 insertion(+), 2 deletions(-)
  27
  28 --- a/drivers/vhost/vhost.c
  29 +++ b/drivers/vhost/vhost.c
  30 @@ -213,8 +213,7 @@ int vhost_poll_start(struct vhost_poll *
  31         if (mask)
  32                 vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
  33         if (mask & POLLERR) {
  34 -               if (poll->wqh)
  35 -                       remove_wait_queue(poll->wqh, &poll->wait);
  36 +               vhost_poll_stop(poll);
  37                 ret = -EINVAL;
  38         }
  39