vhost_net: handle polling errors when setting backend
Currently, the polling errors were ignored, which can lead following issues:
- vhost remove itself unconditionally from waitqueue when stopping the poll,
this may crash the kernel since the previous attempt of starting may fail to
add itself to the waitqueue
- userspace may think the backend were successfully set even when the polling
failed.
Solve this by:
- check poll->wqh before trying to remove from waitqueue
- report polling errors in vhost_poll_start(), tx_poll_start(), the return value
will be checked and returned when userspace want to set the backend
After this fix, there still could be a polling failure after backend is set, it
will addressed by the next patch.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 34389f7..9759249 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -77,26 +77,38 @@
init_poll_funcptr(&poll->table, vhost_poll_func);
poll->mask = mask;
poll->dev = dev;
+ poll->wqh = NULL;
vhost_work_init(&poll->work, fn);
}
/* Start polling a file. We add ourselves to file's wait queue. The caller must
* keep a reference to a file until after vhost_poll_stop is called. */
-void vhost_poll_start(struct vhost_poll *poll, struct file *file)
+int vhost_poll_start(struct vhost_poll *poll, struct file *file)
{
unsigned long mask;
+ int ret = 0;
mask = file->f_op->poll(file, &poll->table);
if (mask)
vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
+ if (mask & POLLERR) {
+ if (poll->wqh)
+ remove_wait_queue(poll->wqh, &poll->wait);
+ ret = -EINVAL;
+ }
+
+ return ret;
}
/* Stop polling a file. After this function returns, it becomes safe to drop the
* file reference. You must also flush afterwards. */
void vhost_poll_stop(struct vhost_poll *poll)
{
- remove_wait_queue(poll->wqh, &poll->wait);
+ if (poll->wqh) {
+ remove_wait_queue(poll->wqh, &poll->wait);
+ poll->wqh = NULL;
+ }
}
static bool vhost_work_seq_done(struct vhost_dev *dev, struct vhost_work *work,
@@ -792,7 +804,7 @@
fput(filep);
if (pollstart && vq->handle_kick)
- vhost_poll_start(&vq->poll, vq->kick);
+ r = vhost_poll_start(&vq->poll, vq->kick);
mutex_unlock(&vq->mutex);