Re: [PATCH net V2] vhost: correctly remove wait queue during poll failure

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On Tue, Mar 27, 2018 at 08:50:52PM +0800, Jason Wang wrote:
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@xxxxxxxxxx>
Reported-by: syzbot+c0272972b01b872e604a@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 2b8b328b61c79 ("vhost_net: handle polling errors when setting backend")
Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>

Reviewed-by: Darren Kenny <darren.kenny@xxxxxxxxxx>

---
Changes from V1:
- tweak the commit log for to match the code
---
drivers/vhost/vhost.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 1b3e8d2d..5d5a9d9 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -212,8 +212,7 @@ int vhost_poll_start(struct vhost_poll *poll, struct file *file)
	if (mask)
		vhost_poll_wakeup(&poll->wait, 0, 0, poll_to_key(mask));
	if (mask & EPOLLERR) {
-		if (poll->wqh)
-			remove_wait_queue(poll->wqh, &poll->wait);
+		vhost_poll_stop(poll);
		ret = -EINVAL;
	}

--
2.7.4




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