RE: [PATCH] virtio/vhost-user: Fix wrong vhost notifier GPtrArray size

From: Yajun Wu <yajunw@nvidia.com>
To: "Alex Bennée" <alex.bennee@linaro.org>,
	"mst@redhat.com" <mst@redhat.com>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
	Parav Pandit <parav@nvidia.com>
Subject: RE: [PATCH] virtio/vhost-user: Fix wrong vhost notifier GPtrArray size
Date: Tue, 14 Jun 2022 01:33:50 +0000	[thread overview]
Message-ID: <DM4PR12MB516883266752C2A5B063304EB6AA9@DM4PR12MB5168.namprd12.prod.outlook.com> (raw)
In-Reply-To: <874k1c22i3.fsf@linaro.org>

Hi Michael,

User space vhost clients are broken for few weeks now without this fix.
With Alex's review, can you please merge it if there are no further comments?

Thanks.

-----Original Message-----
From: Alex Bennée <alex.bennee@linaro.org> 
Sent: Thursday, May 26, 2022 3:09 PM
To: Yajun Wu <yajunw@nvidia.com>
Cc: qemu-devel@nongnu.org; mst@redhat.com; Parav Pandit <parav@nvidia.com>
Subject: Re: [PATCH] virtio/vhost-user: Fix wrong vhost notifier GPtrArray size

External email: Use caution opening links or attachments

Yajun Wu <yajunw@nvidia.com> writes:

> In fetch_or_create_notifier, idx begins with 0. So the GPtrArray size 
> should be idx + 1 and g_ptr_array_set_size should be called with idx + 1.
>
> This wrong GPtrArray size causes fetch_or_create_notifier return an 
> invalid address. Passing this invalid pointer to 
> vhost_user_host_notifier_remove causes assert fail:
>
>     qemu/include/qemu/int128.h:27: int128_get64: Assertion `r == a' failed.
>       shutting down, reason=crashed
>
> Backends like dpdk-vdpa which sends out vhost notifier requests almost 
> always hit qemu crash.

My bad. I was looking for ways to exercise this code but the internal tests didn't do it. I guess I should look at getting a test setup for dpdk. Anyway:

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

>
> Fixes: 503e355465 ("virtio/vhost-user: dynamically assign 
> VhostUserHostNotifiers")
> Signed-off-by: Yajun Wu <yajunw@nvidia.com>
> Acked-by: Parav Pandit <parav@nvidia.com>
> Change-Id: I87e0f7591ca9a59d210879b260704a2d9e9d6bcd
> ---
>  hw/virtio/vhost-user.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c index 
> b040c1ad2b..dbc690d16c 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -1525,7 +1525,7 @@ static VhostUserHostNotifier 
> *fetch_or_create_notifier(VhostUserState *u,  {
>      VhostUserHostNotifier *n = NULL;
>      if (idx >= u->notifiers->len) {
> -        g_ptr_array_set_size(u->notifiers, idx);
> +        g_ptr_array_set_size(u->notifiers, idx + 1);
>      }
>
>      n = g_ptr_array_index(u->notifiers, idx);

--
Alex Bennée