Re: [PATCH] vhost: fix dereference null return value

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

On Wed, Jun 15, 2016 at 08:32:45AM +0800, Huawei Xie wrote:
> fixes the following coverity issues:
> CID 107118 (#1 of 1): Dereference null return value (NULL_RETURNS)
> CID 119262 (#1 of 1): Dereference null return value (NULL_RETURNS)
> 
> Fixes: 8f972312b8f4 ("vhost: support vhost-user")
> Fixes: 77d20126b4c2 ("vhost-user: handle message to enable vring")
> 
> Signed-off-by: Huawei Xie <huawei.xie@intel.com>
> ---
>  lib/librte_vhost/vhost_user/virtio-net-user.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/librte_vhost/vhost_user/virtio-net-user.c b/lib/librte_vhost/vhost_user/virtio-net-user.c
> index 5803182..5844a42 100644
> --- a/lib/librte_vhost/vhost_user/virtio-net-user.c
> +++ b/lib/librte_vhost/vhost_user/virtio-net-user.c
> @@ -283,6 +283,9 @@ user_set_vring_kick(struct vhost_device_ctx ctx, struct VhostUserMsg *pmsg)
>  	struct vhost_vring_file file;
>  	struct virtio_net *dev = get_device(ctx);
>  
> +	if (!dev)
> +		return;
> +

I just found that it's been fixed by commit a03aabf2e8d6 ("vhost: export
vid as the only interface to applications"), "accidentally".

>  	file.index = pmsg->payload.u64 & VHOST_USER_VRING_IDX_MASK;
>  	if (pmsg->payload.u64 & VHOST_USER_VRING_NOFD_MASK)
>  		file.fd = VIRTIO_INVALID_EVENTFD;
> @@ -306,8 +309,9 @@ user_get_vring_base(struct vhost_device_ctx ctx,
>  {
>  	struct virtio_net *dev = get_device(ctx);
>  
> -	if (dev == NULL)
> +	if (!dev)
>  		return -1;

What's that for? Interestingly, if you look at the DPDK coding style,
you will find that it's encouraged to use "dev == NULL" check instead
of the "!dev" check. I sometimes uses both though.

So, I don't think it's a big deal, and I will leave it as it is.

> +
>  	/* We have to stop the queue (virtio) if it is running. */
>  	if (dev->flags & VIRTIO_DEV_RUNNING)
>  		notify_ops->destroy_device(dev);
> @@ -341,6 +345,9 @@ user_set_vring_enable(struct vhost_device_ctx ctx,
>  	struct virtio_net *dev = get_device(ctx);
>  	int enable = (int)state->num;
>  
> +	if (!dev)
> +		return -1;
> +

It's been fixed by commit 590a936287c6 ("vhost: fix null pointer
dereference").

So, sorry, I will NACK this patch.

	--yliu