[dpdk-stable] [18.11 LTS PATCH] vhost: fix vring requests validation broken if no FD

[Tiwei Bie]

On Thu, Nov 14, 2019 at 04:16:29PM +0100, Maxime Coquelin wrote:
> From: Zhike Wang <wangzk320 at 163.com>
> 
> When VHOST_USER_VRING_NOFD_MASK is set, the fd_num is 0,
> so validate_msg_fds() will return error. In this case,
> the negotiation of vring message between vhost user front end and
> back end would fail, and as a result, vhost user link could NOT be up.
> 
> How to reproduce:
> 1.Run dpdk testpmd insides VM, which locates at host with ovs+dpdk.
> 2.Notice that inside ovs there are endless logs regarding failure to
> handle VHOST_USER_SET_VRING_CALL, and link of vm could NOT be up.
> 
> Fixes: f8898927bb16 ("vhost: fix possible denial of service by leaking FDs")
> Cc: stable at dpdk.org
> 
> Signed-off-by: Zhike Wang <wangzk320 at 163.com>
> Reviewed-by: Maxime Coquelin <maxime.coquelin at redhat.com>
> ---

Reviewed-by: Tiwei Bie <tiwei.bie at intel.com>

Thanks!
Tiwei

> 
> Backport not tested yet.
> 
>  lib/librte_vhost/vhost_user.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
> index 98cd670e03..530823ecd9 100644
> --- a/lib/librte_vhost/vhost_user.c
> +++ b/lib/librte_vhost/vhost_user.c
> @@ -1241,8 +1241,10 @@ vhost_user_set_vring_call(struct virtio_net **pdev, struct VhostUserMsg *msg,
>  	struct virtio_net *dev = *pdev;
>  	struct vhost_vring_file file;
>  	struct vhost_virtqueue *vq;
> +	int expected_fds;
>  
> -	if (validate_msg_fds(msg, 1) != 0)
> +	expected_fds = (msg->payload.u64 & VHOST_USER_VRING_NOFD_MASK) ? 0 : 1;
> +	if (validate_msg_fds(msg, expected_fds) != 0)
>  		return VH_RESULT_ERR;
>  
>  	file.index = msg->payload.u64 & VHOST_USER_VRING_IDX_MASK;
> @@ -1266,7 +1268,10 @@ static int vhost_user_set_vring_err(struct virtio_net **pdev __rte_unused,
>  			struct VhostUserMsg *msg,
>  			int main_fd __rte_unused)
>  {
> -	if (validate_msg_fds(msg, 1) != 0)
> +	int expected_fds;
> +
> +	expected_fds = (msg->payload.u64 & VHOST_USER_VRING_NOFD_MASK) ? 0 : 1;
> +	if (validate_msg_fds(msg, expected_fds) != 0)
>  		return VH_RESULT_ERR;
>  
>  	if (!(msg->payload.u64 & VHOST_USER_VRING_NOFD_MASK))
> @@ -1283,8 +1288,10 @@ vhost_user_set_vring_kick(struct virtio_net **pdev, struct VhostUserMsg *msg,
>  	struct virtio_net *dev = *pdev;
>  	struct vhost_vring_file file;
>  	struct vhost_virtqueue *vq;
> +	int expected_fds;
>  
> -	if (validate_msg_fds(msg, 1) != 0)
> +	expected_fds = (msg->payload.u64 & VHOST_USER_VRING_NOFD_MASK) ? 0 : 1;
> +	if (validate_msg_fds(msg, expected_fds) != 0)
>  		return VH_RESULT_ERR;
>  
>  	file.index = msg->payload.u64 & VHOST_USER_VRING_IDX_MASK;
> -- 
> 2.21.0
>