Re: [dpdk-stable] [17.11 LTS PATCH] vhost: fix vring requests validation broken if no FD

[Tiwei Bie <tiwei.bie@intel.com>]

On Thu, Nov 14, 2019 at 04:16:15PM +0100, Maxime Coquelin wrote:
> From: Zhike Wang <wangzk320@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: 1f6147d9a01f ("vhost: fix possible denial of service by leaking FDs")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Zhike Wang <wangzk320@163.com>
> Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
> 
> Backport not tested yet.
> 
>  lib/librte_vhost/vhost_user.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
> index d4643dc350..0f8e0df8c7 100644
> --- a/lib/librte_vhost/vhost_user.c
> +++ b/lib/librte_vhost/vhost_user.c
> @@ -1409,6 +1409,7 @@ vhost_user_msg_handler(int vid, int fd)
>  	struct VhostUserMsg msg;
>  	int ret;
>  	int unlock_required = 0;
> +	int expected_fds;
>  
>  	dev = get_device(vid);
>  	if (dev == NULL)
> @@ -1586,12 +1587,16 @@ vhost_user_msg_handler(int vid, int fd)
>  		break;
>  
>  	case VHOST_USER_SET_VRING_KICK:
> -		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 -1;
>  
>  		vhost_user_set_vring_kick(&dev, &msg);
>  		break;
>  	case VHOST_USER_SET_VRING_CALL:
> +		expected_fds =
> +			(msg.payload.u64 & VHOST_USER_VRING_NOFD_MASK) ? 0 : 1;
>  		if (validate_msg_fds(&msg, 1) != 0)

Typo, s/1/expected_fds/

>  			return -1;
>  
> @@ -1599,6 +1604,8 @@ vhost_user_msg_handler(int vid, int fd)
>  		break;
>  
>  	case VHOST_USER_SET_VRING_ERR:
> +		expected_fds =
> +			(msg.payload.u64 & VHOST_USER_VRING_NOFD_MASK) ? 0 : 1;
>  		if (validate_msg_fds(&msg, 1) != 0)

Ditto.

Thanks,
Tiwei

>  			return -1;
>  
> -- 
> 2.21.0
>