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

[Maxime Coquelin <maxime.coquelin@redhat.com>]

Thanks Tiwei!

Good catch, just posted the v2 for both 16.11 and 17.11.

Maxime
On 11/15/19 5:27 AM, Tiwei Bie wrote:
> 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
>>
>