Re: [dpdk-dev] [PATCH v6 07/19] vhost: add number of fds to vhost-user messages and use it

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

On 10/11/2018 05:59 PM, Ilya Maximets wrote:
> On 11.10.2018 12:24, Maxime Coquelin wrote:
>> As soon as some ancillary data (fds) are received, it is copied
>> without checking its length.
>>
>> This patch adds the number of fds received to the message,
>> which is set in read_vhost_message().
>>
>> This is preliminary work to support sending fds to Qemu.
>>
>> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
>> ---
>>   lib/librte_vhost/socket.c     | 25 ++++++++++++++++++++-----
>>   lib/librte_vhost/vhost_user.c |  2 +-
>>   lib/librte_vhost/vhost_user.h |  4 +++-
>>   3 files changed, 24 insertions(+), 7 deletions(-)
>>
>> diff --git a/lib/librte_vhost/socket.c b/lib/librte_vhost/socket.c
>> index d63031747..3b0287a26 100644
>> --- a/lib/librte_vhost/socket.c
>> +++ b/lib/librte_vhost/socket.c
>> @@ -94,18 +94,24 @@ static struct vhost_user vhost_user = {
>>   	.mutex = PTHREAD_MUTEX_INITIALIZER,
>>   };
>>   
>> -/* return bytes# of read on success or negative val on failure. */
>> +/*
>> + * return bytes# of read on success or negative val on failure. Update fdnum
>> + * with number of fds read.
>> + */
>>   int
>> -read_fd_message(int sockfd, char *buf, int buflen, int *fds, int fd_num)
>> +read_fd_message(int sockfd, char *buf, int buflen, int *fds, int max_fds,
>> +		int *fd_num)
>>   {
>>   	struct iovec iov;
>>   	struct msghdr msgh;
>> -	size_t fdsize = fd_num * sizeof(int);
>> -	char control[CMSG_SPACE(fdsize)];
>> +	char control[CMSG_SPACE(max_fds * sizeof(int))];
>>   	struct cmsghdr *cmsg;
>>   	int got_fds = 0;
>> +	int *tmp_fds;
>>   	int ret;
>>   
>> +	*fd_num = 0;
>> +
>>   	memset(&msgh, 0, sizeof(msgh));
>>   	iov.iov_base = buf;
>>   	iov.iov_len  = buflen;
>> @@ -131,13 +137,22 @@ read_fd_message(int sockfd, char *buf, int buflen, int *fds, int fd_num)
>>   		if ((cmsg->cmsg_level == SOL_SOCKET) &&
>>   			(cmsg->cmsg_type == SCM_RIGHTS)) {
>>   			got_fds = (cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int);
>> +			if (got_fds > max_fds) {
> 
> Hmm. I just noticed that 'msg_controllen' is set to receive
> not more than max_fds descriptors. So, this case should not
> be possible. We will receive MSG_CTRUNC and return before
> the loop.

Maybe it is better to remove check for MSG_CTRUN.
IIUC, if MSG_CTRUNC happens, we may have to close anyway the ones
received.

Do you agree?

>> +				RTE_LOG(ERR, VHOST_CONFIG,
>> +					"Received msg contains more fds than supported\n");
>> +				tmp_fds = (int *)CMSG_DATA(cmsg);
>> +				while (got_fds--)
>> +					close(tmp_fds[got_fds]);
>> +				return -1;
>> +			}
>> +			*fd_num = got_fds;
>>   			memcpy(fds, CMSG_DATA(cmsg), got_fds * sizeof(int));
>>   			break;
>>   		}
>>   	}
>>   
>>   	/* Clear out unused file descriptors */
>> -	while (got_fds < fd_num)
>> +	while (got_fds < max_fds)
>>   		fds[got_fds++] = -1;
>>   
>>   	return ret;
>> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
>> index 83d3e6321..c1c5f35ff 100644
>> --- a/lib/librte_vhost/vhost_user.c
>> +++ b/lib/librte_vhost/vhost_user.c
>> @@ -1509,7 +1509,7 @@ read_vhost_message(int sockfd, struct VhostUserMsg *msg)
>>   	int ret;
>>   
>>   	ret = read_fd_message(sockfd, (char *)msg, VHOST_USER_HDR_SIZE,
>> -		msg->fds, VHOST_MEMORY_MAX_NREGIONS);
>> +		msg->fds, VHOST_MEMORY_MAX_NREGIONS, &msg->fd_num);
>>   	if (ret <= 0)
>>   		return ret;
>>   
>> diff --git a/lib/librte_vhost/vhost_user.h b/lib/librte_vhost/vhost_user.h
>> index 62654f736..9a91d496b 100644
>> --- a/lib/librte_vhost/vhost_user.h
>> +++ b/lib/librte_vhost/vhost_user.h
>> @@ -132,6 +132,7 @@ typedef struct VhostUserMsg {
>>   		VhostUserVringArea area;
>>   	} payload;
>>   	int fds[VHOST_MEMORY_MAX_NREGIONS];
>> +	int fd_num;
>>   } __attribute((packed)) VhostUserMsg;
>>   
>>   #define VHOST_USER_HDR_SIZE offsetof(VhostUserMsg, payload.u64)
>> @@ -155,7 +156,8 @@ int vhost_user_iotlb_miss(struct virtio_net *dev, uint64_t iova, uint8_t perm);
>>   int vhost_user_host_notifier_ctrl(int vid, bool enable);
>>   
>>   /* socket.c */
>> -int read_fd_message(int sockfd, char *buf, int buflen, int *fds, int fd_num);
>> +int read_fd_message(int sockfd, char *buf, int buflen, int *fds, int max_fds,
>> +		int *fd_num);
>>   int send_fd_message(int sockfd, char *buf, int buflen, int *fds, int fd_num);
>>   
>>   #endif
>>