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

[Ilya Maximets <i.maximets@samsung.com>]

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.

> +				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
>