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 10/12/2018 10:43 AM, Maxime Coquelin wrote:
> 
> 
> 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_CTRUNC.
s/remove/rework/

> 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
>>>