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 12.10.2018 12:52, Maxime Coquelin wrote:
> 
> 
> On 10/12/2018 11:53 AM, Ilya Maximets wrote:
>> On 12.10.2018 11:57, Maxime Coquelin wrote:
>>>
>>>
>>> On 10/12/2018 10:45 AM, Maxime Coquelin wrote:
>>>>
>>>>
>>>> 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?
>>>
>>> So it seems that other use of MSG_CTRUNC in DPDK and QEMU does care
>>> to close the ones that would have been received and just return an
>>> error.
>>
>> Did you mean 'does not care'?
> 
> Yes, I meant "does not care", sorry.

ok.

> 
>> 'read_msg()' in lib/librte_eal/common/eal_common_proc.c just returns -1
>> and 'slave_read()' in hw/virtio/vhost-user.c does not close fds, because
>> 'fdsize' is not set at the time of checking the flag.
>>
>>>
>>> I propose to do the same for now, an remove the got_fds > max_fds part.

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
>>>>>>>
>>>
>>>
> 
>