答复: [Samba] The memory maybe leak in samba 4.3.11

[Jeremy Allison]

On Tue, May 09, 2017 at 02:59:51AM +0000, Zhangxiaoxu via samba-technical wrote:
> Hi,
> Thanks a lot.
> 
> Use the valgrind, we found the stack of the malloc as below, so, maybe it is not memory leak.
>     ==2796353== 36,334,440 bytes in 100,929 blocks are still reachable in loss record 774 of 774
>     ==2796353==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
>     ==2796353==    by 0x953B88F: ??? (in /usr/lib/x86_64-linux-gnu/samba/libmessages-dgm.so.0)
>     ==2796353==    by 0x953BCA0: ??? (in /usr/lib/x86_64-linux-gnu/samba/libmessages-dgm.so.0)
>     ==2796353==    by 0x953C342: unix_msg_send (in /usr/lib/x86_64-linux-gnu/samba/libmessages-dgm.so.0)
>     ==2796353==    by 0x953E3B6: messaging_dgm_send (in /usr/lib/x86_64-linux-gnu/samba/libmessages-dgm.so.0)
>     ==2796353==    by 0x71732FF: messaging_send_iov_from (in /usr/lib/x86_64-linux-gnu/libsmbconf.so.0)
>     ==2796353==    by 0x716E1BA: ??? (in /usr/lib/x86_64-linux-gnu/libsmbconf.so.0)
>     ==2796353==    by 0x716E869: ??? (in /usr/lib/x86_64-linux-gnu/libsmbconf.so.0)
>     ==2796353==    by 0x716EA91: ??? (in /usr/lib/x86_64-linux-gnu/libsmbconf.so.0)
>     ==2796353==    by 0x7171207: ctdbd_migrate (in /usr/lib/x86_64-linux-gnu/libsmbconf.so.0)
>     ==2796353==    by 0x716BD6E: ??? (in /usr/lib/x86_64-linux-gnu/libsmbconf.so.0)
>         ==2796353==    by 0xAE6692F: ??? (in /usr/lib/x86_64-linux-gnu/samba/libdbwrap.so.0)
> 
> Ifound the sendmsg is always failed because erron=EINTR, but smbd also need to malloc for the new msgs, so the res of the smbd grows up quickly.
> 
> I add some code in unix_dgram_send_job, just send 10 times if sendmsg faild with EINTR, the res will not grows up anymore.
> Another, keep the max queue length to 100 also work well.
> 
> I don’t know whether it is suitable for the process, also, I want to know why sendmsg return EINTR.

EINTR always means a signal was received and interrupted the send.

You're using 4.3.x yes ? In that branch:

static void unix_dgram_send_job(void *private_data)
{
        struct unix_dgram_msg *dmsg = private_data;

        do {
                struct msghdr_buf *hdr = unix_dgram_msghdr(dmsg);
                struct msghdr *msg = msghdr_buf_msghdr(hdr);
                dmsg->sent = sendmsg(dmsg->sock, msg, 0);
        } while ((dmsg->sent == -1) && (errno == EINTR));

        if (dmsg->sent == -1) {
                dmsg->sys_errno = errno;
        }
}

we already loop on EINTR. What exact version are you using and
what code did you add ?