[RTnet-developers] Problem accessing msg_name in rt_udp_recvmsg

[Manuel H. <man...@gm...>]

Hey, I'm sorry if it's false alarm, but Jan pointed out that the
implementation of rt_udp_recvmsg regarding msg_namelen seems wrong. So
I compared the piece of code to Linux and tried to figure out, how it
should be handled... I starred at it for quite a while but I don't get
this part:

    0393     struct sockaddr_in  *sin;

    0419     sin = msg->msg_name;
    0420
    0421     /* copy the address */
    0422     msg->msg_namelen = sizeof(*sin);
    0423     if (sin) {
    0424         sin->sin_family      = AF_INET;
    0425         sin->sin_port        = uh->source;
    0426         sin->sin_addr.s_addr = skb->nh.iph->saddr;
    0427     }

Isn't msg->msg_name a user space buffer? Why is it possible to access
it from kernel space (Line 424 - 426)? I'm not really familiar with
the Linux kernel that much, therefore I checked some other parts of
RTnet (ipv4/tcp/tcp.c) and there is something strange as well:

    2053     len = msg->msg_iov[0].iov_len;
    2054     buf = msg->msg_iov[0].iov_base;

So I'm really getting confused... I mean wouldn't such a bug cause
serious problems? I'm running RTnet since months using the recvmsg
system call (udp) all the time and never encountered a problem. Sorry
ifthis question is somehow stupid, I really tried to figure it out
myself...