Re: Crash with SO_REUSEPORT and ef456144da8ef507c8cf504284b6042e9201a05c

[Marc Dionne <marc.c.dionne@gmail.com>]

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On Tue, Jan 19, 2016 at 12:31 PM, Craig Gallek <kraig@google.com> wrote:
>
> I need to think about how to handle setsockopt-after-bind condition a
> bit more, but the NULL pointer dereference is obviously wrong.  Do you
> have a way to easily reproduce this?  I've only managed to get it to
> happen once so far...

The attached code reliably triggers the crash for me.

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#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>

#include <arpa/inet.h>

int
main(int argc, char **argv)
{
    struct sockaddr_in addr, addr2;
    int len, optval = 1;
    int s1, s2;

    addr.sin_addr.s_addr = htonl(INADDR_ANY);
    addr.sin_family = AF_INET;
    addr.sin_port = 0;

    s1 = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    s2 = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);

    bind(s1, (struct sockaddr *)&addr, sizeof(addr));
    setsockopt(s1, SOL_SOCKET, SO_REUSEPORT, &optval, sizeof(optval));
    setsockopt(s2, SOL_SOCKET, SO_REUSEPORT, &optval, sizeof(optval));

    len = sizeof(addr);
    getsockname(s1, (struct sockaddr *)&addr, (socklen_t *)&len);
    addr2.sin_addr.s_addr = htonl(INADDR_ANY);
    addr2.sin_family = AF_INET;
    addr2.sin_port = addr.sin_port;
    bind(s2, (struct sockaddr *)&addr2, sizeof(addr));
    close(s2);
    close(s1);
    return 0;
}