Re: kernel BUG at net/rxrpc/local_object.c:LINE!

David Howells
2019-07-02T13:37:39Z

syzbot <syzbot+1e0edc4b8b7494c28450@syzkaller.appspotmail.com> wrote:

I *think* the reproducer boils down to the attached, but I can't get syzkaller
to work and the attached sample does not cause the oops to occur. Can you try
it in your environment?

> The bug was bisected to:
>
> commit 46894a13599a977ac35411b536fb3e0b2feefa95
> Author: David Howells <dhowells@redhat.com>
> Date: Thu Oct 4 08:32:28 2018 +0000
>
> rxrpc: Use IPv4 addresses throught the IPv6

This might not be the correct bisection point. If you look at the attached
sample, you're mixing AF_INET and AF_INET6. If you try AF_INET throughout,
that might get a different point. On the other hand, since you've bound the
socket, the AF_INET6 passed to socket() should be ignored.

David
---
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <linux/rxrpc.h>

static const unsigned char inet4_addr[4] = {
0xe0, 0x00, 0x00, 0x01
};

int main(void)
{
struct sockaddr_rxrpc srx;
int fd;

memset(&srx, 0, sizeof(srx));
srx.srx_family = AF_RXRPC;
srx.srx_service = 0;
srx.transport_type = AF_INET;
srx.transport_len = sizeof(srx.transport.sin);
srx.transport.sin.sin_family = AF_INET;
srx.transport.sin.sin_port = htons(0x4e21);
memcpy(&srx.transport.sin.sin_addr, inet4_addr, 4);

fd = socket(AF_RXRPC, SOCK_DGRAM, AF_INET6);
if (fd == -1) {
perror("socket");
exit(1);
}

if (bind(fd, (struct sockaddr *)&srx, sizeof(srx)) == -1) {
perror("bind");
exit(1);
}

sleep(20);

// Whilst sleeping, hit with:
// echo -e '\0\0\0\0\0\0\0\0' | ncat -4u --send-only 224.0.0.1 20001

return 0;
}