text: // BUG: unable to handle kernel NULL pointer dereference in __getblk_gfp
  // https://syzkaller.appspot.com/bug?id=12ac4258b0e6047f57dc5ca5aa9d1424201e598e
  // status:invalid
  // autogenerated by syzkaller (http://github.com/google/syzkaller)
  
  #define _GNU_SOURCE
  #include <arpa/inet.h>
  #include <endian.h>
  #include <errno.h>
  #include <fcntl.h>
  #include <linux/if.h>
  #include <linux/if_ether.h>
  #include <linux/if_tun.h>
  #include <linux/ip.h>
  #include <linux/tcp.h>
  #include <net/if_arp.h>
  #include <sched.h>
  #include <signal.h>
  #include <stdarg.h>
  #include <stdbool.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <sys/ioctl.h>
  #include <sys/prctl.h>
  #include <sys/resource.h>
  #include <sys/stat.h>
  #include <sys/syscall.h>
  #include <sys/time.h>
  #include <sys/types.h>
  #include <sys/uio.h>
  #include <sys/wait.h>
  #include <unistd.h>
  
  __attribute__((noreturn)) static void doexit(int status)
  {
    volatile unsigned i;
    syscall(__NR_exit_group, status);
    for (i = 0;; i++) {
    }
  }
  #include <errno.h>
  #include <setjmp.h>
  #include <signal.h>
  #include <stdarg.h>
  #include <stdint.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <sys/stat.h>
  
  const int kFailStatus = 67;
  const int kRetryStatus = 69;
  
  static void fail(const char* msg, ...)
  {
    int e = errno;
    va_list args;
    va_start(args, msg);
    vfprintf(stderr, msg, args);
    va_end(args);
    fprintf(stderr, " (errno %d)\n", e);
    doexit((e == ENOMEM || e == EAGAIN) ? kRetryStatus : kFailStatus);
  }
  
  static void exitf(const char* msg, ...)
  {
    int e = errno;
    va_list args;
    va_start(args, msg);
    vfprintf(stderr, msg, args);
    va_end(args);
    fprintf(stderr, " (errno %d)\n", e);
    doexit(kRetryStatus);
  }
  
  static __thread int skip_segv;
  static __thread jmp_buf segv_env;
  
  static void segv_handler(int sig, siginfo_t* info, void* uctx)
  {
    uintptr_t addr = (uintptr_t)info->si_addr;
    const uintptr_t prog_start = 1 << 20;
    const uintptr_t prog_end = 100 << 20;
    if (__atomic_load_n(&skip_segv, __ATOMIC_RELAXED) &&
        (addr < prog_start || addr > prog_end)) {
      _longjmp(segv_env, 1);
    }
    doexit(sig);
  }
  
  static void install_segv_handler()
  {
    struct sigaction sa;
  
    memset(&sa, 0, sizeof(sa));
    sa.sa_handler = SIG_IGN;
    syscall(SYS_rt_sigaction, 0x20, &sa, NULL, 8);
    syscall(SYS_rt_sigaction, 0x21, &sa, NULL, 8);
  
    memset(&sa, 0, sizeof(sa));
    sa.sa_sigaction = segv_handler;
    sa.sa_flags = SA_NODEFER | SA_SIGINFO;
    sigaction(SIGSEGV, &sa, NULL);
    sigaction(SIGBUS, &sa, NULL);
  }
  
  #define NONFAILING(...)                                                        \
    {                                                                            \
      __atomic_fetch_add(&skip_segv, 1, __ATOMIC_SEQ_CST);                       \
      if (_setjmp(segv_env) == 0) {                                              \
        __VA_ARGS__;                                                             \
      }                                                                          \
      __atomic_fetch_sub(&skip_segv, 1, __ATOMIC_SEQ_CST);                       \
    }
  
  static void use_temporary_dir()
  {
    char tmpdir_template[] = "./syzkaller.XXXXXX";
    char* tmpdir = mkdtemp(tmpdir_template);
    if (!tmpdir)
      fail("failed to mkdtemp");
    if (chmod(tmpdir, 0777))
      fail("failed to chmod");
    if (chdir(tmpdir))
      fail("failed to chdir");
  }
  
  static void vsnprintf_check(char* str, size_t size, const char* format,
                              va_list args)
  {
    int rv;
  
    rv = vsnprintf(str, size, format, args);
    if (rv < 0)
      fail("tun: snprintf failed");
    if ((size_t)rv >= size)
      fail("tun: string '%s...' doesn't fit into buffer", str);
  }
  
  static void snprintf_check(char* str, size_t size, const char* format, ...)
  {
    va_list args;
  
    va_start(args, format);
    vsnprintf_check(str, size, format, args);
    va_end(args);
  }
  
  #define COMMAND_MAX_LEN 128
  #define PATH_PREFIX                                                            \
    "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin "
  #define PATH_PREFIX_LEN (sizeof(PATH_PREFIX) - 1)
  
  static void execute_command(bool panic, const char* format, ...)
  {
    va_list args;
    char command[PATH_PREFIX_LEN + COMMAND_MAX_LEN];
    int rv;
  
    va_start(args, format);
    memcpy(command, PATH_PREFIX, PATH_PREFIX_LEN);
    vsnprintf_check(command + PATH_PREFIX_LEN, COMMAND_MAX_LEN, format, args);
    va_end(args);
    rv = system(command);
    if (rv) {
      if (panic)
        fail("command '%s' failed: %d", &command[0], rv);
    }
  }
  
  static int tunfd = -1;
  static int tun_frags_enabled;
  
  #define SYZ_TUN_MAX_PACKET_SIZE 1000
  
  #define TUN_IFACE "syz_tun"
  
  #define LOCAL_MAC "aa:aa:aa:aa:aa:aa"
  #define REMOTE_MAC "aa:aa:aa:aa:aa:bb"
  
  #define LOCAL_IPV4 "172.20.20.170"
  #define REMOTE_IPV4 "172.20.20.187"
  
  #define LOCAL_IPV6 "fe80::aa"
  #define REMOTE_IPV6 "fe80::bb"
  
  #define IFF_NAPI 0x0010
  #define IFF_NAPI_FRAGS 0x0020
  
  static void initialize_tun(void)
  {
    tunfd = open("/dev/net/tun", O_RDWR | O_NONBLOCK);
    if (tunfd == -1) {
      printf("tun: can't open /dev/net/tun: please enable CONFIG_TUN=y\n");
      printf("otherwise fuzzing or reproducing might not work as intended\n");
      return;
    }
    const int kTunFd = 252;
    if (dup2(tunfd, kTunFd) < 0)
      fail("dup2(tunfd, kTunFd) failed");
    close(tunfd);
    tunfd = kTunFd;
  
    struct ifreq ifr;
    memset(&ifr, 0, sizeof(ifr));
    strncpy(ifr.ifr_name, TUN_IFACE, IFNAMSIZ);
    ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_NAPI | IFF_NAPI_FRAGS;
    if (ioctl(tunfd, TUNSETIFF, (void*)&ifr) < 0) {
      ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
      if (ioctl(tunfd, TUNSETIFF, (void*)&ifr) < 0)
        fail("tun: ioctl(TUNSETIFF) failed");
    }
    if (ioctl(tunfd, TUNGETIFF, (void*)&ifr) < 0)
      fail("tun: ioctl(TUNGETIFF) failed");
    tun_frags_enabled = (ifr.ifr_flags & IFF_NAPI_FRAGS) != 0;
  
    execute_command(1, "sysctl -w net.ipv6.conf.%s.accept_dad=0", TUN_IFACE);
  
    execute_command(1, "sysctl -w net.ipv6.conf.%s.router_solicitations=0",
                    TUN_IFACE);
  
    execute_command(1, "ip link set dev %s address %s", TUN_IFACE, LOCAL_MAC);
    execute_command(1, "ip addr add %s/24 dev %s", LOCAL_IPV4, TUN_IFACE);
    execute_command(1, "ip -6 addr add %s/120 dev %s", LOCAL_IPV6, TUN_IFACE);
    execute_command(1, "ip neigh add %s lladdr %s dev %s nud permanent",
                    REMOTE_IPV4, REMOTE_MAC, TUN_IFACE);
    execute_command(1, "ip -6 neigh add %s lladdr %s dev %s nud permanent",
                    REMOTE_IPV6, REMOTE_MAC, TUN_IFACE);
    execute_command(1, "ip link set dev %s up", TUN_IFACE);
  }
  
  #define DEV_IPV4 "172.20.20.%d"
  #define DEV_IPV6 "fe80::%02hx"
  #define DEV_MAC "aa:aa:aa:aa:aa:%02hx"
  
  static void initialize_netdevices(void)
  {
    unsigned i;
    const char* devtypes[] = {"ip6gretap", "bridge", "vcan", "bond", "team"};
    const char* devnames[] = {"lo",
                              "sit0",
                              "bridge0",
                              "vcan0",
                              "tunl0",
                              "gre0",
                              "gretap0",
                              "ip_vti0",
                              "ip6_vti0",
                              "ip6tnl0",
                              "ip6gre0",
                              "ip6gretap0",
                              "erspan0",
                              "bond0",
                              "veth0",
                              "veth1",
                              "team0",
                              "veth0_to_bridge",
                              "veth1_to_bridge",
                              "veth0_to_bond",
                              "veth1_to_bond",
                              "veth0_to_team",
                              "veth1_to_team"};
    const char* devmasters[] = {"bridge", "bond", "team"};
  
    for (i = 0; i < sizeof(devtypes) / (sizeof(devtypes[0])); i++)
      execute_command(0, "ip link add dev %s0 type %s", devtypes[i], devtypes[i]);
    execute_command(0, "ip link add type veth");
  
    for (i = 0; i < sizeof(devmasters) / (sizeof(devmasters[0])); i++) {
      execute_command(
          0, "ip link add name %s_slave_0 type veth peer name veth0_to_%s",
          devmasters[i], devmasters[i]);
      execute_command(
          0, "ip link add name %s_slave_1 type veth peer name veth1_to_%s",
          devmasters[i], devmasters[i]);
      execute_command(0, "ip link set %s_slave_0 master %s0", devmasters[i],
                      devmasters[i]);
      execute_command(0, "ip link set %s_slave_1 master %s0", devmasters[i],
                      devmasters[i]);
      execute_command(0, "ip link set veth0_to_%s up", devmasters[i]);
      execute_command(0, "ip link set veth1_to_%s up", devmasters[i]);
    }
    execute_command(0, "ip link set bridge_slave_0 up");
    execute_command(0, "ip link set bridge_slave_1 up");
  
    for (i = 0; i < sizeof(devnames) / (sizeof(devnames[0])); i++) {
      char addr[32];
      snprintf_check(addr, sizeof(addr), DEV_IPV4, i + 10);
      execute_command(0, "ip -4 addr add %s/24 dev %s", addr, devnames[i]);
      snprintf_check(addr, sizeof(addr), DEV_IPV6, i + 10);
      execute_command(0, "ip -6 addr add %s/120 dev %s", addr, devnames[i]);
      snprintf_check(addr, sizeof(addr), DEV_MAC, i + 10);
      execute_command(0, "ip link set dev %s address %s", devnames[i], addr);
      execute_command(0, "ip link set dev %s up", devnames[i]);
    }
  }
  
  static bool write_file(const char* file, const char* what, ...)
  {
    char buf[1024];
    va_list args;
    va_start(args, what);
    vsnprintf(buf, sizeof(buf), what, args);
    va_end(args);
    buf[sizeof(buf) - 1] = 0;
    int len = strlen(buf);
  
    int fd = open(file, O_WRONLY | O_CLOEXEC);
    if (fd == -1)
      return false;
    if (write(fd, buf, len) != len) {
      int err = errno;
      close(fd);
      errno = err;
      return false;
    }
    close(fd);
    return true;
  }
  
  static void loop();
  
  static void sandbox_common()
  {
    prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
    setpgrp();
    setsid();
  
    struct rlimit rlim;
    rlim.rlim_cur = rlim.rlim_max = 160 << 20;
    setrlimit(RLIMIT_AS, &rlim);
    rlim.rlim_cur = rlim.rlim_max = 8 << 20;
    setrlimit(RLIMIT_MEMLOCK, &rlim);
    rlim.rlim_cur = rlim.rlim_max = 136 << 20;
    setrlimit(RLIMIT_FSIZE, &rlim);
    rlim.rlim_cur = rlim.rlim_max = 1 << 20;
    setrlimit(RLIMIT_STACK, &rlim);
    rlim.rlim_cur = rlim.rlim_max = 0;
    setrlimit(RLIMIT_CORE, &rlim);
  
    if (unshare(CLONE_NEWNS)) {
    }
    if (unshare(CLONE_NEWIPC)) {
    }
    if (unshare(0x02000000)) {
    }
    if (unshare(CLONE_NEWUTS)) {
    }
    if (unshare(CLONE_SYSVSEM)) {
    }
  }
  
  static int do_sandbox_none(void)
  {
    if (unshare(CLONE_NEWPID)) {
    }
    int pid = fork();
    if (pid < 0)
      fail("sandbox fork failed");
    if (pid)
      return pid;
  
    sandbox_common();
    if (unshare(CLONE_NEWNET)) {
    }
    initialize_tun();
    initialize_netdevices();
  
    loop();
    doexit(1);
  }
  
  static int inject_fault(int nth)
  {
    int fd;
    char buf[16];
  
    fd = open("/proc/thread-self/fail-nth", O_RDWR);
    if (fd == -1)
      exitf("failed to open /proc/thread-self/fail-nth");
    sprintf(buf, "%d", nth + 1);
    if (write(fd, buf, strlen(buf)) != (ssize_t)strlen(buf))
      exitf("failed to write /proc/thread-self/fail-nth");
    return fd;
  }
  
  static void execute_one();
  extern unsigned long long procid;
  
  void loop()
  {
    while (1) {
      execute_one();
    }
  }
  
  uint64_t r[1] = {0xffffffffffffffff};
  void execute_one()
  {
    long res = 0;
    NONFAILING(memcpy((void*)0x20000000, "/selinux/enforce", 17));
    res = syscall(__NR_openat, 0xffffffffffffff9c, 0x20000000, 0x10f34d, 0);
    if (res != -1)
      r[0] = res;
    write_file("/sys/kernel/debug/failslab/ignore-gfp-wait", "N");
    write_file("/sys/kernel/debug/fail_futex/ignore-private", "N");
    inject_fault(24);
    syscall(__NR_fallocate, r[0], 1, 0xc4d9, 0x200000000);
  }
  
  int main()
  {
    syscall(__NR_mmap, 0x20000000, 0x1000000, 3, 0x32, -1, 0);
    install_segv_handler();
    char* cwd = get_current_dir_name();
    for (;;) {
      if (chdir(cwd))
        fail("failed to chdir");
      use_temporary_dir();
      int pid = do_sandbox_none();
      int status = 0;
      while (waitpid(pid, &status, __WALL) != pid) {
      }
    }
  }
  