syzkaller-repros/linux/1b8def838c616fcdf45f6a52434b9b089a743e2b.c

// BUG: unable to handle kernel NULL pointer dereference in l2tp_session_create
// https://syzkaller.appspot.com/bug?id=1b8def838c616fcdf45f6a52434b9b089a743e2b
// status:open
// autogenerated by syzkaller (http://github.com/google/syzkaller)

#define _GNU_SOURCE
#include <endian.h>
#include <errno.h>
#include <linux/futex.h>
#include <pthread.h>
#include <signal.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/prctl.h>
#include <sys/syscall.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <time.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 <string.h>
#include <string.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 __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 uint64_t current_time_ms()
{
  struct timespec ts;

  if (clock_gettime(CLOCK_MONOTONIC, &ts))
    fail("clock_gettime failed");
  return (uint64_t)ts.tv_sec * 1000 + (uint64_t)ts.tv_nsec / 1000000;
}

static void execute_one();
extern unsigned long long procid;

static void loop()
{
  int iter;
  for (iter = 0;; iter++) {
    int pid = fork();
    if (pid < 0)
      fail("clone failed");
    if (pid == 0) {
      prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
      setpgrp();
      execute_one();
      doexit(0);
    }

    int status = 0;
    uint64_t start = current_time_ms();
    for (;;) {
      int res = waitpid(-1, &status, __WALL | WNOHANG);
      if (res == pid) {
        break;
      }
      usleep(1000);
      if (current_time_ms() - start < 3 * 1000)
        continue;
      kill(-pid, SIGKILL);
      kill(pid, SIGKILL);
      while (waitpid(-1, &status, __WALL) != pid) {
      }
      break;
    }
  }
}

struct thread_t {
  int created, running, call;
  pthread_t th;
};

static struct thread_t threads[16];
static void execute_call(int call);
static int running;
static int collide;

static void* thr(void* arg)
{
  struct thread_t* th = (struct thread_t*)arg;
  for (;;) {
    while (!__atomic_load_n(&th->running, __ATOMIC_ACQUIRE))
      syscall(SYS_futex, &th->running, FUTEX_WAIT, 0, 0);
    execute_call(th->call);
    __atomic_fetch_sub(&running, 1, __ATOMIC_RELAXED);
    __atomic_store_n(&th->running, 0, __ATOMIC_RELEASE);
    syscall(SYS_futex, &th->running, FUTEX_WAKE);
  }
  return 0;
}

static void execute(int num_calls)
{
  int call, thread;
  running = 0;
  for (call = 0; call < num_calls; call++) {
    for (thread = 0; thread < sizeof(threads) / sizeof(threads[0]); thread++) {
      struct thread_t* th = &threads[thread];
      if (!th->created) {
        th->created = 1;
        pthread_attr_t attr;
        pthread_attr_init(&attr);
        pthread_attr_setstacksize(&attr, 128 << 10);
        pthread_create(&th->th, &attr, thr, th);
      }
      if (!__atomic_load_n(&th->running, __ATOMIC_ACQUIRE)) {
        th->call = call;
        __atomic_fetch_add(&running, 1, __ATOMIC_RELAXED);
        __atomic_store_n(&th->running, 1, __ATOMIC_RELEASE);
        syscall(SYS_futex, &th->running, FUTEX_WAKE);
        if (collide && call % 2)
          break;
        struct timespec ts;
        ts.tv_sec = 0;
        ts.tv_nsec = 20 * 1000 * 1000;
        syscall(SYS_futex, &th->running, FUTEX_WAIT, 1, &ts);
        if (__atomic_load_n(&running, __ATOMIC_RELAXED))
          usleep((call == num_calls - 1) ? 10000 : 1000);
        break;
      }
    }
  }
}

uint64_t r[3] = {0xffffffffffffffff, 0xffffffffffffffff, 0xffffffffffffffff};
unsigned long long procid;
void execute_call(int call)
{
  long res;
  switch (call) {
  case 0:
    res = syscall(__NR_socket, 0xa, 2, 0);
    if (res != -1)
      r[0] = res;
    break;
  case 1:
    res = syscall(__NR_socket, 0x18, 1, 1);
    if (res != -1)
      r[1] = res;
    break;
  case 2:
    NONFAILING(*(uint32_t*)0x20000000 = 1);
    NONFAILING(*(uint32_t*)0x20000004 = 6);
    NONFAILING(*(uint32_t*)0x20000008 = 9);
    NONFAILING(*(uint32_t*)0x2000000c = 5);
    syscall(__NR_setsockopt, r[0], 0x10e, 7, 0x20000000, 0x10);
    break;
  case 3:
    NONFAILING(*(uint16_t*)0x205fafd2 = 0x18);
    NONFAILING(*(uint32_t*)0x205fafd4 = 1);
    NONFAILING(*(uint32_t*)0x205fafd8 = 0);
    NONFAILING(*(uint32_t*)0x205fafdc = r[0]);
    NONFAILING(*(uint16_t*)0x205fafe0 = 2);
    NONFAILING(*(uint16_t*)0x205fafe2 = htobe16(0));
    NONFAILING(*(uint32_t*)0x205fafe4 = htobe32(0xe0000002));
    NONFAILING(*(uint8_t*)0x205fafe8 = 0);
    NONFAILING(*(uint8_t*)0x205fafe9 = 0);
    NONFAILING(*(uint8_t*)0x205fafea = 0);
    NONFAILING(*(uint8_t*)0x205fafeb = 0);
    NONFAILING(*(uint8_t*)0x205fafec = 0);
    NONFAILING(*(uint8_t*)0x205fafed = 0);
    NONFAILING(*(uint8_t*)0x205fafee = 0);
    NONFAILING(*(uint8_t*)0x205fafef = 0);
    NONFAILING(*(uint32_t*)0x205faff0 = 4);
    NONFAILING(*(uint32_t*)0x205faff4 = 0);
    NONFAILING(*(uint32_t*)0x205faff8 = 0);
    NONFAILING(*(uint32_t*)0x205faffc = 0);
    syscall(__NR_connect, r[1], 0x205fafd2, 0x2e);
    break;
  case 4:
    res = syscall(__NR_socket, 0x10, 3, 0xa);
    if (res != -1)
      r[2] = res;
    break;
  case 5:
    syscall(__NR_dup3, r[2], r[1], 0x80000);
    break;
  case 6:
    syscall(__NR_dup3, r[1], r[0], 0x80000);
    break;
  }
}

void execute_one()
{
  execute(7);
  collide = 1;
  execute(7);
}

int main()
{
  syscall(__NR_mmap, 0x20000000, 0x1000000, 3, 0x32, -1, 0);
  for (procid = 0; procid < 8; procid++) {
    if (fork() == 0) {
      install_segv_handler();
      for (;;) {
        loop();
      }
    }
  }
  sleep(1000000);
  return 0;
}