syzkaller-repros/linux/7280eef4f9267125da5e9bd0c1969be57e1ce048.c

// DATA RACE in proc.forEachMountSource
// https://syzkaller.appspot.com/bug?id=7280eef4f9267125da5e9bd0c1969be57e1ce048
// status:fixed
// autogenerated by syzkaller (http://github.com/google/syzkaller)

#define _GNU_SOURCE
#include <endian.h>
#include <fcntl.h>
#include <linux/futex.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/syscall.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 <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 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 uintptr_t syz_open_procfs(uintptr_t a0, uintptr_t a1)
{

  char buf[128];
  memset(buf, 0, sizeof(buf));
  if (a0 == 0) {
    snprintf(buf, sizeof(buf), "/proc/self/%s", (char*)a1);
  } else if (a0 == (uintptr_t)-1) {
    snprintf(buf, sizeof(buf), "/proc/thread-self/%s", (char*)a1);
  } else {
    snprintf(buf, sizeof(buf), "/proc/self/task/%d/%s", (int)a0, (char*)a1);
  }
  int fd = open(buf, O_RDWR);
  if (fd == -1)
    fd = open(buf, O_RDONLY);
  return fd;
}

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 (running)
          usleep((call == num_calls - 1) ? 10000 : 1000);
        break;
      }
    }
  }
}

uint64_t r[1] = {0xffffffffffffffff};
void execute_call(int call)
{
  long res;
  switch (call) {
  case 0:
    memcpy((void*)0x20000180, "mountinfo", 10);
    res = syz_open_procfs(0, 0x20000180);
    if (res != -1)
      r[0] = res;
    break;
  case 1:
    memcpy((void*)0x20fd5ff8, "./file0", 8);
    syscall(__NR_mkdir, 0x20fd5ff8, 0);
    break;
  case 2:
    memcpy((void*)0x2000a000, "./file0", 8);
    memcpy((void*)0x20026ff8, "./file0", 8);
    memcpy((void*)0x200001c0, "ramfs", 6);
    syscall(__NR_mount, 0x2000a000, 0x20026ff8, 0x200001c0, 0x17, 0x200000c0);
    break;
  case 3:
    memcpy((void*)0x20d04000, "./file0", 8);
    memcpy((void*)0x20903000, "./file0", 8);
    memcpy((void*)0x20000340, "bdev", 5);
    syscall(__NR_mount, 0x20d04000, 0x20903000, 0x20000340, 0x100000,
            0x200002c0);
    break;
  case 4:
    memcpy((void*)0x20000240, "./file0", 8);
    memcpy((void*)0x20000000, ".", 1);
    memcpy((void*)0x20000040, "\x04\x5b\x89\x8f\x73", 5);
    syscall(__NR_mount, 0x20000240, 0x20000000, 0x20000040, 0x5004, 0);
    break;
  case 5:
    memcpy((void*)0x200008c0, ".", 1);
    memcpy((void*)0x20000080, ".", 1);
    memcpy((void*)0x20753000, "mslos", 6);
    syscall(__NR_mount, 0x200008c0, 0x20000080, 0x20753000, 0x5010, 0x20000ac0);
    break;
  case 6:
    memcpy((void*)0x20377ff8, ".", 1);
    memcpy((void*)0x20187ff8, ".", 1);
    memcpy((void*)0x20753000, "mslos", 6);
    syscall(__NR_mount, 0x20377ff8, 0x20187ff8, 0x20753000, 0x5010, 0x200e7000);
    break;
  case 7:
    *(uint64_t*)0x200023c0 = 0x200012c0;
    *(uint64_t*)0x200023c8 = 0x1000;
    syscall(__NR_preadv, r[0], 0x200023c0, 0x1000000000000205, 0);
    break;
  }
}

void loop()
{
  execute(8);
  collide = 1;
  execute(8);
}

int main()
{
  syscall(__NR_mmap, 0x20000000, 0x1000000, 3, 0x32, -1, 0);
  use_temporary_dir();
  loop();
  return 0;
}