text: // INFO: rcu detected stall in ext4_file_write_iter
  // https://syzkaller.appspot.com/bug?id=997b03a7f1ed8c68a818f0a2aa9174205bf61954
  // status:open
  // autogenerated by syzkaller (https://github.com/google/syzkaller)
  
  #define _GNU_SOURCE
  
  #include <dirent.h>
  #include <endian.h>
  #include <errno.h>
  #include <fcntl.h>
  #include <signal.h>
  #include <stdarg.h>
  #include <stdbool.h>
  #include <stdint.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <sys/ioctl.h>
  #include <sys/mount.h>
  #include <sys/prctl.h>
  #include <sys/stat.h>
  #include <sys/syscall.h>
  #include <sys/types.h>
  #include <sys/wait.h>
  #include <time.h>
  #include <unistd.h>
  
  unsigned long long procid;
  
  static void sleep_ms(uint64_t ms)
  {
    usleep(ms * 1000);
  }
  
  static uint64_t current_time_ms(void)
  {
    struct timespec ts;
    if (clock_gettime(CLOCK_MONOTONIC, &ts))
      exit(1);
    return (uint64_t)ts.tv_sec * 1000 + (uint64_t)ts.tv_nsec / 1000000;
  }
  
  static void use_temporary_dir(void)
  {
    char tmpdir_template[] = "./syzkaller.XXXXXX";
    char* tmpdir = mkdtemp(tmpdir_template);
    if (!tmpdir)
      exit(1);
    if (chmod(tmpdir, 0777))
      exit(1);
    if (chdir(tmpdir))
      exit(1);
  }
  
  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;
  }
  
  #define FS_IOC_SETFLAGS _IOW('f', 2, long)
  static void remove_dir(const char* dir)
  {
    DIR* dp;
    struct dirent* ep;
    int iter = 0;
  retry:
    while (umount2(dir, MNT_DETACH) == 0) {
    }
    dp = opendir(dir);
    if (dp == NULL) {
      if (errno == EMFILE) {
        exit(1);
      }
      exit(1);
    }
    while ((ep = readdir(dp))) {
      if (strcmp(ep->d_name, ".") == 0 || strcmp(ep->d_name, "..") == 0)
        continue;
      char filename[FILENAME_MAX];
      snprintf(filename, sizeof(filename), "%s/%s", dir, ep->d_name);
      while (umount2(filename, MNT_DETACH) == 0) {
      }
      struct stat st;
      if (lstat(filename, &st))
        exit(1);
      if (S_ISDIR(st.st_mode)) {
        remove_dir(filename);
        continue;
      }
      int i;
      for (i = 0;; i++) {
        if (unlink(filename) == 0)
          break;
        if (errno == EPERM) {
          int fd = open(filename, O_RDONLY);
          if (fd != -1) {
            long flags = 0;
            if (ioctl(fd, FS_IOC_SETFLAGS, &flags) == 0)
              close(fd);
            continue;
          }
        }
        if (errno == EROFS) {
          break;
        }
        if (errno != EBUSY || i > 100)
          exit(1);
        if (umount2(filename, MNT_DETACH))
          exit(1);
      }
    }
    closedir(dp);
    int i;
    for (i = 0;; i++) {
      if (rmdir(dir) == 0)
        break;
      if (i < 100) {
        if (errno == EPERM) {
          int fd = open(dir, O_RDONLY);
          if (fd != -1) {
            long flags = 0;
            if (ioctl(fd, FS_IOC_SETFLAGS, &flags) == 0)
              close(fd);
            continue;
          }
        }
        if (errno == EROFS) {
          break;
        }
        if (errno == EBUSY) {
          if (umount2(dir, MNT_DETACH))
            exit(1);
          continue;
        }
        if (errno == ENOTEMPTY) {
          if (iter < 100) {
            iter++;
            goto retry;
          }
        }
      }
      exit(1);
    }
  }
  
  static void kill_and_wait(int pid, int* status)
  {
    kill(-pid, SIGKILL);
    kill(pid, SIGKILL);
    int i;
    for (i = 0; i < 100; i++) {
      if (waitpid(-1, status, WNOHANG | __WALL) == pid)
        return;
      usleep(1000);
    }
    DIR* dir = opendir("/sys/fs/fuse/connections");
    if (dir) {
      for (;;) {
        struct dirent* ent = readdir(dir);
        if (!ent)
          break;
        if (strcmp(ent->d_name, ".") == 0 || strcmp(ent->d_name, "..") == 0)
          continue;
        char abort[300];
        snprintf(abort, sizeof(abort), "/sys/fs/fuse/connections/%s/abort",
                 ent->d_name);
        int fd = open(abort, O_WRONLY);
        if (fd == -1) {
          continue;
        }
        if (write(fd, abort, 1) < 0) {
        }
        close(fd);
      }
      closedir(dir);
    } else {
    }
    while (waitpid(-1, status, __WALL) != pid) {
    }
  }
  
  static void setup_test()
  {
    prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
    setpgrp();
    write_file("/proc/self/oom_score_adj", "1000");
  }
  
  static void execute_one(void);
  
  #define WAIT_FLAGS __WALL
  
  static void loop(void)
  {
    int iter;
    for (iter = 0;; iter++) {
      char cwdbuf[32];
      sprintf(cwdbuf, "./%d", iter);
      if (mkdir(cwdbuf, 0777))
        exit(1);
      int pid = fork();
      if (pid < 0)
        exit(1);
      if (pid == 0) {
        if (chdir(cwdbuf))
          exit(1);
        setup_test();
        execute_one();
        exit(0);
      }
      int status = 0;
      uint64_t start = current_time_ms();
      for (;;) {
        if (waitpid(-1, &status, WNOHANG | WAIT_FLAGS) == pid)
          break;
        sleep_ms(1);
        if (current_time_ms() - start < 5 * 1000)
          continue;
        kill_and_wait(pid, &status);
        break;
      }
      remove_dir(cwdbuf);
    }
  }
  
  #ifndef __NR_sched_setattr
  #define __NR_sched_setattr 314
  #endif
  
  uint64_t r[1] = {0xffffffffffffffff};
  
  void execute_one(void)
  {
    intptr_t res = 0;
    *(uint32_t*)0x20000080 = 0;
    *(uint32_t*)0x20000084 = 6;
    *(uint64_t*)0x20000088 = 0;
    *(uint32_t*)0x20000090 = 0;
    *(uint32_t*)0x20000094 = 0;
    *(uint64_t*)0x20000098 = 0x8000000009917;
    *(uint64_t*)0x200000a0 = 0x400000000000fffd;
    *(uint64_t*)0x200000a8 = 0;
    syscall(__NR_sched_setattr, 0, 0x20000080, 0);
    memcpy((void*)0x20000080, "./bus\000", 6);
    res = syscall(__NR_open, 0x20000080, 0x1fe, 0);
    if (res != -1)
      r[0] = res;
    memcpy((void*)0x20000240, "\x9c\x54\xe7\x77\x25\x32\x3b\xe4\x8b\x2b\x58\x05"
                              "\xa7\x26\xde\x15\x4f\x38\x34\xdf\x22\x00\x08\xfb"
                              "\x9b\x15\x98\x52",
           28);
    syscall(__NR_write, r[0], 0x20000240, 0x1c);
    *(uint64_t*)0x20000000 = 0;
    syscall(__NR_sendfile, r[0], r[0], 0x20000000, 0x8080fffffffe);
  }
  int main(void)
  {
    syscall(__NR_mmap, 0x20000000, 0x1000000, 3, 0x32, -1, 0);
    for (procid = 0; procid < 6; procid++) {
      if (fork() == 0) {
        use_temporary_dir();
        loop();
      }
    }
    sleep(1000000);
    return 0;
  }
  