syzkaller-repros/linux/26b6cfa3b92fa8cf9ae095c108a988e73dbafab8.c

// KASAN: null-ptr-deref Read in refcount_sub_and_test
// https://syzkaller.appspot.com/bug?id=26b6cfa3b92fa8cf9ae095c108a988e73dbafab8
// status:fixed
// autogenerated by syzkaller (http://github.com/google/syzkaller)

#define _GNU_SOURCE
#include <endian.h>
#include <errno.h>
#include <errno.h>
#include <fcntl.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdio.h>
#include <sys/stat.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.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 <string.h>

const int kFailStatus = 67;
const int kRetryStatus = 69;

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 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 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;
}

uint64_t r[1] = {0xffffffffffffffff};
void loop()
{
  long res = 0;
  res = syscall(__NR_socket, 0x10, 3, 0);
  if (res != -1)
    r[0] = res;
  *(uint64_t*)0x20002fc8 = 0x20000000;
  *(uint16_t*)0x20000000 = 0x10;
  *(uint16_t*)0x20000002 = 0xf000;
  *(uint32_t*)0x20000004 = 0;
  *(uint32_t*)0x20000008 = 0;
  *(uint32_t*)0x20002fd0 = 0x80;
  *(uint64_t*)0x20002fd8 = 0x200001c0;
  *(uint64_t*)0x200001c0 = 0x20000080;
  memcpy((void*)0x20000080,
         "\x55\x00\x00\x00\x18\x00\x7f\xbd\xb7\x2d\x1c\xb2\xa4\xa2\x80\x93\x0a"
         "\x06\x80\xfe\x00\xa8\x43\x08\x91\x00\x00\x00\x39\x00\x08\x00\x0a\x00"
         "\x05\x00\x00\x00\x00\x00\x19\x00\xa3\x07\x25\x00\x00\x00\x00\x00\xd3"
         "\x74\xe1\xb6\x1e\x32\xab\xd0\xa4\xdf\x57\xdb\x81\x31\x4c\x00\xdc\x13"
         "\x38\xd5\x44\x00\x00\x9b\x84\x13\x6e\xf7\x5a\xfb\x83\xde\x44\x8d\xaa",
         85);
  *(uint64_t*)0x200001c8 = 0x55;
  *(uint64_t*)0x20002fe0 = 1;
  *(uint64_t*)0x20002fe8 = 0x20006000;
  *(uint64_t*)0x20002ff0 = 0;
  *(uint32_t*)0x20002ff8 = 0;
  write_file("/sys/kernel/debug/failslab/ignore-gfp-wait", "N");
  write_file("/sys/kernel/debug/fail_futex/ignore-private", "N");
  inject_fault(3);
  syscall(__NR_sendmsg, r[0], 0x20002fc8, 0);
}

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