[Bug] WARNING: ODEBUG bug in __mcheck_cpu_init_timer

[Sam Sun]

Dear developers and maintainers,

We encountered a kernel warning with our modified Syzkaller. It is
tested on kernel 6.8.0-rc7. C repro and kernel config are attached to
this email. Bug report is listed below.

```
ODEBUG: init active (active state 0) object: ffff888063a28000 object
type: timer_list hint: mce_timer_fn+0x0/0x240
arch/x86/kernel/cpu/mce/core.c:2642
WARNING: CPU: 0 PID: 8120 at lib/debugobjects.c:514
debug_print_object+0x1a0/0x2a0 lib/debugobjects.c:514
Modules linked in:
CPU: 0 PID: 8120 Comm: syz-executor447 Not tainted 6.7.0-rc7 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
RIP: 0010:debug_print_object+0x1a0/0x2a0 lib/debugobjects.c:514
Code: fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 75 4c 48 8b 14 dd a0
aa 10 8b 41 56 4c 89 e6 48 c7 c7 a0 9d 10 8b e8 81 32 ef fc 90 <0f> 0b
90 90 58 83 05 28 9a bd 0a 01 48 83 c4 18 5b 5d 41 5c 41 5d
RSP: 0018:ffffc90002aef9a0 EFLAGS: 00010082
RAX: 0000000000000000 RBX: 0000000000000003 RCX: ffffffff814c00fa
RDX: ffff888108431940 RSI: ffffffff814c0107 RDI: 0000000000000001
RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffffffff8b10a380
R13: ffffffff8aaf6240 R14: ffffffff81334bf0 R15: ffff88801305ada8
FS:  000055555673c3c0(0000) GS:ffff888063a00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000080 CR3: 000000010635d000 CR4: 0000000000750ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
 <TASK>
 __debug_object_init+0x1cb/0x2a0 lib/debugobjects.c:651
 debug_timer_init kernel/time/timer.c:777 [inline]
 debug_init kernel/time/timer.c:825 [inline]
 init_timer_key+0x31/0x1e0 kernel/time/timer.c:869
 __mcheck_cpu_init_timer+0x70/0xf0 arch/x86/kernel/cpu/mce/core.c:2074
 mce_cpu_restart arch/x86/kernel/cpu/mce/core.c:2373 [inline]
 mce_cpu_restart+0x96/0xb0 arch/x86/kernel/cpu/mce/core.c:2367
 csd_do_func kernel/smp.c:133 [inline]
 smp_call_function_many_cond+0x121f/0x1570 kernel/smp.c:846
 on_each_cpu_cond_mask+0x40/0x90 kernel/smp.c:1023
 on_each_cpu include/linux/smp.h:71 [inline]
 mce_restart arch/x86/kernel/cpu/mce/core.c:2380 [inline]
 set_bank+0x22a/0x370 arch/x86/kernel/cpu/mce/core.c:2450
 dev_attr_store+0x54/0x80 drivers/base/core.c:2366
 sysfs_kf_write+0x114/0x170 fs/sysfs/file.c:136
 kernfs_fop_write_iter+0x337/0x500 fs/kernfs/file.c:334
 call_write_iter include/linux/fs.h:2020 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x96a/0xd80 fs/read_write.c:584
 ksys_write+0x122/0x250 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x40/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7f2d0b70277d
Code: c3 e8 a7 1f 00 00 0f 1f 80 00 00 00 00 f3 0f 1e fa 48 89 f8 48
89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d
01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe0266ce18 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000000000000003e RCX: 00007f2d0b70277d
RDX: 0000000000000002 RSI: 00000000200000c0 RDI: 0000000000000003
RBP: 00000000000f4240 R08: 00007f2d0b757b75 R09: 00007f2d0b757b75
R10: 00007f2d0b757b75 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffe0266d078 R14: 00007ffe0266ce40 R15: 00007ffe0266ce30
 </TASK>
```

It seems that when restarting MCE the timer has been initialized
already. If you have any questions, please contact us.

Reported by: Yue Sun <samsun1006219@xxxxxxxxx>
Reported by: xingwei lee <xrivendell7@xxxxxxxxx>

Best Regards,
Yue

Attachment: config
Description: Binary data

// 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/prctl.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <time.h>
#include <unistd.h>

static 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 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 kill_and_wait(int pid, int* status)
{
  kill(-pid, SIGKILL);
  kill(pid, SIGKILL);
  for (int 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 = 0;
  for (;; iter++) {
    int pid = fork();
    if (pid < 0)
      exit(1);
    if (pid == 0) {
      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 < 5000)
        continue;
      kill_and_wait(pid, &status);
      break;
    }
  }
}

uint64_t r[1] = {0xffffffffffffffff};

void execute_one(void)
{
  intptr_t res = 0;
  memcpy((void*)0x20000080,
         "/sys/devices/system/machinecheck/machinecheck0/bank0\000", 53);
  res = syscall(__NR_openat, /*fd=*/0xffffffffffffff9cul, /*file=*/0x20000080ul,
                /*flags=*/1ul, /*mode=*/0ul);
  if (res != -1)
    r[0] = res;
  memcpy((void*)0x200000c0, "0\000", 2);
  syscall(__NR_write, /*fd=*/r[0], /*val=*/0x200000c0ul, /*len=*/2ul);
  {
    int i;
    for (i = 0; i < 64; i++) {
      syscall(__NR_write, /*fd=*/r[0], /*val=*/0x200000c0ul, /*len=*/2ul);
    }
  }
}
int main(void)
{
  syscall(__NR_mmap, /*addr=*/0x1ffff000ul, /*len=*/0x1000ul, /*prot=*/0ul,
          /*flags=*/0x32ul, /*fd=*/-1, /*offset=*/0ul);
  syscall(__NR_mmap, /*addr=*/0x20000000ul, /*len=*/0x1000000ul, /*prot=*/7ul,
          /*flags=*/0x32ul, /*fd=*/-1, /*offset=*/0ul);
  syscall(__NR_mmap, /*addr=*/0x21000000ul, /*len=*/0x1000ul, /*prot=*/0ul,
          /*flags=*/0x32ul, /*fd=*/-1, /*offset=*/0ul);
  for (procid = 0; procid < 4; procid++) {
    if (fork() == 0) {
      loop();
    }
  }
  sleep(1000000);
  return 0;
}