INFO: task hung in io_uring_release

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: bed3c0d8 Merge tag 'for-5.2-rc5-tag' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1418bf0aa00000
kernel config: https://syzkaller.appspot.com/x/.config?x=28ec3437a5394ee0
dashboard link: https://syzkaller.appspot.com/bug?extid=94324416c485d422fe15
compiler: clang version 9.0.0 (/home/glider/llvm/clang
80fee25776c2fb61e74c1ecb1a523375c2500b69)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+943244...@syzkaller.appspotmail.com

INFO: task syz-executor.5:8634 blocked for more than 143 seconds.
Not tainted 5.2.0-rc5+ #3
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5 D25632 8634 8224 0x00004004
Call Trace:
context_switch kernel/sched/core.c:2818 [inline]
__schedule+0x658/0x9e0 kernel/sched/core.c:3445
schedule+0x131/0x1d0 kernel/sched/core.c:3509
schedule_timeout+0x9a/0x2b0 kernel/time/timer.c:1783
do_wait_for_common+0x35e/0x5a0 kernel/sched/completion.c:83
__wait_for_common kernel/sched/completion.c:104 [inline]
wait_for_common kernel/sched/completion.c:115 [inline]
wait_for_completion+0x47/0x60 kernel/sched/completion.c:136
kthread_stop+0xb4/0x150 kernel/kthread.c:559
io_sq_thread_stop fs/io_uring.c:2252 [inline]
io_finish_async fs/io_uring.c:2259 [inline]
io_ring_ctx_free fs/io_uring.c:2770 [inline]
io_ring_ctx_wait_and_kill+0x268/0x880 fs/io_uring.c:2834
io_uring_release+0x5d/0x70 fs/io_uring.c:2842
__fput+0x2e4/0x740 fs/file_table.c:280
____fput+0x15/0x20 fs/file_table.c:313
task_work_run+0x17e/0x1b0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:185 [inline]
exit_to_usermode_loop arch/x86/entry/common.c:168 [inline]
prepare_exit_to_usermode+0x402/0x4f0 arch/x86/entry/common.c:199
syscall_return_slowpath+0x110/0x440 arch/x86/entry/common.c:279
do_syscall_64+0x126/0x140 arch/x86/entry/common.c:304
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x412fb1
Code: 80 3b 7c 0f 84 c7 02 00 00 c7 85 d0 00 00 00 00 00 00 00 48 8b 05 cf
a6 24 00 49 8b 14 24 41 b9 cb 2a 44 00 48 89 ee 48 89 df <48> 85 c0 4c 0f
45 c8 45 31 c0 31 c9 e8 0e 5b 00 00 85 c0 41 89 c7
RSP: 002b:00007ffe7ee6a180 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000412fb1
RDX: 0000001b2d920000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 0000000000000001 R08: 00000000f3a3e1f8 R09: 00000000f3a3e1fc
R10: 00007ffe7ee6a260 R11: 0000000000000293 R12: 000000000075c9a0
R13: 000000000075c9a0 R14: 0000000000024c00 R15: 000000000075bf2c

Showing all locks held in the system:
1 lock held by khungtaskd/1043:
#0: 00000000ec789630 (rcu_read_lock){....}, at: rcu_lock_acquire+0x4/0x30
include/linux/rcupdate.h:207
1 lock held by rsyslogd/8054:
#0: 00000000a1730567 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x243/0x2e0
fs/file.c:801
2 locks held by getty/8167:
#0: 000000000d85b796 (&tty->ldisc_sem){++++}, at:
tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:272
#1: 000000006ecd2335 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x2ee/0x1c80 drivers/tty/n_tty.c:2156
2 locks held by getty/8168:
#0: 000000005c58bd1f (&tty->ldisc_sem){++++}, at:
tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:272
#1: 00000000158ead38 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x2ee/0x1c80 drivers/tty/n_tty.c:2156
2 locks held by getty/8169:
#0: 000000003d373884 (&tty->ldisc_sem){++++}, at:
tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:272
#1: 0000000026014169 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x2ee/0x1c80 drivers/tty/n_tty.c:2156
2 locks held by getty/8170:
#0: 00000000ba3eabbd (&tty->ldisc_sem){++++}, at:
tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:272
#1: 0000000003284ce2 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x2ee/0x1c80 drivers/tty/n_tty.c:2156
2 locks held by getty/8171:
#0: 000000009fcb2c0e (&tty->ldisc_sem){++++}, at:
tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:272
#1: 00000000ac5d0da7 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x2ee/0x1c80 drivers/tty/n_tty.c:2156
2 locks held by getty/8172:
#0: 000000003f4e772c (&tty->ldisc_sem){++++}, at:
tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:272
#1: 000000000c930b31 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x2ee/0x1c80 drivers/tty/n_tty.c:2156
2 locks held by getty/8173:
#0: 000000002a3615cf (&tty->ldisc_sem){++++}, at:
tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:272
#1: 00000000dd5c3618 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x2ee/0x1c80 drivers/tty/n_tty.c:2156

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 1043 Comm: khungtaskd Not tainted 5.2.0-rc5+ #3
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1d8/0x2f8 lib/dump_stack.c:113
nmi_cpu_backtrace+0x89/0x160 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x125/0x230 lib/nmi_backtrace.c:62
arch_trigger_cpumask_backtrace+0x10/0x20 arch/x86/kernel/apic/hw_nmi.c:38
trigger_all_cpu_backtrace+0x17/0x20 include/linux/nmi.h:146
check_hung_uninterruptible_tasks kernel/hung_task.c:205 [inline]
watchdog+0xbb9/0xbd0 kernel/hung_task.c:289
kthread+0x325/0x350 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 2546 Comm: kworker/u4:4 Not tainted 5.2.0-rc5+ #3
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: bat_events batadv_nc_worker
RIP: 0010:__read_once_size include/linux/compiler.h:194 [inline]
RIP: 0010:arch_atomic_read arch/x86/include/asm/atomic.h:31 [inline]
RIP: 0010:atomic_read include/asm-generic/atomic-instrumented.h:27 [inline]
RIP: 0010:rcu_dynticks_curr_cpu_in_eqs kernel/rcu/tree.c:292 [inline]
RIP: 0010:rcu_is_watching+0x62/0xa0 kernel/rcu/tree.c:872
Code: 4c 89 f7 e8 70 50 4c 00 48 c7 c3 b8 5f 03 00 49 03 1e 48 89 df be 04
00 00 00 e8 89 25 4c 00 48 89 d8 48 c1 e8 03 42 8a 04 38 <84> c0 75 1e 8b
03 65 ff 0d 5d 72 9f 7e 74 0c 83 e0 02 d1 e8 5b 41
RSP: 0018:ffff8880a10ffbe8 EFLAGS: 00000a02
RAX: 1ffff11015d66b00 RBX: ffff8880aeb35fb8 RCX: ffffffff81628ad7
RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff8880aeb35fb8
RBP: ffff8880a10ffc00 R08: dffffc0000000000 R09: ffffed1015d66bf8
R10: ffffed1015d66bf8 R11: 1ffff11015d66bf7 R12: dffffc0000000000
R13: ffff8880a93c9b00 R14: ffffffff8881f258 R15: dffffc0000000000
FS: 0000000000000000(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c434bbb720 CR3: 000000008e6fa000 CR4: 00000000001406e0
Call Trace:
rcu_read_lock include/linux/rcupdate.h:594 [inline]
batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:407 [inline]
batadv_nc_worker+0x115/0x600 net/batman-adv/network-coding.c:718
process_one_work+0x814/0x1130 kernel/workqueue.c:2269
worker_thread+0xc01/0x1640 kernel/workqueue.c:2415
kthread+0x325/0x350 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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[Eric Biggers]

Jens, any idea about this?

[JackieLiu]

Hello Eric Biggers

I have reproduced this problem and are looking for a solution. maybe
just use kthread_unpark to replace kthread_stop in io_uring_release
function.

---
Jackie Liu

Eric Biggers <ebig...@kernel.org> 于2019年7月2日周二 下午2:01写道：

[JackieLiu]

Test program like that:

#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 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);
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++)
{
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 < 5 * 1000)
continue;
kill_and_wait(pid, &status);
break;
}
}
}

#ifndef __NR_io_uring_setup
#define __NR_io_uring_setup 425
#endif

void execute_one(void)
{
*(uint32_t *)0x20000080 = 0;
*(uint32_t *)0x20000084 = 0;
*(uint32_t *)0x20000088 = 3;
*(uint32_t *)0x2000008c = 3;
*(uint32_t *)0x20000090 = 0x175;
*(uint32_t *)0x20000094 = 0;
*(uint32_t *)0x20000098 = 0;
*(uint32_t *)0x2000009c = 0;
*(uint32_t *)0x200000a0 = 0;
*(uint32_t *)0x200000a4 = 0;
*(uint32_t *)0x200000a8 = 0;
*(uint32_t *)0x200000ac = 0;
*(uint32_t *)0x200000b0 = 0;
*(uint32_t *)0x200000b4 = 0;
*(uint32_t *)0x200000b8 = 0;
*(uint32_t *)0x200000bc = 0;
*(uint32_t *)0x200000c0 = 0;
*(uint32_t *)0x200000c4 = 0;
*(uint64_t *)0x200000c8 = 0;
*(uint32_t *)0x200000d0 = 0;
*(uint32_t *)0x200000d4 = 0;
*(uint32_t *)0x200000d8 = 0;
*(uint32_t *)0x200000dc = 0;
*(uint32_t *)0x200000e0 = 0;
*(uint32_t *)0x200000e4 = 0;
*(uint32_t *)0x200000e8 = 0;
*(uint32_t *)0x200000ec = 0;
*(uint64_t *)0x200000f0 = 0;
syscall(__NR_io_uring_setup, 0x983, 0x20000080);
}
int main(void)
{
syscall(__NR_mmap, 0x20000000, 0x1000000, 3, 0x32, -1, 0);
loop();
return 0;
}

The test steps are as follows:

1. gcc test.c -o test
2. ./test &
3. ps aux | grep test
again and agin, we need wait print that.
root@localhost:~# ps aux | grep test
root 23718 0.0 0.0 0 0 ttyS0 D 01:23 0:00 [test]
root 934 0.3 0.0 20760 1260 ttyS0 S 01:09 0:22 ./test
root 23766 0.0 0.0 11460 1060 ttyS0 S+ 03:01 0:00 grep
--color=auto test

4. kill -9 934
5.
root@localhost:~# cat /proc/23718/task/23718/stack
[<0>] io_sq_thread_stop+0x3e/0x53
[<0>] io_finish_async+0x14/0x4c
[<0>] io_ring_ctx_free+0x14/0x12d
[<0>] io_ring_ctx_wait_and_kill+0x6e/0x74
[<0>] io_uring_release+0x39/0x43
[<0>] __fput+0xb1/0x220
[<0>] task_work_run+0x79/0xa0
[<0>] do_exit+0x2c1/0xb10
[<0>] do_group_exit+0x35/0xa0
[<0>] __x64_sys_exit_group+0xf/0x10
[<0>] do_syscall_64+0x43/0x110
[<0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

6. process 23718 can't stop now.

JackieLiu <jackie...@gmail.com> 于2019年7月4日周四 上午11:58写道：