[syzbot] INFO: task can't die in ext4_stop_mmpd

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7c832d2f9b95 Add linux-next specific files for 20211015
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=122ad4c8b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=f6ac42766a768877
dashboard link: https://syzkaller.appspot.com/bug?extid=305a8d683b017bc30c3d
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=123dd8dcb00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17e0c9ccb00000

Bisection is inconclusive: the issue happens on the oldest tested release.

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13cd6f68b00000
final oops: https://syzkaller.appspot.com/x/report.txt?x=102d6f68b00000
console output: https://syzkaller.appspot.com/x/log.txt?x=17cd6f68b00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+305a8d...@syzkaller.appspotmail.com

INFO: task syz-executor128:9281 can't die for more than 143 seconds.
task:syz-executor128 state:D stack:27824 pid: 9281 ppid: 6538 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:4965 [inline]
__schedule+0xa9a/0x4940 kernel/sched/core.c:6246
schedule+0xd2/0x260 kernel/sched/core.c:6319
schedule_timeout+0x1db/0x2a0 kernel/time/timer.c:1857
do_wait_for_common kernel/sched/completion.c:85 [inline]
__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common kernel/sched/completion.c:117 [inline]
wait_for_completion+0x174/0x270 kernel/sched/completion.c:138
kthread_stop+0x17a/0x710 kernel/kthread.c:648
ext4_stop_mmpd+0x47/0xd0 fs/ext4/mmp.c:255
ext4_fill_super+0x892d/0xd750 fs/ext4/super.c:5060
mount_bdev+0x34d/0x410 fs/super.c:1368
legacy_get_tree+0x105/0x220 fs/fs_context.c:610
vfs_get_tree+0x89/0x2f0 fs/super.c:1498
do_new_mount fs/namespace.c:2988 [inline]
path_mount+0x1320/0x1fa0 fs/namespace.c:3318
do_mount fs/namespace.c:3331 [inline]
__do_sys_mount fs/namespace.c:3539 [inline]
__se_sys_mount fs/namespace.c:3516 [inline]
__x64_sys_mount+0x27f/0x300 fs/namespace.c:3516
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7ffb61e58d3a
RSP: 002b:00007ffb61e03078 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffb61e030d0 RCX: 00007ffb61e58d3a
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007ffb61e03090
RBP: 000000000000000b R08: 00007ffb61e030d0 R09: 00007ffb61e036bc
R10: 0000000000000000 R11: 0000000000000202 R12: 00007ffb61e03090
R13: 0000000020000308 R14: 0000000000000004 R15: 0000000000000005
</TASK>
INFO: task syz-executor128:9281 blocked for more than 143 seconds.
Not tainted 5.15.0-rc5-next-20211015-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor128 state:D stack:27824 pid: 9281 ppid: 6538 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:4965 [inline]
__schedule+0xa9a/0x4940 kernel/sched/core.c:6246
schedule+0xd2/0x260 kernel/sched/core.c:6319
schedule_timeout+0x1db/0x2a0 kernel/time/timer.c:1857
do_wait_for_common kernel/sched/completion.c:85 [inline]
__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common kernel/sched/completion.c:117 [inline]
wait_for_completion+0x174/0x270 kernel/sched/completion.c:138
kthread_stop+0x17a/0x710 kernel/kthread.c:648
ext4_stop_mmpd+0x47/0xd0 fs/ext4/mmp.c:255
ext4_fill_super+0x892d/0xd750 fs/ext4/super.c:5060
mount_bdev+0x34d/0x410 fs/super.c:1368
legacy_get_tree+0x105/0x220 fs/fs_context.c:610
vfs_get_tree+0x89/0x2f0 fs/super.c:1498
do_new_mount fs/namespace.c:2988 [inline]
path_mount+0x1320/0x1fa0 fs/namespace.c:3318
do_mount fs/namespace.c:3331 [inline]
__do_sys_mount fs/namespace.c:3539 [inline]
__se_sys_mount fs/namespace.c:3516 [inline]
__x64_sys_mount+0x27f/0x300 fs/namespace.c:3516
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7ffb61e58d3a
RSP: 002b:00007ffb61e03078 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffb61e030d0 RCX: 00007ffb61e58d3a
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007ffb61e03090
RBP: 000000000000000b R08: 00007ffb61e030d0 R09: 00007ffb61e036bc
R10: 0000000000000000 R11: 0000000000000202 R12: 00007ffb61e03090
R13: 0000000020000308 R14: 0000000000000004 R15: 0000000000000005
</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/27:
#0: ffffffff8bb82ea0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6458
1 lock held by systemd-udevd/2978:
1 lock held by in:imklog/6232:
3 locks held by kworker/1:0/6527:
#0: ffff888010c64d38 ((wq_completion)events){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: ffff888010c64d38 ((wq_completion)events){+.+.}-{0:0}, at: arch_atomic_long_set include/linux/atomic/atomic-long.h:41 [inline]
#0: ffff888010c64d38 ((wq_completion)events){+.+.}-{0:0}, at: atomic_long_set include/linux/atomic/atomic-instrumented.h:1198 [inline]
#0: ffff888010c64d38 ((wq_completion)events){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:634 [inline]
#0: ffff888010c64d38 ((wq_completion)events){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:661 [inline]
#0: ffff888010c64d38 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x896/0x1690 kernel/workqueue.c:2268
#1: ffffc90001a8fdb0 ((work_completion)(&pwq->unbound_release_work)){+.+.}-{0:0}, at: process_one_work+0x8ca/0x1690 kernel/workqueue.c:2272
#2: ffffffff8bb8c228 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:290 [inline]
#2: ffffffff8bb8c228 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x4fa/0x620 kernel/rcu/tree_exp.h:839
2 locks held by systemd-udevd/6575:
#0: ffff88801ac02918 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev.part.0+0x9b/0xb60 block/bdev.c:817
#1: ffff888146e0a3f8 (&lo->lo_mutex){+.+.}-{3:3}, at: lo_open+0x75/0x120 drivers/block/loop.c:2040
2 locks held by kworker/1:3/6581:
#0: ffff888010c66538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: ffff888010c66538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: arch_atomic_long_set include/linux/atomic/atomic-long.h:41 [inline]
#0: ffff888010c66538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: atomic_long_set include/linux/atomic/atomic-instrumented.h:1198 [inline]
#0: ffff888010c66538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:634 [inline]
#0: ffff888010c66538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:661 [inline]
#0: ffff888010c66538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x896/0x1690 kernel/workqueue.c:2268
#1: ffffc900028ffdb0 ((work_completion)(&rew.rew_work)){+.+.}-{0:0}, at: process_one_work+0x8ca/0x1690 kernel/workqueue.c:2272
2 locks held by systemd-udevd/6728:
#0: ffff88801ab30918 (&disk->open_mutex
){+.+.}-{3:3}, at: blkdev_get_by_dev.part.0+0x9b/0xb60 block/bdev.c:817
#1: ffff88801ab1e3f8 (&lo->lo_mutex){+.+.}-{3:3}, at: lo_open+0x75/0x120 drivers/block/loop.c:2040
1 lock held by syz-executor128/9281:
#0: ffff88801e23e0e0 (&type->s_umount_key#27/1){+.+.}-{3:3}, at: alloc_super+0x1dd/0xac0 fs/super.c:229
3 locks held by kworker/1:6/16911:
#0: ffff888010c64d38 ((wq_completion)events){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: ffff888010c64d38 ((wq_completion)events){+.+.}-{0:0}, at: arch_atomic_long_set include/linux/atomic/atomic-long.h:41 [inline]
#0: ffff888010c64d38 ((wq_completion)events){+.+.}-{0:0}, at: atomic_long_set include/linux/atomic/atomic-instrumented.h:1198 [inline]
#0: ffff888010c64d38 ((wq_completion)events){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:634 [inline]
#0: ffff888010c64d38 ((wq_completion)events){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:661 [inline]
#0: ffff888010c64d38 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x896/0x1690 kernel/workqueue.c:2268
#1: ffffc9000a257db0 ((work_completion)(&pwq->unbound_release_work)){+.+.}-{0:0}, at: process_one_work+0x8ca/0x1690 kernel/workqueue.c:2272
#2: ffffffff8bb8c228 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:322 [inline]
#2: ffffffff8bb8c228 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x2d5/0x620 kernel/rcu/tree_exp.h:839
1 lock held by syz-executor128/25260:
#0: ffff8880770940e0 (&type->s_umount_key#27/1){+.+.}-{3:3}, at: alloc_super+0x1dd/0xac0 fs/super.c:229
1 lock held by syz-executor128/1607:
#0: ffff888146e0a3f8 (&lo->lo_mutex){+.+.}-{3:3}, at: __loop_clr_fd+0xaf/0x15e0 drivers/block/loop.c:1350
1 lock held by syz-executor128/1608:
#0: ffff88801ab1e3f8 (&lo->lo_mutex){+.+.}-{3:3}, at: __loop_clr_fd+0xaf/0x15e0 drivers/block/loop.c:1350
1 lock held by syz-executor128/1621:
#0: ffff88801ab1b3f8 (&lo->lo_mutex){+.+.}-{3:3}, at: __loop_clr_fd+0xaf/0x15e0 drivers/block/loop.c:1350
1 lock held by syz-executor128/1630:
#0: ffff88801ab3c3f8 (&lo->lo_mutex){+.+.}-{3:3}, at: __loop_clr_fd+0xaf/0x15e0 drivers/block/loop.c:1350

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

NMI backtrace for cpu 0
CPU: 0 PID: 27 Comm: khungtaskd Not tainted 5.15.0-rc5-next-20211015-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
nmi_cpu_backtrace.cold+0x47/0x144 lib/nmi_backtrace.c:105
nmi_trigger_cpumask_backtrace+0x1ae/0x220 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:254 [inline]
watchdog+0xcb7/0xed0 kernel/hung_task.c:339
kthread+0x405/0x4f0 kernel/kthread.c:327
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 2968 Comm: systemd-journal Not tainted 5.15.0-rc5-next-20211015-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:preempt_count arch/x86/include/asm/preempt.h:27 [inline]
RIP: 0010:check_kcov_mode kernel/kcov.c:166 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x0/0x60 kernel/kcov.c:200
Code: 48 89 ef 5d e9 41 f4 45 00 5d be 03 00 00 00 e9 f6 80 60 02 66 0f 1f 44 00 00 48 8b be b0 01 00 00 e8 b4 ff ff ff 31 c0 c3 90 <65> 8b 05 69 0b 8b 7e 89 c1 48 8b 34 24 81 e1 00 01 00 00 65 48 8b
RSP: 0018:ffffc90000dc0c38 EFLAGS: 00000006
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000000003
RDX: 0000000000000000 RSI: ffff88807ad0ba00 RDI: 0000000000000003
RBP: 00000000ffffffff R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff84087dd5 R11: 0000000000000000 R12: 0000000000000001
R13: ffffed10173a4f0d R14: 0000000000000002 R15: 0000000000000001
FS: 00007f37549478c0(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f3752224648 CR3: 000000002248c000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>
__ffs arch/x86/include/asm/bitops.h:235 [inline]
find_next_bit include/linux/find.h:41 [inline]
cpumask_next lib/cpumask.c:22 [inline]
cpumask_next_wrap+0x6c/0x1b0 lib/cpumask.c:82
select_idle_cpu kernel/sched/fair.c:6281 [inline]
select_idle_sibling kernel/sched/fair.c:6452 [inline]
select_task_rq_fair+0xccf/0x3b50 kernel/sched/fair.c:6929
select_task_rq kernel/sched/core.c:3400 [inline]
try_to_wake_up+0x38b/0x15a0 kernel/sched/core.c:4082
hrtimer_wakeup+0x43/0x60 kernel/time/hrtimer.c:1939
__run_hrtimer kernel/time/hrtimer.c:1685 [inline]
__hrtimer_run_queues+0x609/0xe50 kernel/time/hrtimer.c:1749
hrtimer_interrupt+0x31c/0x790 kernel/time/hrtimer.c:1811
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1086 [inline]
__sysvec_apic_timer_interrupt+0x146/0x530 arch/x86/kernel/apic/apic.c:1103
sysvec_apic_timer_interrupt+0x8e/0xc0 arch/x86/kernel/apic/apic.c:1097
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:638
RIP: 0010:access_override_creds fs/open.c:358 [inline]
RIP: 0010:do_faccessat+0x4e2/0x850 fs/open.c:415
Code: 25 40 70 02 00 49 8d be 20 08 00 00 48 89 fa 89 45 30 48 c1 ea 03 48 b8 00 00 00 00 00 fc ff df 80 3c 02 00 0f 85 fd 02 00 00 <4d> 8b b6 20 08 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7e 34 48
RSP: 0018:ffffc90001b0fe88 EFLAGS: 00000246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 1ffff1100f5a1844 RSI: ffffffff81c7a325 RDI: ffff88807ad0c220
RBP: ffff88801a435500 R08: 0000000043736564 R09: ffff888010db4ab3
R10: ffffffff814e5de9 R11: 0000000000000000 R12: 0000000000000001
R13: ffff88801a435514 R14: ffff88807ad0ba00 R15: 0000000000000000
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f3753c029c7
Code: 83 c4 08 48 3d 01 f0 ff ff 73 01 c3 48 8b 0d c8 d4 2b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 b8 15 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d a1 d4 2b 00 f7 d8 64 89 01 48
RSP: 002b:00007fff031591e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000015
RAX: ffffffffffffffda RBX: 00007fff0315c100 RCX: 00007f3753c029c7
RDX: 00007f3754673a00 RSI: 0000000000000000 RDI: 000056048df759a3
RBP: 00007fff03159220 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000069 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fff0315c100 R15: 00007fff03159710
</TASK>
INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.212 msecs
----------------
Code disassembly (best guess):
0: 48 89 ef mov %rbp,%rdi
3: 5d pop %rbp
4: e9 41 f4 45 00 jmpq 0x45f44a
9: 5d pop %rbp
a: be 03 00 00 00 mov $0x3,%esi
f: e9 f6 80 60 02 jmpq 0x260810a
14: 66 0f 1f 44 00 00 nopw 0x0(%rax,%rax,1)
1a: 48 8b be b0 01 00 00 mov 0x1b0(%rsi),%rdi
21: e8 b4 ff ff ff callq 0xffffffda
26: 31 c0 xor %eax,%eax
28: c3 retq
29: 90 nop
* 2a: 65 8b 05 69 0b 8b 7e mov %gs:0x7e8b0b69(%rip),%eax # 0x7e8b0b9a <-- trapping instruction
31: 89 c1 mov %eax,%ecx
33: 48 8b 34 24 mov (%rsp),%rsi
37: 81 e1 00 01 00 00 and $0x100,%ecx
3d: 65 gs
3e: 48 rex.W
3f: 8b .byte 0x8b


---
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https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.