On Mon, 17 May 2021 04:27:20 -0700
syzbot [off-list ref] wrote:

Hello,

syzbot found the following issue on:

HEAD commit:    2f7b98d1 Merge tag 'drm-fixes-2021-04-16' of
git://anongit.. git tree:       upstream
console output:
https://syzkaller.appspot.com/x/log.txt?x=11966df9d00000 kernel
config:  https://syzkaller.appspot.com/x/.config?x=398c4d0fe6f66e68
dashboard link:
https://syzkaller.appspot.com/bug?extid=deb25600c2fd79ffd367 syz
repro:
https://syzkaller.appspot.com/x/repro.syz?x=170d645ad00000 C
reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16a03a2ed00000

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

bisection log:
https://syzkaller.appspot.com/x/bisect.txt?x=156f54b6d00000 final
oops:     https://syzkaller.appspot.com/x/report.txt?x=176f54b6d00000
console output:
https://syzkaller.appspot.com/x/log.txt?x=136f54b6d00000

IMPORTANT: if you fix the issue, please add the following tag to the
commit: Reported-by:
syzbot+deb25600c2fd79ffd367@syzkaller.appspotmail.com

INFO: task syz-executor768:8400 blocked for more than 143 seconds.
      Not tainted 5.12.0-rc7-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this
message. task:syz-executor768 state:D stack:26912 pid: 8400 ppid:
8395 flags:0x00004000 Call Trace:
 context_switch kernel/sched/core.c:4322 [inline]
 __schedule+0x911/0x21b0 kernel/sched/core.c:5073
 schedule+0xcf/0x270 kernel/sched/core.c:5152
 schedule_timeout+0x1db/0x250 kernel/time/timer.c:1868
 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+0x168/0x270 kernel/sched/completion.c:138
 kthread_stop+0x17a/0x720 kernel/kthread.c:621
 ext4_put_super+0x926/0x10c0 fs/ext4/super.c:1248
 generic_shutdown_super+0x144/0x370 fs/super.c:464
 kill_block_super+0x97/0xf0 fs/super.c:1394
 deactivate_locked_super+0x94/0x160 fs/super.c:335
 deactivate_super+0xad/0xd0 fs/super.c:366
 cleanup_mnt+0x3a3/0x530 fs/namespace.c:1136
 task_work_run+0xdd/0x1a0 kernel/task_work.c:140
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:174 [inline]
 exit_to_user_mode_prepare+0x249/0x250 kernel/entry/common.c:208
 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
 syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:301
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x44bf77
RSP: 002b:00007ffdcafa7108 EFLAGS: 00000202 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00000000000b7da1 RCX: 000000000044bf77
RDX: 00007ffdcafa71cb RSI: 0000000000000002 RDI: 00007ffdcafa71c0
RBP: 00007ffdcafa71c0 R08: 00000000ffffffff R09: 00007ffdcafa6fa0
R10: 00000000015f3663 R11: 0000000000000202 R12: 00007ffdcafa8280
R13: 00000000015f35f0 R14: 00007ffdcafa7130 R15: 00007ffdcafa82a0

Showing all locks held in the system:
3 locks held by kworker/0:2/8:
 #0: ffff888010464d38 ((wq_completion)events){+.+.}-{0:0}, at:
arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0:
ffff888010464d38 ((wq_completion)events){+.+.}-{0:0}, at:
atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline]
#0: ffff888010464d38 ((wq_completion)events){+.+.}-{0:0}, at:
atomic_long_set include/asm-generic/atomic-long.h:41 [inline] #0:
ffff888010464d38 ((wq_completion)events){+.+.}-{0:0}, at:
set_work_data kernel/workqueue.c:616 [inline] #0: ffff888010464d38
((wq_completion)events){+.+.}-{0:0}, at:
set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline] #0:
ffff888010464d38 ((wq_completion)events){+.+.}-{0:0}, at:
process_one_work+0x871/0x1600 kernel/workqueue.c:2246 #1:
ffffc90000cd7da8
((work_completion)(&pwq->unbound_release_work)){+.+.}-{0:0}, at:
process_one_work+0x8a5/0x1600 kernel/workqueue.c:2250 #2:
ffffffff8bf7cf28 (rcu_state.exp_mutex){+.+.}-{3:3}, at:
exp_funnel_lock kernel/rcu/tree_exp.h:290 [inline] #2:
ffffffff8bf7cf28 (rcu_state.exp_mutex){+.+.}-{3:3}, at:
synchronize_rcu_expedited+0x4fa/0x620 kernel/rcu/tree_exp.h:836 1
lock held by khungtaskd/1630: #0: ffffffff8bf74360
(rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260
kernel/locking/lockdep.c:6328 3 locks held by kworker/0:3/3722: #0:
ffff888010464d38 ((wq_completion)events){+.+.}-{0:0}, at:
arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0:
ffff888010464d38 ((wq_completion)events){+.+.}-{0:0}, at:
atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline]
#0: ffff888010464d38 ((wq_completion)events){+.+.}-{0:0}, at:
atomic_long_set include/asm-generic/atomic-long.h:41 [inline] #0:
ffff888010464d38 ((wq_completion)events){+.+.}-{0:0}, at:
set_work_data kernel/workqueue.c:616 [inline] #0: ffff888010464d38
((wq_completion)events){+.+.}-{0:0}, at:
set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline] #0:
ffff888010464d38 ((wq_completion)events){+.+.}-{0:0}, at:
process_one_work+0x871/0x1600 kernel/workqueue.c:2246 #1:
ffffc900032dfda8
((work_completion)(&pwq->unbound_release_work)){+.+.}-{0:0}, at:
process_one_work+0x8a5/0x1600 kernel/workqueue.c:2250 #2:
ffffffff8bf7cf28 (rcu_state.exp_mutex){+.+.}-{3:3}, at:
exp_funnel_lock kernel/rcu/tree_exp.h:322 [inline] #2:
ffffffff8bf7cf28 (rcu_state.exp_mutex){+.+.}-{3:3}, at:
synchronize_rcu_expedited+0x27e/0x620 kernel/rcu/tree_exp.h:836 1
lock held by systemd-udevd/4830: #0: ffff8881426373a0
(&bdev->bd_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev
fs/block_dev.c:1457 [inline] #0: ffff8881426373a0
(&bdev->bd_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev+0x261/0x600
fs/block_dev.c:1426 1 lock held by in:imklog/8093: 2 locks held by
syz-executor768/8398: #0: ffff888142635120
(&bdev->bd_mutex){+.+.}-{3:3}, at: __blkdev_put+0xf0/0x800
fs/block_dev.c:1578 #1: ffff8880196783f0 (&lo->lo_mutex){+.+.}-{3:3},
at: __loop_clr_fd+0x8b/0xff0 drivers/block/loop.c:1203 2 locks held
by syz-executor768/8399: #0: ffff888142635ca0
(&bdev->bd_mutex){+.+.}-{3:3}, at: __blkdev_put+0xf0/0x800
fs/block_dev.c:1578 #1: ffff88801967d3f0 (&lo->lo_mutex){+.+.}-{3:3},
at: __loop_clr_fd+0x8b/0xff0 drivers/block/loop.c:1203 1 lock held by
syz-executor768/8400: #0: ffff8880117360e0
(&type->s_umount_key#41){++++}-{3:3}, at: deactivate_super+0xa5/0xd0
fs/super.c:365 2 locks held by syz-executor768/8401: #0:
ffff8881426373a0 (&bdev->bd_mutex){+.+.}-{3:3}, at:
__blkdev_put+0xf0/0x800 fs/block_dev.c:1578 #1: ffff8880197073f0
(&lo->lo_mutex){+.+.}-{3:3}, at: __loop_clr_fd+0x8b/0xff0
drivers/block/loop.c:1203 2 locks held by kworker/0:1/8519: #0:
ffff888010464d38 ((wq_completion)events){+.+.}-{0:0}, at:
arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0:
ffff888010464d38 ((wq_completion)events){+.+.}-{0:0}, at:
atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline]
#0: ffff888010464d38 ((wq_completion)events){+.+.}-{0:0}, at:
atomic_long_set include/asm-generic/atomic-long.h:41 [inline] #0:
ffff888010464d38 ((wq_completion)events){+.+.}-{0:0}, at:
set_work_data kernel/workqueue.c:616 [inline] #0: ffff888010464d38
((wq_completion)events){+.+.}-{0:0}, at:
set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline] #0:
ffff888010464d38 ((wq_completion)events){+.+.}-{0:0}, at:
process_one_work+0x871/0x1600 kernel/workqueue.c:2246 #1:
ffffc90001c2fda8
((work_completion)(&pwq->unbound_release_work)){+.+.}-{0:0}, at:
process_one_work+0x8a5/0x1600 kernel/workqueue.c:2250 2 locks held by
kworker/0:5/8531: #0: ffff888010466538
((wq_completion)rcu_gp){+.+.}-{0:0}, at: arch_atomic64_set
arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff888010466538
((wq_completion)rcu_gp){+.+.}-{0:0}, at: atomic64_set
include/asm-generic/atomic-instrumented.h:856 [inline] #0:
ffff888010466538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at:
atomic_long_set include/asm-generic/atomic-long.h:41 [inline] #0:
ffff888010466538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at:
set_work_data kernel/workqueue.c:616 [inline] #0: ffff888010466538
((wq_completion)rcu_gp){+.+.}-{0:0}, at:
set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline] #0:
ffff888010466538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at:
process_one_work+0x871/0x1600 kernel/workqueue.c:2246 #1:
ffffc900019afda8 ((work_completion)(&rew.rew_work)){+.+.}-{0:0}, at:
process_one_work+0x8a5/0x1600 kernel/workqueue.c:2250

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

NMI backtrace for cpu 1
CPU: 1 PID: 1630 Comm: khungtaskd Not tainted 5.12.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine,
BIOS Google 01/01/2011 Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x141/0x1d7 lib/dump_stack.c:120
 nmi_cpu_backtrace.cold+0x44/0xd7 lib/nmi_backtrace.c:105
 nmi_trigger_cpumask_backtrace+0x1b3/0x230 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:209 [inline]
 watchdog+0xd48/0xfb0 kernel/hung_task.c:294
 kthread+0x3b1/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 8563 Comm: systemd-udevd Not tainted 5.12.0-rc7-syzkaller
#0 Hardware name: Google Google Compute Engine/Google Compute Engine,
BIOS Google 01/01/2011 RIP: 0010:compound_head
include/linux/page-flags.h:187 [inline] RIP: 0010:virt_to_head_page
include/linux/mm.h:880 [inline] RIP: 0010:kmem_cache_free+0x76/0x740
mm/slub.c:3177 Code: c1 e8 0c 4c 89 6c 24 28 48 c7 44 24 30 00 00 00
00 49 89 c4 48 b8 00 00 00 00 00 ea ff ff 49 c1 e4 06 49 01 c4 49 8b
44 24 08 <48> 8d 50 ff a8 01 4c 0f 45 e2 48 8d 54 24 30 e8 96 86 ff
ff 84 c0 RSP: 0018:ffffc90001dafd30 EFLAGS: 00000282 RAX:
ffffea00006fc601 RBX: ffff88801bf1e620 RCX: 0000000000000000 RDX:
ffff88801bb69c40 RSI: ffffc90001dafd58 RDI: ffff8880105bd140 RBP:
ffff8880105bd140 R08: 0000000000000000 R09: 0000000000000030 R10:
ffffffff813371ca R11: 000000000000003f R12: ffffea00006fc780 R13:
ffff88801bf1e600 R14: 0000000000000020 R15: ffff8880166c08d0 FS:
00007f07042b08c0(0000) GS:ffff8880b9c00000(0000)
knlGS:0000000000000000 CS:  0010 DS: 0000 ES: 0000 CR0:
0000000080050033 CR2: 000055913c8fb828 CR3: 000000001390c000 CR4:
0000000000350ef0 Call Trace: putname+0xe1/0x120 fs/namei.c:259
do_sys_openat2+0x153/0x420 fs/open.c:1196 do_sys_open fs/open.c:1203
[inline] __do_sys_open fs/open.c:1211 [inline]
 __se_sys_open fs/open.c:1207 [inline]
 __x64_sys_open+0x119/0x1c0 fs/open.c:1207
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f07033f6840
Code: 73 01 c3 48 8b 0d 68 77 20 00 f7 d8 64 89 01 48 83 c8 ff c3 66
0f 1f 44 00 00 83 3d 89 bb 20 00 00 75 10 b8 02 00 00 00 0f 05 <48>
3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 1e f6 ff ff 48 89 04 24 RSP:
002b:00007ffc009f2a08 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 000055913b130780 RCX: 00007f07033f6840
RDX: 0000559139200fe3 RSI: 00000000000a0800 RDI: 000055913b11bed0
RBP: 00007ffc009f2b80 R08: 0000559139200670 R09: 0000000000000010
R10: 00007f0703170d70 R11: 0000000000000246 R12: 00007ffc009f2ad0
R13: 000055913b12a900 R14: 0000000000000003 R15: 000000000000000e

#syz test https://linux.googlesource.com/linux/kernel/git/torvalds/linux refs/changes/76/10176/6

---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
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

With regards,
Pavel Skripkin