INFO: task hung in nbd

INFO: task hung in nbd_ioctl (3)
Status: upstream: reported syz repro on 2020/09/28 07:17
Reported-by: syzbot+fe03c50d25c0188f7487@syzkaller.appspotmail.com
First crash: 26d, last: 24d

Cause bisection: introduced by (bisect log) :
commit e9e006f5fcf2bab59149cb38a48a4817c1b538b4
Author: Mike Christie <mchristi@redhat.com>
Date: Sun Aug 4 19:10:06 2019 +0000

nbd: fix max number of supported devs

Crash: INFO: task hung in nbd_ioctl (log)
Repro: syz .config

similar bugs (5):
Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
linux-4.14	INFO: task hung in nbd_ioctl	C		done	18	302d	376d	1/1	fixed on 2019/12/28 10:32
linux-4.14	INFO: task hung in nbd_ioctl (2)	C		done	16	49d	294d	1/1	fixed on 2020/10/21 11:01
upstream	INFO: task hung in nbd_ioctl (2)				37	56d	109d	17/17	fixed on 2020/09/25 01:17
upstream	INFO: task hung in nbd_ioctl	C	done		71	353d	389d	14/17	fixed on 2019/11/06 12:39
linux-4.19	INFO: task hung in nbd_ioctl	C			38	3d06h	377d	0/1	upstream: reported C repro on 2019/10/12 13:11

Sample crash report:

INFO: task syz-executor.0:10391 blocked for more than 143 seconds.
      Not tainted 5.9.0-rc7-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor.0  state:D stack:28872 pid:10391 ppid:  6914 flags:0x00004004
Call Trace:
 context_switch kernel/sched/core.c:3778 [inline]
 __schedule+0xec9/0x2280 kernel/sched/core.c:4527
 schedule+0xd0/0x2a0 kernel/sched/core.c:4602
 schedule_timeout+0x1d8/0x250 kernel/time/timer.c:1855
 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+0x163/0x260 kernel/sched/completion.c:138
 flush_workqueue+0x3ff/0x13e0 kernel/workqueue.c:2832
 nbd_start_device_ioctl drivers/block/nbd.c:1330 [inline]
 __nbd_ioctl drivers/block/nbd.c:1407 [inline]
 nbd_ioctl+0x7ac/0xbc4 drivers/block/nbd.c:1447
 __blkdev_driver_ioctl block/ioctl.c:224 [inline]
 blkdev_ioctl+0x28c/0x700 block/ioctl.c:620
 block_ioctl+0xf9/0x140 fs/block_dev.c:1871
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl fs/ioctl.c:739 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:739
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45dd99
Code: Bad RIP value.
RSP: 002b:00007f8f34f3ac78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000012e80 RCX: 000000000045dd99
RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000003
RBP: 000000000118c0a8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118c07c
R13: 00007ffcd808961f R14: 00007f8f34f3b9c0 R15: 000000000118c07c

Showing all locks held in the system:
1 lock held by khungtaskd/1171:
 #0: ffffffff8a067f40 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:5852
1 lock held by systemd-journal/3914:
1 lock held by in:imklog/6559:
 #0: ffff888090c858f0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:930
2 locks held by kworker/u5:5/6979:
 #0: ffff8880963e4138 ((wq_completion)knbd0-recv){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
 #0: ffff8880963e4138 ((wq_completion)knbd0-recv){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline]
 #0: ffff8880963e4138 ((wq_completion)knbd0-recv){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline]
 #0: ffff8880963e4138 ((wq_completion)knbd0-recv){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:616 [inline]
 #0: ffff8880963e4138 ((wq_completion)knbd0-recv){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline]
 #0: ffff8880963e4138 ((wq_completion)knbd0-recv){+.+.}-{0:0}, at: process_one_work+0x82b/0x1670 kernel/workqueue.c:2240
 #1: ffffc90001db7da8 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_one_work+0x85f/0x1670 kernel/workqueue.c:2244
2 locks held by kworker/u4:4/7432:

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

NMI backtrace for cpu 1
CPU: 1 PID: 1171 Comm: khungtaskd Not tainted 5.9.0-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:77 [inline]
 dump_stack+0x198/0x1fd lib/dump_stack.c:118
 nmi_cpu_backtrace.cold+0x70/0xb1 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x1b3/0x223 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+0xd7d/0x1000 kernel/hung_task.c:295
 kthread+0x3b5/0x4a0 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: 7432 Comm: kworker/u4:4 Not tainted 5.9.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: bat_events batadv_nc_worker
RIP: 0010:__lock_is_held kernel/locking/lockdep.c:4792 [inline]
RIP: 0010:lock_is_held_type+0x5b/0xf0 kernel/locking/lockdep.c:5068
Code: 89 fc 31 db e8 e6 cf 34 f9 83 85 e4 08 00 00 01 49 89 c7 8b 85 e0 08 00 00 85 c0 7f 0d eb 7d 83 c3 01 3b 9d e0 08 00 00 7d 72 <48> 63 c3 4c 89 e6 48 8d 04 80 4d 8d 74 c5 00 4c 89 f7 e8 4e fc ff
RSP: 0018:ffffc90002f47b68 EFLAGS: 00000093
RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffffffff815c005f
RDX: dffffc0000000000 RSI: ffffffff8a067e80 RDI: ffff888093dbae28
RBP: ffff888093dba540 R08: 0000000000000000 R09: ffffffff8b59694f
R10: fffffbfff16b2d29 R11: 0000000000000000 R12: ffffffff8a067e80
R13: ffff888093dbae28 R14: ffff888093dbae28 R15: 0000000000000286
FS:  0000000000000000(0000) GS:ffff8880ae400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4d329ef000 CR3: 000000009d52a000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 lock_is_held include/linux/lockdep.h:267 [inline]
 rcu_read_lock_sched_held+0x3a/0xb0 kernel/rcu/update.c:136
 trace_lock_release include/trace/events/lock.h:58 [inline]
 lock_release+0x6a1/0x8f0 kernel/locking/lockdep.c:5040
 rcu_lock_release include/linux/rcupdate.h:246 [inline]
 rcu_read_unlock include/linux/rcupdate.h:688 [inline]
 batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:411 [inline]
 batadv_nc_worker+0x7a3/0xe50 net/batman-adv/network-coding.c:718
 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Crashes (2):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Maintainers
ci-upstream-kasan-gce-selinux-root	2020/09/29 09:51	upstream	fb0155a0	1b88c6d5	.config	log	report	syz			axboe@kernel.dk, josef@toxicpanda.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, nbd@other.debian.org
ci-upstream-kasan-gce-root	2020/09/28 04:35	upstream	a1bffa48	5dd8aee8	.config	log	report	syz			axboe@kernel.dk, josef@toxicpanda.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, nbd@other.debian.org