INFO: task hung in nbd

INFO: task hung in nbd_ioctl
Status: fixed on 2019/11/06 12:39
Reported-by: syzbot+24c12fa8d218ed26011a@syzkaller.appspotmail.com
Fix commit: cf1b2326b734 nbd: verify socket is supported during setup
First crash: 754d, last: 682d

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: C syz .config

similar bugs (6):
Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
linux-4.14	INFO: task hung in nbd_ioctl	C		done	18	630d	704d	1/1	fixed on 2019/12/28 10:32
linux-4.14	INFO: task hung in nbd_ioctl (2)	C		done	16	377d	623d	1/1	fixed on 2020/10/21 11:01
upstream	INFO: task hung in nbd_ioctl (2)				37	385d	438d	17/22	fixed on 2020/09/25 01:17
linux-4.19	INFO: task hung in nbd_ioctl	C			53	22d	706d	0/1	upstream: reported C repro on 2019/10/12 13:11
upstream	INFO: task hung in nbd_ioctl (3)	C	done	unreliable	11	6d17h	354d	0/22	upstream: reported C repro on 2020/09/28 07:17
linux-4.14	INFO: task hung in nbd_ioctl (3)	C			7	4d18h	308d	0/1	upstream: reported C repro on 2020/11/13 07:37

Sample crash report:

INFO: task syz-executor039:7883 blocked for more than 143 seconds.
      Not tainted 5.4.0-rc4+ #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor039 D27984  7883   7880 0x00004004
Call Trace:
 context_switch kernel/sched/core.c:3384 [inline]
 __schedule+0x74b/0xb80 kernel/sched/core.c:4069
 schedule+0x131/0x1e0 kernel/sched/core.c:4136
 schedule_timeout+0x46/0x240 kernel/time/timer.c:1871
 do_wait_for_common+0x2e7/0x4d0 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
 flush_workqueue+0x60d/0x14b0 kernel/workqueue.c:2826
 nbd_start_device_ioctl drivers/block/nbd.c:1272 [inline]
 __nbd_ioctl drivers/block/nbd.c:1347 [inline]
 nbd_ioctl+0x9d2/0xac0 drivers/block/nbd.c:1387
 __blkdev_driver_ioctl block/ioctl.c:304 [inline]
 blkdev_ioctl+0x807/0x2980 block/ioctl.c:606
 block_ioctl+0xbd/0x100 fs/block_dev.c:1954
 do_vfs_ioctl+0x744/0x1730 fs/ioctl.c:46
 ksys_ioctl fs/ioctl.c:713 [inline]
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0xe3/0x120 fs/ioctl.c:718
 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4496e9
Code: 00 61 64 64 69 6e 67 20 61 20 72 75 6c 65 73 65 74 2d 73 70 65 63 69 66 69 63 20 22 6d 61 69 6e 22 20 71 75 65 75 65 00 00 70 <72> 6f 63 65 73 73 42 61 74 63 68 3a 20 62 61 74 63 68 20 6f 66 20
RSP: 002b:00007fd715da2ce8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000006dac48 RCX: 00000000004496e9
RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000005
RBP: 00000000006dac40 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dac4c
R13: 00007ffd73e6239f R14: 00007fd715da39c0 R15: 20c49ba5e353f7cf

Showing all locks held in the system:
1 lock held by khungtaskd/1070:
 #0: ffffffff888d3f80 (rcu_read_lock){....}, at: rcu_lock_acquire+0x4/0x30 include/linux/rcupdate.h:207
2 locks held by kworker/u5:0/1527:
 #0: ffff88809fa37d28 ((wq_completion)knbd0-recv){+.+.}, at: spin_unlock_irq include/linux/spinlock.h:388 [inline]
 #0: ffff88809fa37d28 ((wq_completion)knbd0-recv){+.+.}, at: process_one_work+0x75d/0x10e0 kernel/workqueue.c:2242
 #1: ffff8880a637fd78 ((work_completion)(&args->work)){+.+.}, at: process_one_work+0x79f/0x10e0 kernel/workqueue.c:2244
1 lock held by rsyslogd/7770:
 #0: ffff8880a04f7420 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x243/0x2e0 fs/file.c:801
2 locks held by getty/7860:
 #0: ffff88809b3bd090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:272
 #1: ffffc90005f352e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x221/0x1b00 drivers/tty/n_tty.c:2156
2 locks held by getty/7861:
 #0: ffff888090daf090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:272
 #1: ffffc90005f212e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x221/0x1b00 drivers/tty/n_tty.c:2156
2 locks held by getty/7862:
 #0: ffff8880a3a20090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:272
 #1: ffffc90005f392e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x221/0x1b00 drivers/tty/n_tty.c:2156
2 locks held by getty/7863:
 #0: ffff8880a7bcc090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:272
 #1: ffffc90005f152e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x221/0x1b00 drivers/tty/n_tty.c:2156
2 locks held by getty/7864:
 #0: ffff8880a35b0090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:272
 #1: ffffc90005f192e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x221/0x1b00 drivers/tty/n_tty.c:2156
2 locks held by getty/7865:
 #0: ffff8880a2541090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:272
 #1: ffffc90005f2d2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x221/0x1b00 drivers/tty/n_tty.c:2156
2 locks held by getty/7866:
 #0: ffff88809b0f8090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:272
 #1: ffffc90005f012e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x221/0x1b00 drivers/tty/n_tty.c:2156

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

NMI backtrace for cpu 1
CPU: 1 PID: 1070 Comm: khungtaskd Not tainted 5.4.0-rc4+ #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+0x1d8/0x2f8 lib/dump_stack.c:113
 nmi_cpu_backtrace+0xaf/0x1a0 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x174/0x290 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+0x332/0x350 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:60

Crashes (71):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro
ci-upstream-kasan-gce-smack-root	2019/10/22 14:19	upstream	3b7c59a1950c	c59a7cd8	.config	log	report	syz	C
ci-upstream-kasan-gce-root	2019/10/06 18:52	upstream	43b815c6a8e7	f3f7d9c8	.config	log	report	syz	C
ci-upstream-linux-next-kasan-gce-root	2019/09/28 00:50	linux-next	bb2aee77c82d	d8074e0b	.config	log	report	syz	C
ci-upstream-kasan-gce-root	2019/11/05 08:34	upstream	a99d8080aaf3	76630fc9	.config	log	report
ci-upstream-kasan-gce-root	2019/10/30 11:27	upstream	23fdb198ae81	5ea87a66	.config	log	report
ci-upstream-kasan-gce-selinux-root	2019/10/26 04:20	upstream	8caacaad78b6	c2e837da	.config	log	report
ci-upstream-kasan-gce-root	2019/10/25 22:34	upstream	39a38bcba4ab	c2e837da	.config	log	report
ci-upstream-kasan-gce-smack-root	2019/10/25 09:09	upstream	39a38bcba4ab	d01bb02a	.config	log	report
ci-upstream-kasan-gce-selinux-root	2019/10/22 08:11	upstream	7d194c2100ad	c59a7cd8	.config	log	report
ci-upstream-kasan-gce-root	2019/10/21 07:15	upstream	4fe34d61a3a9	8c88c9c1	.config	log	report
ci-upstream-kasan-gce-smack-root	2019/10/19 12:01	upstream	b9959c7a347d	8c88c9c1	.config	log	report
ci-upstream-kasan-gce-root	2019/10/19 10:01	upstream	b9959c7a347d	8c88c9c1	.config	log	report
ci-upstream-kasan-gce-root	2019/10/18 19:06	upstream	0e2adab6cf28	8c88c9c1	.config	log	report
ci-upstream-kasan-gce-smack-root	2019/10/18 06:56	upstream	283ea345934d	8c88c9c1	.config	log	report
ci-upstream-kasan-gce-selinux-root	2019/10/17 07:56	upstream	bc88f85c6c09	8c88c9c1	.config	log	report
ci-upstream-kasan-gce-smack-root	2019/10/16 16:06	upstream	3b1f00aceb7a	d4ea592f	.config	log	report
ci-upstream-kasan-gce-selinux-root	2019/10/16 13:41	upstream	3b1f00aceb7a	d4ea592f	.config	log	report
ci-upstream-kasan-gce-root	2019/10/13 23:44	upstream	da94001239cc	2f661ec4	.config	log	report
ci-upstream-kasan-gce-selinux-root	2019/10/12 04:54	upstream	9e208aa06c21	426631dd	.config	log	report
ci-upstream-kasan-gce-selinux-root	2019/10/11 13:00	upstream	fb20da6af705	1a3bad90	.config	log	report
ci-upstream-kasan-gce-smack-root	2019/10/06 17:46	upstream	43b815c6a8e7	f3f7d9c8	.config	log	report
ci-upstream-kasan-gce-root	2019/10/06 11:13	upstream	43b815c6a8e7	f3f7d9c8	.config	log	report
ci-upstream-kasan-gce-selinux-root	2019/10/06 07:25	upstream	4ea655343ce4	f3f7d9c8	.config	log	report
ci-upstream-kasan-gce-smack-root	2019/10/06 06:53	upstream	4ea655343ce4	f3f7d9c8	.config	log	report
ci-upstream-kasan-gce-root	2019/10/05 04:29	upstream	b145b0eb2031	f3f7d9c8	.config	log	report
ci-upstream-kasan-gce-smack-root	2019/10/05 02:43	upstream	b145b0eb2031	f3f7d9c8	.config	log	report
ci-upstream-kasan-gce-root	2019/10/05 00:45	upstream	b145b0eb2031	f3f7d9c8	.config	log	report
ci-upstream-kasan-gce-selinux-root	2019/10/04 11:09	upstream	cc3a7bfe62b9	fc17ba49	.config	log	report
ci-upstream-kasan-gce-root	2019/10/02 21:31	upstream	54ecb8f7028c	2e29b534	.config	log	report
ci-upstream-kasan-gce-selinux-root	2019/10/01 22:33	upstream	54ecb8f7028c	b7a87a83	.config	log	report
ci-upstream-kasan-gce-selinux-root	2019/10/01 04:46	upstream	54ecb8f7028c	c7a4fb99	.config	log	report
ci-upstream-kasan-gce-smack-root	2019/09/30 21:54	upstream	97f9a3c4eee5	c7a4fb99	.config	log	report
ci-upstream-kasan-gce-selinux-root	2019/09/29 13:06	upstream	02dc96ef6c25	c1ad5441	.config	log	report
ci-upstream-kasan-gce-smack-root	2019/09/27 06:04	upstream	cbafe18c7102	2f1548bc	.config	log	report
ci-upstream-kasan-gce-root	2019/09/24 06:19	upstream	e94f8ccde471	c68252d2	.config	log	report
ci-upstream-kasan-gce-selinux-root	2019/09/22 18:31	upstream	f7c3bf8fa7e5	d96e88f3	.config	log	report
ci-upstream-kasan-gce-root	2019/09/21 22:53	upstream	227c3e9eb5cf	d96e88f3	.config	log	report
ci-upstream-kasan-gce-selinux-root	2019/09/18 19:17	upstream	35f7a9526615	c2dcd700	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/10/18 13:32	linux-next	c4b9850b3676	8c88c9c1	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/10/16 05:05	linux-next	0e9d28bc6c81	d4ea592f	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/10/14 04:58	linux-next	8ada228ac7ed	2f661ec4	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/10/13 08:05	linux-next	8ada228ac7ed	426631dd	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/10/13 04:43	linux-next	8ada228ac7ed	426631dd	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/10/10 13:35	linux-next	4a9e93dbc796	a4efa8c0	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/10/07 04:08	linux-next	311ef88adfa3	f3f7d9c8	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/10/06 11:57	linux-next	311ef88adfa3	f3f7d9c8	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/10/06 11:03	linux-next	311ef88adfa3	f3f7d9c8	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/09/27 20:39	linux-next	bb2aee77c82d	d8074e0b	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/09/21 20:17	linux-next	b5b3bd898ba9	d96e88f3	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/09/14 22:03	linux-next	6d028043b55e	32d59357	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/09/14 18:57	linux-next	6d028043b55e	32d59357	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/09/14 13:46	linux-next	6d028043b55e	32d59357	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/09/12 22:46	linux-next	6d028043b55e	0b7672ee	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/09/12 07:08	linux-next	6d028043b55e	f4e53c10	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/09/11 19:02	linux-next	6d028043b55e	a60cb4cd	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/09/11 01:56	linux-next	6d028043b55e	a60cb4cd	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/09/10 02:10	linux-next	6d028043b55e	a60cb4cd	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/09/08 20:33	linux-next	6d028043b55e	a60cb4cd	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/09/07 22:12	linux-next	6d028043b55e	a60cb4cd	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/09/07 02:23	linux-next	6d028043b55e	a60cb4cd	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/09/06 08:08	linux-next	6d028043b55e	040fda58	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/08/30 12:49	linux-next	ed2393ca0910	fd37b39e	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/08/30 03:54	linux-next	ed2393ca0910	fd37b39e	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/08/30 01:52	linux-next	ed2393ca0910	fd37b39e	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/08/24 20:16	linux-next	9733a7c62c66	78ded196	.config	log	report