INFO: rcu detected stall in ext4_file_write

INFO: rcu detected stall in ext4_file_write_iter
Status: fixed on 2020/09/25 01:17
Reported-by: syzbot+7d19c5fe6a3f1161abb7@syzkaller.appspotmail.com
Fix commit: 7e24969022cb block: allow for_each_bvec to support zero len bvec
First crash: 982d, last: 412d

Cause bisection: the issue happens on the oldest tested release (bisect log)
Crash: INFO: rcu detected stall in ext4_file_write_iter (log)
Repro: C syz .config

Fix bisection: fixed by (bisect log) :
commit 7e24969022cbd61ddc586f14824fc205661bb124
Author: Ming Lei <ming.lei@redhat.com>
Date: Mon Aug 17 10:00:55 2020 +0000

block: allow for_each_bvec to support zero len bvec

similar bugs (4):
Kernel	Title	Repro	Count	Last	Reported	Patched	Status
android-49	INFO: rcu detected stall in ext4_file_write_iter	syz	2	847d	888d	0/3	public: reported syz repro on 2019/04/23 08:58
upstream	INFO: rcu detected stall in ext4_file_write_iter (2)		1	350d	350d	0/22	auto-closed as invalid on 2021/01/10 12:58
linux-4.14	INFO: rcu detected stall in ext4_file_write_iter	C	7	5d00h	899d	0/1	upstream: reported C repro on 2019/04/12 16:30
linux-4.19	INFO: rcu detected stall in ext4_file_write_iter	C	7	7d01h	891d	0/1	upstream: reported C repro on 2019/04/20 13:09

Sample crash report:

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (1 GPs behind) idle=5ce/1/0x4000000000000000 softirq=71451/71452 fqs=11 
	(t=10501 jiffies g=80885 q=481)
rcu: rcu_preempt kthread starved for 10480 jiffies! g80885 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
rcu_preempt     R  running task    29472    10      2 0x00004000
Call Trace:
 context_switch kernel/sched/core.c:3458 [inline]
 __schedule+0x8ea/0x2210 kernel/sched/core.c:4219
 schedule+0xd0/0x2a0 kernel/sched/core.c:4294
 schedule_timeout+0x148/0x250 kernel/time/timer.c:1908
 rcu_gp_fqs_loop kernel/rcu/tree.c:1874 [inline]
 rcu_gp_kthread+0xae5/0x1b50 kernel/rcu/tree.c:2044
 kthread+0x3b5/0x4a0 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293
NMI backtrace for cpu 1
CPU: 1 PID: 27186 Comm: syz-executor533 Not tainted 5.8.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x18f/0x20d 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_single_cpu_backtrace include/linux/nmi.h:164 [inline]
 rcu_dump_cpu_stacks+0x194/0x1cf kernel/rcu/tree_stall.h:320
 print_cpu_stall kernel/rcu/tree_stall.h:553 [inline]
 check_cpu_stall kernel/rcu/tree_stall.h:627 [inline]
 rcu_pending kernel/rcu/tree.c:3489 [inline]
 rcu_sched_clock_irq.cold+0x5b3/0xccc kernel/rcu/tree.c:2504
 update_process_times+0x25/0x60 kernel/time/timer.c:1737
 tick_sched_handle+0x9b/0x180 kernel/time/tick-sched.c:176
 tick_sched_timer+0x108/0x290 kernel/time/tick-sched.c:1320
 __run_hrtimer kernel/time/hrtimer.c:1520 [inline]
 __hrtimer_run_queues+0x1d5/0xfc0 kernel/time/hrtimer.c:1584
 hrtimer_interrupt+0x32a/0x930 kernel/time/hrtimer.c:1646
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1080 [inline]
 __sysvec_apic_timer_interrupt+0x142/0x5e0 arch/x86/kernel/apic/apic.c:1097
 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:711
 </IRQ>
 __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
 run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
 sysvec_apic_timer_interrupt+0xe0/0x120 arch/x86/kernel/apic/apic.c:1091
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:585
RIP: 0010:write_comp_data+0x2f/0x80 kernel/kcov.c:218
Code: 05 a6 46 8e 7e 65 48 8b 34 25 00 ff 01 00 a9 00 01 ff 00 74 0f f6 c4 01 74 59 8b 86 04 14 00 00 85 c0 74 4f 8b 86 e0 13 00 00 <83> f8 03 75 44 48 8b 86 e8 13 00 00 8b b6 e4 13 00 00 4c 8b 00 48
RSP: 0018:ffffc900055776e8 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff8395f2ab
RDX: 0000000000000000 RSI: ffff8880a6a78300 RDI: 0000000000000005
RBP: 0000000000000000 R08: 0000000000000000 R09: ffff888083de5abf
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880a06e0c00
R13: 0000000000000000 R14: dffffc0000000000 R15: 0000000000000000
 bvec_iter_advance include/linux/bvec.h:110 [inline]
 iov_iter_copy_from_user_atomic+0x62b/0xbe0 lib/iov_iter.c:1000
 generic_perform_write+0x277/0x4f0 mm/filemap.c:3326
 ext4_buffered_write_iter+0x235/0x4a0 fs/ext4/file.c:270
 ext4_file_write_iter+0x1f3/0x13d0 fs/ext4/file.c:655
 call_write_iter include/linux/fs.h:1908 [inline]
 do_iter_readv_writev+0x567/0x780 fs/read_write.c:713
 do_iter_write+0x188/0x5f0 fs/read_write.c:1018
 vfs_iter_write+0x70/0xa0 fs/read_write.c:1059
 iter_file_splice_write+0x721/0xbe0 fs/splice.c:750
 do_splice_from fs/splice.c:846 [inline]
 do_splice+0xbcd/0x1820 fs/splice.c:1144
 __do_sys_splice fs/splice.c:1419 [inline]
 __se_sys_splice fs/splice.c:1401 [inline]
 __x64_sys_splice+0x198/0x250 fs/splice.c:1401
 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x447cf9
Code: e8 5c e6 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 4b 06 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f3cabb9ecd8 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 00000000006e39e8 RCX: 0000000000447cf9
RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00000000006e39e0 R08: 0000000000010005 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006e39ec
R13: 00007ffc875f6e9f R14: 00007f3cabb9f9c0 R15: 20c49ba5e353f7cf

Crashes (93):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro
ci-upstream-kasan-gce-root	2020/07/28 11:24	upstream	92ed30191993	cb93dc6a	.config	log	report	syz	C
ci-upstream-kasan-gce-selinux-root	2020/07/27 20:57	upstream	92ed30191993	cb93dc6a	.config	log	report	syz	C
ci-upstream-kasan-gce	2020/07/25 15:41	upstream	68845a55c31b	1f7cc1ca	.config	log	report	syz	C
ci-upstream-kasan-gce	2020/07/24 04:54	upstream	d15be546031c	70c104a1	.config	log	report	syz	C
ci-upstream-kasan-gce-smack-root	2019/06/22 20:00	upstream	abf02e2964b3	34bf9440	.config	log	report	syz	C
ci-upstream-kasan-gce-root	2019/05/03 16:28	upstream	ea9866793d1e	1bfa09b9	.config	log	report	syz	C
ci-upstream-kasan-gce-root	2019/04/12 03:29	upstream	2d06b235815e	13030ef8	.config	log	report	syz	C
ci-upstream-kasan-gce-selinux-root	2019/02/22 06:00	upstream	8a61716ff2ab	7ff74a98	.config	log	report	syz	C
ci-upstream-linux-next-kasan-gce-root	2020/07/30 16:29	linux-next	04b457178630	233283a1	.config	log	report	syz	C
ci-upstream-linux-next-kasan-gce-root	2019/06/30 05:07	linux-next	48568d8c7f47	7509bf36	.config	log	report	syz	C
ci-upstream-kasan-gce-root	2020/07/28 01:23	upstream	92ed30191993	cb93dc6a	.config	log	report	syz
ci-upstream-kasan-gce-selinux-root	2020/07/27 09:43	upstream	92ed30191993	51265195	.config	log	report	syz
ci-upstream-kasan-gce-smack-root	2020/07/25 11:27	upstream	68845a55c31b	1f7cc1ca	.config	log	report	syz
ci-upstream-linux-next-kasan-gce-root	2020/07/27 05:47	linux-next	26027945c94a	51265195	.config	log	report	syz
ci-upstream-kasan-gce-selinux-root	2020/08/11 10:29	upstream	00e4db51259a	bacaf5fa	.config	log	report
ci-upstream-kasan-gce-smack-root	2020/07/29 09:26	upstream	6ba1b005ffc3	19a8de55	.config	log	report
ci-upstream-kasan-gce-selinux-root	2020/05/23 21:45	upstream	423b8baf18a8	9682898d	.config	log	report
ci-upstream-kasan-gce-root	2020/04/21 02:39	upstream	ae83d0b416db	98a9f9e6	.config	log	report
ci-upstream-kasan-gce-root	2020/04/18 08:08	upstream	95988fbc7c31	435c6d53	.config	log	report
ci-upstream-kasan-gce-root	2020/04/02 21:11	upstream	7be97138e727	a34e2c33	.config	log	report
ci-upstream-kasan-gce-root	2020/03/26 03:05	upstream	1b649e0bcae7	e8e6c7d2	.config	log	report
ci-upstream-kasan-gce-selinux-root	2020/03/19 18:23	upstream	cd607737f3b8	2c31c529	.config	log	report
ci-upstream-kasan-gce-root	2020/03/11 09:50	upstream	e94148454103	35f53e45	.config	log	report
ci-upstream-kasan-gce-selinux-root	2020/03/04 15:44	upstream	63623fd44972	c88c7b75	.config	log	report
ci-upstream-kasan-gce-selinux-root	2020/02/28 07:43	upstream	f8788d86ab28	59b57593	.config	log	report
ci-upstream-kasan-gce-root	2020/02/17 15:26	upstream	11a48a5a18c6	2b411596	.config	log	report
ci-upstream-kasan-gce-selinux-root	2020/02/17 12:56	upstream	11a48a5a18c6	2b411596	.config	log	report
ci-upstream-kasan-gce-selinux-root	2020/02/15 22:49	upstream	829e69446995	5d7b90f1	.config	log	report
ci-upstream-kasan-gce-smack-root	2020/02/12 14:36	upstream	359c92c02bfa	84f4fc8a	.config	log	report
ci-upstream-kasan-gce-selinux-root	2020/02/12 03:58	upstream	359c92c02bfa	a75b198c	.config	log	report
ci-upstream-kasan-gce-selinux-root	2020/02/11 15:39	upstream	0a679e13ea30	4d1ab643	.config	log	report
ci-upstream-kasan-gce-root	2020/02/03 23:16	upstream	754beeec1d90	93e5e335	.config	log	report
ci-upstream-kasan-gce-root	2020/01/12 22:47	upstream	6327edceb62b	31290a45	.config	log	report
ci-upstream-kasan-gce-smack-root	2020/01/08 02:23	upstream	ae6088216ce4	6738e0b3	.config	log	report
ci-upstream-kasan-gce-smack-root	2020/01/08 01:13	upstream	ae6088216ce4	6738e0b3	.config	log	report
ci-upstream-kasan-gce-root	2019/12/25 18:45	upstream	46cf053efec6	be5c2c81	.config	log	report
ci-upstream-kasan-gce-selinux-root	2019/12/21 11:32	upstream	6398b9fc818e	bc586918	.config	log	report
ci-upstream-kasan-gce-smack-root	2019/12/03 09:47	upstream	596cf45cbf6e	ab342da3	.config	log	report
ci-upstream-kasan-gce-smack-root	2019/12/02 23:38	upstream	596cf45cbf6e	ab342da3	.config	log	report
ci-upstream-kasan-gce-root	2019/07/20 15:14	upstream	abdfd52a295f	1656845f	.config	log	report
ci-upstream-kasan-gce-smack-root	2019/06/20 07:02	upstream	abf02e2964b3	34bf9440	.config	log	report
ci-upstream-kasan-gce-selinux-root	2019/06/14 09:21	upstream	c11fb13a117e	998ccc76	.config	log	report
ci-upstream-kasan-gce-smack-root	2019/06/14 09:19	upstream	c11fb13a117e	998ccc76	.config	log	report
ci-upstream-kasan-gce-root	2019/06/14 09:19	upstream	c11fb13a117e	998ccc76	.config	log	report
ci-upstream-kasan-gce-root	2019/06/13 12:05	upstream	b076173a309e	3f4e812b	.config	log	report
ci-upstream-kasan-gce-smack-root	2019/01/19 05:29	upstream	2339e91d0e66	2103a236	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2020/06/13 19:36	linux-next	e7b08814b16b	dbce178a	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2020/06/13 06:12	linux-next	e7b08814b16b	f4724dd3	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2020/04/14 14:59	linux-next	f19bb13a0eaf	3f3c5574	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2020/03/09 22:00	linux-next	770fbb32d34e	35f53e45	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2020/02/18 07:04	linux-next	c25a951c50dc	1ce142dc	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2020/02/16 03:06	linux-next	9f01828e9e16	5d7b90f1	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2020/02/06 18:46	linux-next	a0c61bf1c773	c91cbc9d	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/07/20 01:36	linux-next	6d21a41b7b1f	1656845f	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/07/02 08:57	linux-next	48a8a5f9a326	cccc4302	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/06/23 05:58	linux-next	dc636f5d78de	34bf9440	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/06/17 14:26	linux-next	a125097c8410	442206d7	.config	log	report