WARNING in kcm_write

WARNING in kcm_write_msgs
Status: upstream: reported C repro on 2020/03/19 07:10
Reported-by: syzbot+52624bdfbf2746d37d70@syzkaller.appspotmail.com
First crash: 356d, last: 4d08h

Cause bisection: the issue happens on the oldest tested release (bisect log)
Crash: WARNING in sysfs_warn_dup (log)
Repro: C syz .config

similar bugs (2):
Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
linux-4.14	WARNING in kcm_write_msgs	C		inconclusive	1	268d	329d	0/1	upstream: reported C repro on 2020/04/12 04:13
linux-4.19	WARNING in kcm_write_msgs	C			1	10d	341d	0/1	upstream: reported C repro on 2020/03/30 19:34

Sample crash report:

------------[ cut here ]------------
WARNING: CPU: 0 PID: 7193 at net/kcm/kcmsock.c:628 kcm_write_msgs+0x1079/0x1320 net/kcm/kcmsock.c:628
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 7193 Comm: syz-executor138 Not tainted 5.7.0-rc2-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+0x1e9/0x30e lib/dump_stack.c:118
 panic+0x264/0x7a0 kernel/panic.c:221
 __warn+0x209/0x210 kernel/panic.c:582
 report_bug+0x1ac/0x2d0 lib/bug.c:195
 fixup_bug arch/x86/kernel/traps.c:175 [inline]
 do_error_trap+0xca/0x1c0 arch/x86/kernel/traps.c:267
 do_invalid_op+0x32/0x40 arch/x86/kernel/traps.c:286
 invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
RIP: 0010:kcm_write_msgs+0x1079/0x1320 net/kcm/kcmsock.c:628
Code: 6c 24 14 89 ee e8 77 d3 05 fa 85 ed 44 0f 45 ed 44 89 e8 48 81 c4 b0 00 00 00 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 b7 cf 05 fa <0f> 0b 41 bd ea ff ff ff e9 4f ff ff ff e8 a5 cf 05 fa 0f 0b e9 0f
RSP: 0018:ffffc900016f7a60 EFLAGS: 00010293
RAX: ffffffff876d91d9 RBX: ffff8880a29eacc0 RCX: ffff8880887d8600
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffff876d89ec R09: fffffbfff16292b6
R10: fffffbfff16292b6 R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000008000 R14: ffff8880a2da4080 R15: 0000000000110000
 kcm_sendmsg+0x1b5e/0x2170 net/kcm/kcmsock.c:1034
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg net/socket.c:672 [inline]
 sock_write_iter+0x2b4/0x3d0 net/socket.c:1004
 call_write_iter include/linux/fs.h:1907 [inline]
 new_sync_write fs/read_write.c:484 [inline]
 __vfs_write+0x54c/0x710 fs/read_write.c:497
 vfs_write+0x274/0x580 fs/read_write.c:559
 ksys_write+0x11b/0x220 fs/read_write.c:612
 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x447039
Code: e8 dc 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 2b 06 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f31c264ad98 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00000000006dcc48 RCX: 0000000000447039
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00000000006dcc40 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dcc4c
R13: 00000000200003c0 R14: 00000000004af628 R15: 000000000000d4f5
Kernel Offset: disabled
Rebooting in 86400 seconds..

Fix bisection attempts:
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro
ci-upstream-kasan-gce-smack-root	2021/03/02 19:41	upstream	7a7fd0de	347a5dc3	.config	log	report	syz	C
ci-upstream-kasan-gce-smack-root	2021/01/10 10:56	upstream	2ff90100	347a5dc3	.config	log	report	syz	C
ci-upstream-kasan-gce-smack-root	2020/11/12 13:08	upstream	3d5e28bf	347a5dc3	.config	log	report	syz	C

Crashes (62):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Title
ci-upstream-kasan-gce-smack-root	2020/04/20 19:40	upstream	ae83d0b4	347a5dc3	.config	log	report	syz	C
ci-upstream-kasan-gce-root	2020/04/19 02:11	upstream	90280eaa	365fba24	.config	log	report	syz	C
ci-upstream-net-this-kasan-gce	2020/03/26 00:43	net	919a23e9	41f049cc	.config	log	report	syz	C
ci-upstream-net-kasan-gce	2020/03/25 23:53	net-next	29f3490b	41f049cc	.config	log	report	syz	C
ci-upstream-net-kasan-gce	2021/01/21 23:13	net-next	9e8789c8	d4f4eca5	.config	log	report			info	WARNING in kcm_write_msgs
ci-upstream-kasan-gce-selinux-root	2020/07/28 17:32	upstream	92ed3019	cb93dc6a	.config	log	report
ci-upstream-kasan-gce	2020/05/05 17:52	upstream	47cf1b42	4b76dd25	.config	log	report
ci-upstream-kasan-gce-selinux-root	2020/04/02 21:57	upstream	7be97138	a34e2c33	.config	log	report
ci-upstream-net-this-kasan-gce	2021/01/16 18:12	net	bcd0cf19	65a7a854	.config	log	report			info
ci-upstream-net-this-kasan-gce	2020/12/11 10:33	net	d9838b1d	f900b48c	.config	log	report			info
ci-upstream-net-this-kasan-gce	2020/12/01 19:28	net	237f977a	07bfe8a5	.config	log	report			info
ci-upstream-net-this-kasan-gce	2020/11/29 03:49	net	4d521943	a0092f9d	.config	log	report			info
ci-upstream-net-this-kasan-gce	2020/11/19 06:03	net	a3dcb3e7	0767f13f	.config	log	report			info
ci-upstream-net-this-kasan-gce	2020/10/13 12:49	net	64a632da	bd69ee0d	.config	log	report			info
ci-upstream-net-this-kasan-gce	2020/09/02 06:47	net	a609d025	abf9ba4f	.config	log	report
ci-upstream-net-this-kasan-gce	2020/08/21 03:21	net	cf96d977	1d75fe45	.config	log	report
ci-upstream-net-this-kasan-gce	2020/07/07 11:02	net	1ca0fafd	51095195	.config	log	report
ci-upstream-net-this-kasan-gce	2020/06/24 07:55	net	b835a71e	54566aff	.config	log	report
ci-upstream-net-this-kasan-gce	2020/06/07 23:34	net	4e2905ad	2c2b926c	.config	log	report
ci-upstream-net-this-kasan-gce	2020/06/07 21:45	net	4e2905ad	2c2b926c	.config	log	report
ci-upstream-net-this-kasan-gce	2020/05/31 07:03	net	05aa69e5	6f3e1c7c	.config	log	report
ci-upstream-net-this-kasan-gce	2020/05/23 21:58	net	d04322a0	9682898d	.config	log	report
ci-upstream-net-this-kasan-gce	2020/05/04 04:32	net	57c7f2bd	58ae5e18	.config	log	report
ci-upstream-net-this-kasan-gce	2020/05/03 02:24	net	dc30b405	5457883a	.config	log	report
ci-upstream-net-this-kasan-gce	2020/05/01 23:46	net	69422a7e	bc734e7a	.config	log	report
ci-upstream-net-this-kasan-gce	2020/04/30 05:13	net	98123074	2dd552a5	.config	log	report
ci-upstream-net-this-kasan-gce	2020/04/26 11:01	net	167ff131	99b258dd	.config	log	report
ci-upstream-net-this-kasan-gce	2020/04/20 03:45	net	9bacd256	9f7c6d12	.config	log	report
ci-upstream-net-this-kasan-gce	2020/04/18 23:21	net	441870ee	365fba24	.config	log	report
ci-upstream-net-this-kasan-gce	2020/03/15 04:32	net	94b18a87	749688d2	.config	log	report
ci-upstream-net-kasan-gce	2020/12/01 22:51	net-next	cb7fb043	07bfe8a5	.config	log	report			info
ci-upstream-net-kasan-gce	2020/09/23 22:08	net-next	748d1c8a	287cd75a	.config	log	report			info
ci-upstream-net-kasan-gce	2020/09/15 15:26	net-next	ed6d9b02	6989d6f6	.config	log	report			info
ci-upstream-net-kasan-gce	2020/09/03 22:35	net-next	22b330b6	abf9ba4f	.config	log	report
ci-upstream-net-kasan-gce	2020/09/02 04:29	net-next	dc1a9bf2	abf9ba4f	.config	log	report
ci-upstream-net-kasan-gce	2020/08/25 06:37	net-next	85eb5bc3	344da168	.config	log	report
ci-upstream-net-kasan-gce	2020/08/11 11:00	net-next	bfdd5aaa	bacaf5fa	.config	log	report
ci-upstream-net-kasan-gce	2020/08/04 17:11	net-next	da795540	80a06902	.config	log	report
ci-upstream-net-kasan-gce	2020/08/01 10:12	net-next	8f3f330d	d895b3be	.config	log	report
ci-upstream-net-kasan-gce	2020/07/31 16:04	net-next	bd69058f	8df85ed9	.config	log	report
ci-upstream-net-kasan-gce	2020/07/23 00:45	net-next	a6c0d093	340ea530	.config	log	report
ci-upstream-net-kasan-gce	2020/07/21 18:46	net-next	71d4364a	21f1765e	.config	log	report
ci-upstream-net-kasan-gce	2020/07/14 07:26	net-next	2be53e0e	ce4c95b3	.config	log	report
ci-upstream-net-kasan-gce	2020/07/02 01:07	net-next	2b04a661	39acb39d	.config	log	report
ci-upstream-net-kasan-gce	2020/06/19 19:53	net-next	cb8e59cc	81abc331	.config	log	report
ci-upstream-net-kasan-gce	2020/06/07 12:24	net-next	cb8e59cc	2c2b926c	.config	log	report
ci-upstream-net-kasan-gce	2020/05/29 20:27	net-next	394f9ebf	3905eaae	.config	log	report
ci-upstream-net-kasan-gce	2020/05/25 22:51	net-next	06ec313e	30927cd7	.config	log	report
ci-upstream-net-kasan-gce	2020/05/17 16:58	net-next	d53b1162	37bccd4e	.config	log	report
ci-upstream-net-kasan-gce	2020/05/14 16:51	net-next	6545be82	2d572622	.config	log	report
ci-upstream-net-kasan-gce	2020/05/12 11:28	net-next	3242956b	160c7698	.config	log	report
ci-upstream-net-kasan-gce	2020/05/07 13:37	net-next	3793faad	98cbd87b	.config	log	report
ci-upstream-net-kasan-gce	2020/05/03 04:23	net-next	115506fe	5457883a	.config	log	report
ci-upstream-net-kasan-gce	2020/04/26 13:08	net-next	6033cebd	99b258dd	.config	log	report
ci-upstream-net-kasan-gce	2020/04/22 20:55	net-next	b86a0373	2e44d63e	.config	log	report
ci-upstream-net-kasan-gce	2020/04/20 10:41	net-next	0fde6e3b	9f7c6d12	.config	log	report
ci-upstream-net-kasan-gce	2020/04/19 09:19	net-next	513a24ff	365fba24	.config	log	report
ci-upstream-net-kasan-gce	2020/04/18 06:52	net-next	2fcd8014	435c6d53	.config	log	report
ci-upstream-net-kasan-gce	2020/04/15 07:11	net-next	63bef48f	3f3c5574	.config	log	report
ci-upstream-net-kasan-gce	2020/03/30 08:58	net-next	41b14502	05736b29	.config	log	report
ci-upstream-net-kasan-gce	2020/03/25 22:48	net-next	29f3490b	41f049cc	.config	log	report