KMSAN: uninit-value in __dev_mc

KMSAN: uninit-value in __dev_mc_del
Status: upstream: reported C repro on 2018/09/17 21:33
Reported-by: syzbot+0ffee94c5c059dbbc2a9@syzkaller.appspotmail.com
First crash: 941d, last: 718d

Patch testing requests:
Created	Duration	User	Patch	Repo	Result
2020/09/14 07:22	9m	anant.thazhemadam@gmail.com	patch	https://github.com/google/kmsan.git master	report log

Sample crash report:

==================================================================
BUG: KMSAN: uninit-value in memcmp+0x11d/0x180 lib/string.c:863
CPU: 1 PID: 6391 Comm: syz-executor546 Not tainted 4.19.0-rc4+ #61
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+0x2f6/0x430 lib/dump_stack.c:113
 kmsan_report+0x183/0x2b0 mm/kmsan/kmsan.c:917
 __msan_warning+0x70/0xc0 mm/kmsan/kmsan_instr.c:500
 memcmp+0x11d/0x180 lib/string.c:863
 __hw_addr_del_ex net/core/dev_addr_lists.c:123 [inline]
 __dev_mc_del+0x169/0x6c0 net/core/dev_addr_lists.c:710
 dev_mc_del+0x6d/0x80 net/core/dev_addr_lists.c:728
 igmp6_group_dropped+0x2c5/0x12e0 net/ipv6/mcast.c:712
 __ipv6_dev_mc_dec+0x6f1/0xbb0 net/ipv6/mcast.c:960
 addrconf_leave_solict net/ipv6/addrconf.c:2110 [inline]
 __ipv6_ifa_notify+0x9c4/0x17c0 net/ipv6/addrconf.c:5696
 addrconf_ifdown+0x1813/0x2670 net/ipv6/addrconf.c:3762
 addrconf_notify+0x2c2/0x5d50 net/ipv6/addrconf.c:3573
 notifier_call_chain kernel/notifier.c:93 [inline]
 __raw_notifier_call_chain kernel/notifier.c:394 [inline]
 raw_notifier_call_chain+0x13e/0x240 kernel/notifier.c:401
 call_netdevice_notifiers_info net/core/dev.c:1733 [inline]
 call_netdevice_notifiers net/core/dev.c:1751 [inline]
 dev_close_many+0x627/0x9e0 net/core/dev.c:1503
 rollback_registered_many+0x9eb/0x2040 net/core/dev.c:7929
 rollback_registered net/core/dev.c:7994 [inline]
 unregister_netdevice_queue+0x547/0xa40 net/core/dev.c:9038
 unregister_netdevice include/linux/netdevice.h:2589 [inline]
 __tun_detach+0x220c/0x2c70 drivers/net/tun.c:729
 tun_detach drivers/net/tun.c:746 [inline]
 tun_chr_close+0xda/0x1c0 drivers/net/tun.c:3272
 __fput+0x4ee/0xe50 fs/file_table.c:278
 ____fput+0x37/0x40 fs/file_table.c:309
 task_work_run+0x457/0x4d0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:193 [inline]
 exit_to_usermode_loop arch/x86/entry/common.c:166 [inline]
 prepare_exit_to_usermode+0x33e/0x410 arch/x86/entry/common.c:197
 syscall_return_slowpath+0xf3/0x790 arch/x86/entry/common.c:268
 do_syscall_64+0xde/0x100 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x63/0xe7
RIP: 0033:0x401450
Code: 01 f0 ff ff 0f 83 b0 0a 00 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 83 3d dd 23 2d 00 00 75 14 b8 03 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 84 0a 00 00 c3 48 83 ec 08 e8 3a 01 00 00
RSP: 002b:00007ffd5d9bb3b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000005 RCX: 0000000000401450
RDX: 00000000200000c0 RSI: 0000000000008914 RDI: 0000000000000005
RBP: 0000000000019c63 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00000000004023f0 R14: 0000000000000000 R15: 0000000000000000

Local variable description: ----buf@igmp6_group_dropped
Variable was created at:
 igmp6_group_dropped+0x49/0x12e0 net/ipv6/mcast.c:700
 __ipv6_dev_mc_dec+0x6f1/0xbb0 net/ipv6/mcast.c:960
==================================================================

Crashes (123):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro
ci-upstream-kmsan-gce	2018/10/01 11:06	https://github.com/google/kmsan.git master	2b752aff	48a50c6b	.config	log	report	syz	C
ci-upstream-kmsan-gce	2018/10/01 10:29	https://github.com/google/kmsan.git master	2b752aff	48a50c6b	.config	log	report	syz	C
ci-upstream-kmsan-gce	2018/09/28 12:00	https://github.com/google/kmsan.git master	23005322	8bb1f0fc	.config	log	report	syz	C
ci-upstream-kmsan-gce	2018/09/16 11:21	https://github.com/google/kmsan.git master	5815ca49	a343a400	.config	log	report	syz	C
ci-upstream-kmsan-gce	2019/04/28 03:14	https://github.com/google/kmsan.git master	199a02db	b617407b	.config	log	report
ci-upstream-kmsan-gce	2019/04/27 23:51	https://github.com/google/kmsan.git master	199a02db	b617407b	.config	log	report
ci-upstream-kmsan-gce	2019/04/27 21:34	https://github.com/google/kmsan.git master	199a02db	b617407b	.config	log	report
ci-upstream-kmsan-gce	2019/04/25 08:21	https://github.com/google/kmsan.git master	199a02db	8e3c52b1	.config	log	report
ci-upstream-kmsan-gce	2019/04/21 09:51	https://github.com/google/kmsan.git master	199a02db	b0e8efcb	.config	log	report
ci-upstream-kmsan-gce	2019/04/21 03:24	https://github.com/google/kmsan.git master	199a02db	b0e8efcb	.config	log	report
ci-upstream-kmsan-gce	2019/04/18 00:57	https://github.com/google/kmsan.git master	199a02db	b0e8efcb	.config	log	report
ci-upstream-kmsan-gce	2019/04/12 01:31	https://github.com/google/kmsan.git master	199a02db	13030ef8	.config	log	report
ci-upstream-kmsan-gce	2019/04/11 14:45	https://github.com/google/kmsan.git master	199a02db	e955ac50	.config	log	report
ci-upstream-kmsan-gce	2019/04/10 03:07	https://github.com/google/kmsan.git master	c1f8455d	65b612b7	.config	log	report
ci-upstream-kmsan-gce	2019/04/09 07:27	https://github.com/google/kmsan.git master	c1f8455d	995065ff	.config	log	report
ci-upstream-kmsan-gce	2019/04/07 15:54	https://github.com/google/kmsan.git master	46200eb9	c34fde03	.config	log	report
ci-upstream-kmsan-gce	2019/04/06 22:42	https://github.com/google/kmsan.git master	46200eb9	c34fde03	.config	log	report
ci-upstream-kmsan-gce	2019/04/06 17:57	https://github.com/google/kmsan.git master	46200eb9	c34fde03	.config	log	report
ci-upstream-kmsan-gce	2019/04/05 14:55	https://github.com/google/kmsan.git master	46200eb9	40f2363e	.config	log	report
ci-upstream-kmsan-gce	2019/04/05 00:44	https://github.com/google/kmsan.git master	46200eb9	e5d1b3ac	.config	log	report
ci-upstream-kmsan-gce	2019/04/04 20:29	https://github.com/google/kmsan.git master	46200eb9	6a475fff	.config	log	report
ci-upstream-kmsan-gce	2019/04/04 19:11	https://github.com/google/kmsan.git master	46200eb9	6a475fff	.config	log	report
ci-upstream-kmsan-gce	2019/04/02 17:35	https://github.com/google/kmsan.git master	088c01ea	dfd3394d	.config	log	report
ci-upstream-kmsan-gce	2019/04/01 21:34	https://github.com/google/kmsan.git master	088c01ea	a9ca43d4	.config	log	report
ci-upstream-kmsan-gce	2019/03/31 03:26	https://github.com/google/kmsan.git master	088c01ea	0c624d4d	.config	log	report
ci-upstream-kmsan-gce	2019/03/30 05:08	https://github.com/google/kmsan.git master	088c01ea	c35ee0ea	.config	log	report
ci-upstream-kmsan-gce	2019/03/30 03:11	https://github.com/google/kmsan.git master	088c01ea	c35ee0ea	.config	log	report
ci-upstream-kmsan-gce	2019/03/30 01:14	https://github.com/google/kmsan.git master	088c01ea	c35ee0ea	.config	log	report
ci-upstream-kmsan-gce	2019/03/28 00:14	https://github.com/google/kmsan.git master	3c26d882	4e668495	.config	log	report
ci-upstream-kmsan-gce	2019/03/26 07:59	https://github.com/google/kmsan.git master	3c26d882	55684ce1	.config	log	report
ci-upstream-kmsan-gce	2019/03/25 11:27	https://github.com/google/kmsan.git master	c10a026b	2c86e0a5	.config	log	report
ci-upstream-kmsan-gce	2019/03/24 10:39	https://github.com/google/kmsan.git master	c10a026b	acbc5b7d	.config	log	report
ci-upstream-kmsan-gce	2019/03/21 17:43	https://github.com/google/kmsan.git master	c10a026b	dce6e62f	.config	log	report
ci-upstream-kmsan-gce	2019/03/17 19:04	https://github.com/google/kmsan.git master	43cfd3b1	ba18afea	.config	log	report
ci-upstream-kmsan-gce	2019/03/15 07:35	https://github.com/google/kmsan.git master	9536b452	d72db19b	.config	log	report
ci-upstream-kmsan-gce	2019/03/14 23:22	https://github.com/google/kmsan.git master	9536b452	d72db19b	.config	log	report
ci-upstream-kmsan-gce	2019/03/14 21:39	https://github.com/google/kmsan.git master	9536b452	d72db19b	.config	log	report
ci-upstream-kmsan-gce	2019/03/14 06:11	https://github.com/google/kmsan.git master	c530a275	2881fc25	.config	log	report
ci-upstream-kmsan-gce	2019/03/07 22:45	https://github.com/google/kmsan.git master	a695dc5e	4b69c3cb	.config	log	report
ci-upstream-kmsan-gce	2019/03/06 13:35	https://github.com/google/kmsan.git master	a695dc5e	05cf83bf	.config	log	report
ci-upstream-kmsan-gce	2019/03/04 22:37	https://github.com/google/kmsan.git master	fa1981be	7c693b52	.config	log	report
ci-upstream-kmsan-gce	2019/03/01 07:20	https://github.com/google/kmsan.git master	fa1981be	8a4b3a6b	.config	log	report
ci-upstream-kmsan-gce	2019/02/22 18:47	https://github.com/google/kmsan.git master	fa1981be	6a5fcca4	.config	log	report
ci-upstream-kmsan-gce	2019/02/19 18:54	https://github.com/google/kmsan.git master	fa1981be	4df543c9	.config	log	report
ci-upstream-kmsan-gce	2019/02/19 01:02	https://github.com/google/kmsan.git master	fa1981be	59f36113	.config	log	report
ci-upstream-kmsan-gce	2019/02/18 14:35	https://github.com/google/kmsan.git master	fa1981be	59f36113	.config	log	report
ci-upstream-kmsan-gce	2019/02/13 18:05	https://github.com/google/kmsan.git master	fa1981be	0a49c954	.config	log	report
ci-upstream-kmsan-gce	2018/09/16 07:32	https://github.com/google/kmsan.git master	5815ca49	a343a400	.config	log	report