KMSAN: uninit-value in __dev_mc

[upstream] 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: 33d, last: 6d04h

Sample crash report:

IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
8021q: adding VLAN 0 to HW filter on device team0
IPv6: ADDRCONF(NETDEV_CHANGE): vcan0: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): vcan0: link becomes ready
==================================================================
BUG: KMSAN: uninit-value in memcmp+0x11d/0x180 lib/string.c:863
CPU: 1 PID: 4510 Comm: syz-executor267 Not tainted 4.19.0-rc3+ #48
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+0x14b/0x190 lib/dump_stack.c:113
 kmsan_report+0x183/0x2b0 mm/kmsan/kmsan.c:956
 __msan_warning+0x70/0xc0 mm/kmsan/kmsan_instr.c:645
 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
 ip_mc_filter_del net/ipv4/igmp.c:1129 [inline]
 igmp_group_dropped+0x21a/0x1280 net/ipv4/igmp.c:1262
 ip_mc_down+0x1d9/0x3e0 net/ipv4/igmp.c:1712
 inetdev_event+0x238/0x1d70 net/ipv4/devinet.c:1522
 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+0x4cf/0xc20 fs/file_table.c:278
 ____fput+0x37/0x40 fs/file_table.c:309
 task_work_run+0x22e/0x2b0 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+0xdb/0x700 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: 0033:0x401540
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 ed 22 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:00007fffbb917ce8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000401540
RDX: 0000000000000000 RSI: 0000000020000100 RDI: 0000000000000003
RBP: 00000000006cc018 R08: 0000000000000100 R09: 0000000000000100
R10: 0000000000000100 R11: 0000000000000246 R12: 0000000000000000
R13: 00000000004024e0 R14: 0000000000000000 R15: 0000000000000000

Local variable description: ----buf.i@igmp_group_dropped
Variable was created at:
 igmp_group_dropped+0x49/0x1280 net/ipv4/igmp.c:1253
 ip_mc_down+0x1d9/0x3e0 net/ipv4/igmp.c:1712
==================================================================

All crashes (12):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	Maintainers
ci-upstream-kmsan-gce	2018/09/16 11:21	https://github.com/google/kmsan.git/master	5815ca49	a343a400	.config	log	report	syz	C	davem@davemloft.net, edumazet@google.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, sunlw.fnst@cn.fujitsu.com
ci-upstream-kmsan-gce	2018/10/01 11:06	https://github.com/google/kmsan.git/master	2b752aff	48a50c6b	.config	log	report	syz	C	davem@davemloft.net, edumazet@google.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, sunlw.fnst@cn.fujitsu.com
ci-upstream-kmsan-gce	2018/10/01 10:29	https://github.com/google/kmsan.git/master	2b752aff	48a50c6b	.config	log	report	syz	C	davem@davemloft.net, edumazet@google.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, sunlw.fnst@cn.fujitsu.com
ci-upstream-kmsan-gce	2018/09/28 12:00	https://github.com/google/kmsan.git/master	23005322	8bb1f0fc	.config	log	report	syz	C	davem@davemloft.net, edumazet@google.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, sunlw.fnst@cn.fujitsu.com
ci-upstream-kmsan-gce	2018/09/16 07:32	https://github.com/google/kmsan.git/master	5815ca49	a343a400	.config	log	report			davem@davemloft.net, edumazet@google.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, sunlw.fnst@cn.fujitsu.com
ci-upstream-kmsan-gce	2018/10/13 10:54	https://github.com/google/kmsan.git/master	22ec98c3	caf12900	.config	log	report			davem@davemloft.net, edumazet@google.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, sunlw.fnst@cn.fujitsu.com
ci-upstream-kmsan-gce	2018/10/02 15:18	https://github.com/google/kmsan.git/master	b2efdb2e	a316a2af	.config	log	report			davem@davemloft.net, edumazet@google.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, sunlw.fnst@cn.fujitsu.com
ci-upstream-kmsan-gce	2018/09/27 18:28	https://github.com/google/kmsan.git/master	a5bff9bd	0c2fa87b	.config	log	report			davem@davemloft.net, edumazet@google.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, sunlw.fnst@cn.fujitsu.com
ci-upstream-kmsan-gce	2018/09/26 09:36	https://github.com/google/kmsan.git/master	eb2e6759	455b6354	.config	log	report			davem@davemloft.net, edumazet@google.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, sunlw.fnst@cn.fujitsu.com
ci-upstream-kmsan-gce	2018/09/25 06:15	https://github.com/google/kmsan.git/master	f94b97e3	0e7547d7	.config	log	report			davem@davemloft.net, edumazet@google.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, sunlw.fnst@cn.fujitsu.com
ci-upstream-kmsan-gce	2018/09/16 13:03	https://github.com/google/kmsan.git/master	5815ca49	a343a400	.config	log	report			davem@davemloft.net, edumazet@google.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, sunlw.fnst@cn.fujitsu.com
ci-upstream-kmsan-gce	2018/09/16 07:32	https://github.com/google/kmsan.git/master	5815ca49	a343a400	.config	log	report			davem@davemloft.net, edumazet@google.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, sunlw.fnst@cn.fujitsu.com