==================================================================
BUG: KMSAN: uninit-value in memcmp+0x11d/0x180 lib/string.c:863
CPU: 1 PID: 7060 Comm: syz-executor6 Not tainted 4.19.0-rc1+ #40
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
 igmp6_group_dropped+0x2c5/0x12e0 net/ipv6/mcast.c:712
 ipv6_mc_down+0xc8/0x360 net/ipv6/mcast.c:2542
 addrconf_ifdown+0x21bb/0x2670 net/ipv6/addrconf.c:3784
 addrconf_notify+0x2ac/0x5be0 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:1734 [inline]
 call_netdevice_notifiers net/core/dev.c:1752 [inline]
 dev_close_many+0x627/0x9e0 net/core/dev.c:1504
 rollback_registered_many+0x9eb/0x2040 net/core/dev.c:7930
 rollback_registered net/core/dev.c:7995 [inline]
 unregister_netdevice_queue+0x547/0xa40 net/core/dev.c:9039
 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: 0033:0x457099
Code: fd b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 cb b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fe1750bcc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 00007fe1750bd6d4 RCX: 0000000000457099
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00000000009300a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004cb8c0 R14: 00000000004ee8f2 R15: 0000000000000000

Local variable description: ----buf@igmp6_group_dropped
Variable was created at:
 igmp6_group_dropped+0x49/0x12e0 net/ipv6/mcast.c:700
 ipv6_mc_down+0xc8/0x360 net/ipv6/mcast.c:2542
==================================================================