WARNING in batadv_mcast_mla_tt_retract

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: c98875d9 Linux 4.19.36
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=105c0403200000
kernel config: https://syzkaller.appspot.com/x/.config?x=5e40ac5fbcc6366d
dashboard link: https://syzkaller.appspot.com/bug?extid=00102ab90ea4d4c92f9b
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+00102a...@syzkaller.appspotmail.com

IPv6: ADDRCONF(NETDEV_UP): bridge_slave_1: link is not ready
device hsr_slave_0 entered promiscuous mode
device hsr_slave_1 entered promiscuous mode
IPv6: ADDRCONF(NETDEV_UP): hsr_slave_0: link is not ready
IPv6: ADDRCONF(NETDEV_UP): hsr_slave_1: link is not ready
WARNING: CPU: 1 PID: 23 at net/batman-adv/multicast.c:337
batadv_mcast_mla_tt_retract+0x309/0x3d0 net/batman-adv/multicast.c:337
IPv6: ADDRCONF(NETDEV_UP): bridge0: link is not ready
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 23 Comm: kworker/u4:1 Not tainted 4.19.36 #4
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
kobject: 'vcan0' (0000000007db1923): kobject_add_internal: parent: 'net',
set: 'devices'
Workqueue: bat_events batadv_mcast_mla_update
kobject: 'vcan0' (0000000007db1923): kobject_uevent_env
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
panic+0x263/0x51d kernel/panic.c:185
__warn.cold+0x20/0x54 kernel/panic.c:540
report_bug+0x263/0x2b0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
fixup_bug arch/x86/kernel/traps.c:173 [inline]
do_error_trap+0x204/0x360 arch/x86/kernel/traps.c:296
kobject: 'vcan0' (0000000007db1923): fill_kobj_path: path
= '/devices/virtual/net/vcan0'
kobject: 'queues' (00000000c0682d91): kobject_add_internal:
parent: 'vcan0', set: '<NULL>'
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
kobject: 'queues' (00000000c0682d91): kobject_uevent_env
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:997
kobject: 'queues' (00000000c0682d91): kobject_uevent_env: filter function
caused the event to drop!
RIP: 0010:batadv_mcast_mla_tt_retract+0x309/0x3d0
net/batman-adv/multicast.c:337
kobject: 'rx-0' (000000002f70c722): kobject_add_internal: parent: 'queues',
set: 'queues'
Code: cd 56 98 fa 4c 8b 7d c0 4d 85 ff 0f 85 c3 fd ff ff e8 bb 56 98 fa 48
83 c4 38 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 a7 56 98 fa <0f> 0b e9 54 fd
ff ff e8 eb b7 ce fa e9 37 fe ff ff 48 89 df e8 fe
kobject: 'rx-0' (000000002f70c722): kobject_uevent_env
RSP: 0018:ffff8880aa39fb50 EFLAGS: 00010293
RAX: ffff8880aa392600 RBX: 0000000000000001 RCX: ffffffff86d2ebbb
RDX: 0000000000000000 RSI: ffffffff86d2ee69 RDI: 0000000000000007
RBP: ffff8880aa39fbb0 R08: ffff8880aa392600 R09: 0000000000000002
R10: ffffed1015d24732 R11: ffff8880ae923993 R12: ffff8880aa39fc98
R13: ffff888081138bd0 R14: 0000000000000000 R15: ffff8880aa39fd08
kobject: 'rx-0' (000000002f70c722): fill_kobj_path: path
= '/devices/virtual/net/vcan0/queues/rx-0'
__batadv_mcast_mla_update net/batman-adv/multicast.c:635 [inline]
batadv_mcast_mla_update+0x553/0x1ec0 net/batman-adv/multicast.c:661
process_one_work+0x98e/0x1760 kernel/workqueue.c:2153
kobject: 'tx-0' (000000007f187843): kobject_add_internal: parent: 'queues',
set: 'queues'
worker_thread+0x98/0xe40 kernel/workqueue.c:2296
kthread+0x357/0x430 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:413
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.