bisecting fixing commit since 4520f06b03ae667e442da1ab9351fd28cd7ac598
building syzkaller on a8c6a3f8da30ccf825c6001c81a8adff21829c30
testing commit 4520f06b03ae667e442da1ab9351fd28cd7ac598 with gcc (GCC) 8.1.0
kernel signature: 4f4b9cde3d60e27f605013303b8c3eca84441c5a45e762311ba7689cece966a4
all runs: crashed: WARNING in task_participate_group_stop
testing current HEAD c6db52a88798e5a0dfef80041ad4d33cc8cf04eb
testing commit c6db52a88798e5a0dfef80041ad4d33cc8cf04eb with gcc (GCC) 8.1.0
kernel signature: 007b2fa66376a1670be09b46f614a80b1b223b9f002cd77ae97374ccce780870
all runs: crashed: WARNING in task_participate_group_stop
revisions tested: 2, total time: 24m19.287379482s (build: 17m6.895771432s, test: 6m8.336116432s)
the crash still happens on HEAD
commit msg: Linux 4.14.183
crash: WARNING in task_participate_group_stop
IPv6: ADDRCONF(NETDEV_CHANGE): vlan1: link becomes ready
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0
batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems!
------------[ cut here ]------------
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0
WARNING: CPU: 1 PID: 7771 at kernel/signal.c:358 task_participate_group_stop+0x192/0x1f0 kernel/signal.c:351
Kernel panic - not syncing: panic_on_warn set ...

batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems!
CPU: 1 PID: 7771 Comm: file0 Not tainted 4.14.183-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xf7/0x13b lib/dump_stack.c:58
 panic+0x1b0/0x358 kernel/panic.c:183
 __warn.cold.8+0x25/0x2c kernel/panic.c:547
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0
 report_bug+0x1a4/0x1f3 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:177 [inline]
 do_error_trap+0x1bd/0x310 arch/x86/kernel/traps.c:295
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:314
 invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:964
RIP: 0010:task_participate_group_stop+0x192/0x1f0 kernel/signal.c:358
batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems!
RSP: 0018:ffff8880a656fba8 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff8880a54d5218 RCX: 1ffff11014ad61bd
RDX: 1ffff11014a9aa43 RSI: 0000000000000016 RDI: ffff8880a56b0540
RBP: ffff8880a656fbc8 R08: ffff8880a56b0de8 R09: 0000000000005aab
R10: 0000000000000000 R11: ffff8880a56b0540 R12: ffff8880a54d5180
R13: 0000000000040000 R14: ffff8880a656ff58 R15: dffffc0000000000
IPv6: ADDRCONF(NETDEV_UP): batadv_slave_0: link is not ready
 do_signal_stop+0x186/0x690 kernel/signal.c:2112
 get_signal+0xb74/0x1b30 kernel/signal.c:2298
 do_signal+0x7f/0x19a0 arch/x86/kernel/signal.c:814
batman_adv: batadv0: Interface activated: batadv_slave_0
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3e) already exists on: batadv_slave_1
 exit_to_usermode_loop+0x114/0x1b0 arch/x86/entry/common.c:160
 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
 do_syscall_64+0x416/0x5b0 arch/x86/entry/common.c:297
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x45c889
RSP: 002b:00007f3d6db91c78 EFLAGS: 00000246 ORIG_RAX: 000000000000000b
RAX: ffffffffffffffea RBX: 00007f3d6db926d4 RCX: 000000000045c889
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000200000c0
batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems!
RBP: 000000000076bfa0 R08: 0000000000000000 R09: 0000000000000000
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3e) already exists on: batadv_slave_1
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000000a6 R14: 00000000004c33d1 R15: 000000000076bfac
Kernel Offset: disabled
Rebooting in 86400 seconds..