bisecting fixing commit since fbc5fe7a54d02e11972e3b2a5ddb6ffc88162c8f
building syzkaller on f879db37f90dcefb681897d2e486c11d8298cb72
testing commit fbc5fe7a54d02e11972e3b2a5ddb6ffc88162c8f with gcc (GCC) 8.1.0
kernel signature: 11b258e859e38c7f284e7028eb81182b2841fdb30966663b0d7846bdae8bd380
all runs: crashed: WARNING in task_participate_group_stop
testing current HEAD 78d697fc93f98054e36a3ab76dca1a88802ba7be
testing commit 78d697fc93f98054e36a3ab76dca1a88802ba7be with gcc (GCC) 8.1.0
kernel signature: 19d985a37767216fcb850545180a30ff4bc45bc960d298ef02ce61c0e4547e67
all runs: crashed: WARNING in task_participate_group_stop
revisions tested: 2, total time: 23m39.082607768s (build: 16m42.178784971s, test: 6m22.093141722s)
the crash still happens on HEAD
commit msg: Linux 4.14.172
crash: WARNING in task_participate_group_stop
IPv6: ADDRCONF(NETDEV_UP): vxcan1: link is not ready
IPv6: ADDRCONF(NETDEV_CHANGE): vxcan1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): vxcan0: link becomes ready
8021q: adding VLAN 0 to HW filter on device batadv0
------------[ cut here ]------------
WARNING: CPU: 0 PID: 7699 at kernel/signal.c:358 task_participate_group_stop+0x192/0x1f0 kernel/signal.c:351
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 7699 Comm: 3 Not tainted 4.14.172-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
 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:963
RIP: 0010:task_participate_group_stop+0x192/0x1f0 kernel/signal.c:358
RSP: 0018:ffff88809fd4fba8 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff888094a312d8 RCX: 1ffff1100fd595ec
RDX: 1ffff1101294625b RSI: 0000000000000016 RDI: ffff88807eaca6c0
RBP: ffff88809fd4fbc8 R08: ffff88807eacaf60 R09: 0000000000005aab
R10: 0000000000000000 R11: ffff88807eaca6c0 R12: ffff888094a31240
R13: 0000000000040000 R14: ffff88809fd4ff58 R15: dffffc0000000000
 do_signal_stop+0x186/0x690 kernel/signal.c:2107
 get_signal+0xb74/0x1b30 kernel/signal.c:2293
 do_signal+0x7f/0x19a0 arch/x86/kernel/signal.c:814
 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+0x42/0xb7
RIP: 0033:0x324
RSP: 002b:00007ffc163fee70 EFLAGS: 00000200 ORIG_RAX: 000000000000003b
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..