bisecting fixing commit since 174651bdf802a2139065e8e31ce950e2f3fc4a94
building syzkaller on f879db37f90dcefb681897d2e486c11d8298cb72
testing commit 174651bdf802a2139065e8e31ce950e2f3fc4a94 with gcc (GCC) 8.1.0
kernel signature: 79eed088c30a953b5a7d8f12dced31e4df4dff35
all runs: crashed: WARNING in task_participate_group_stop
testing current HEAD c7ecf3e3a71c216327980f26b1e895ce9b07ad31
testing commit c7ecf3e3a71c216327980f26b1e895ce9b07ad31 with gcc (GCC) 8.1.0
kernel signature: 4a5eff5a6685900cca1bec40c42c218f6de7d64c
run #0: crashed: WARNING in task_participate_group_stop
run #1: crashed: WARNING in task_participate_group_stop
run #2: crashed: WARNING in task_participate_group_stop
run #3: crashed: WARNING in task_participate_group_stop
run #4: crashed: WARNING in task_participate_group_stop
run #5: crashed: WARNING in task_participate_group_stop
run #6: crashed: WARNING in task_participate_group_stop
run #7: crashed: WARNING in task_participate_group_stop
run #8: OK
run #9: OK
revisions tested: 2, total time: 31m11.394687078s (build: 17m17.192668479s, test: 13m8.238290088s)
the crash still happens on HEAD
commit msg: Linux 4.19.92
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
WARNING: CPU: 1 PID: 7924 at kernel/signal.c:367 task_participate_group_stop+0x196/0x1f0 kernel/signal.c:360
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 7924 Comm: 3 Not tainted 4.19.92-syzkaller #0
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+0x123/0x177 lib/dump_stack.c:118
 panic+0x1cd/0x375 kernel/panic.c:186
 __warn.cold.8+0x1b/0x3e kernel/panic.c:541
 report_bug+0x1a4/0x200 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:178 [inline]
 do_error_trap+0x200/0x350 arch/x86/kernel/traps.c:296
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:1037
RIP: 0010:task_participate_group_stop+0x196/0x1f0 kernel/signal.c:367
Code: 83 c2 03 38 ca 7c 04 84 c9 75 61 41 89 84 24 a4 00 00 00 48 83 c4 08 b8 01 00 00 00 5b 41 5c 41 5d 5d c3 0f 0b e9 e1 fe ff ff <0f> 0b e9 30 ff ff ff 48 89 df e8 eb 7d 55 00 e9 08 ff ff ff e8 01
RSP: 0018:ffff888080507bd0 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff888096280220 RCX: ffffffff814bd7f1
RDX: 1ffff11012c50044 RSI: 0000000000000016 RDI: ffff88808f276200
RBP: ffff888080507bf0 R08: ffffed101257a93a R09: ffffed101257a939
R10: ffffed101257a939 R11: ffff888092bd49cb R12: ffff888096280180
R13: 0000000000040000 R14: dffffc0000000000 R15: ffff888080507f58
kobject: 'loop3' (00000000bd7bca5c): kobject_uevent_env
 do_signal_stop+0x186/0x6a0 kernel/signal.c:2266
 get_signal+0xafd/0x1a00 kernel/signal.c:2453
 do_signal+0x87/0x1960 arch/x86/kernel/signal.c:821
 exit_to_usermode_loop+0x114/0x200 arch/x86/entry/common.c:163
 prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:271 [inline]
 do_syscall_64+0x413/0x4e0 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x324
Code: Bad RIP value.
RSP: 002b:00007ffdc780c8d0 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..