bisecting fixing commit since 54b4fa6d39551639cb10664f6ac78b01993a1d7e
building syzkaller on 05736b290dd5af17adbb0fb5ea67405a0167a7c8
testing commit 54b4fa6d39551639cb10664f6ac78b01993a1d7e with gcc (GCC) 8.1.0
kernel signature: 2bc3b79c0cfc4ea7d31ad3df66f42ae436d5b6af26160b6fd6caae7ceb4487d0
run #0: crashed: WARNING in task_participate_group_stop
run #1: OK
run #2: OK
run #3: OK
run #4: OK
run #5: OK
run #6: OK
run #7: OK
run #8: OK
run #9: OK
testing current HEAD 7edd66cf61670d2d0c31f89cb3a247016e489a8a
testing commit 7edd66cf61670d2d0c31f89cb3a247016e489a8a with gcc (GCC) 8.1.0
kernel signature: edf240096449b570de691b70fa06c7cec623d9cbaf9a9990668d56bab9c5abb2
run #0: crashed: WARNING in task_participate_group_stop
run #1: OK
run #2: OK
run #3: OK
run #4: OK
run #5: crashed: WARNING in task_participate_group_stop
run #6: OK
run #7: OK
run #8: OK
run #9: crashed: WARNING in task_participate_group_stop
revisions tested: 2, total time: 41m36.437094897s (build: 18m24.009895361s, test: 22m28.040996752s)
the crash still happens on HEAD
commit msg: Linux 4.19.118
crash: WARNING in task_participate_group_stop
IPVS: ftp: loaded support on port[0] = 21
IPVS: ftp: loaded support on port[0] = 21
IPVS: ftp: loaded support on port[0] = 21
cgroup: fork rejected by pids controller in /system.slice/ssh.service
WARNING: CPU: 0 PID: 3747 at kernel/signal.c:372 task_participate_group_stop+0x196/0x1f0 kernel/signal.c:365
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 3747 Comm: file0 Not tainted 4.19.118-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:372
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 5b 9c 55 00 e9 08 ff ff ff e8 71
RSP: 0018:ffff888051567bd0 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff888088077960 RCX: ffffffff814bbfb0
RDX: 1ffff1101100ef2c RSI: 0000000000000016 RDI: ffff88808bb5c440
RBP: ffff888051567bf0 R08: ffffed1014079e2a R09: ffffed1014079e29
R10: ffffed1014079e29 R11: ffff8880a03cf14b R12: ffff8880880778c0
R13: 0000000000040000 R14: dffffc0000000000 R15: ffff888051567f58
 do_signal_stop+0x186/0x6a0 kernel/signal.c:2276
 get_signal+0xafd/0x1a00 kernel/signal.c:2463
 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: 0033:0x447c69
Code: Bad RIP value.
RSP: 002b:00007fb568669d98 EFLAGS: 00000246 ORIG_RAX: 000000000000000b
RAX: ffffffffffffffea RBX: 00000000006e39f8 RCX: 0000000000447c69
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000200000c0
RBP: 00000000006e39f0 R08: 00007fb56866a700 R09: 0000000000000000
R10: 00007fb56866a700 R11: 0000000000000246 R12: 00000000006e39fc
R13: 0000000000000000 R14: 07007ff8464c457f R15: 000000000000f172
Kernel Offset: disabled
Rebooting in 86400 seconds..