==================================================================
BUG: KCSAN: data-race in find_alive_thread / get_signal

read to 0xffff88812a8140a4 of 4 bytes by task 21007 on cpu 1:
 find_alive_thread+0xdd/0x130 kernel/exit.c:495
 find_new_reaper kernel/exit.c:548 [inline]
 forget_original_parent kernel/exit.c:623 [inline]
 exit_notify kernel/exit.c:656 [inline]
 do_exit+0x65c/0x18c0 kernel/exit.c:818
 do_group_exit+0xb4/0x1c0 kernel/exit.c:895
 __do_sys_exit_group kernel/exit.c:906 [inline]
 __se_sys_exit_group kernel/exit.c:904 [inline]
 __x64_sys_exit_group+0x2e/0x30 kernel/exit.c:904
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff88812a8140a4 of 4 bytes by task 21006 on cpu 0:
 get_signal+0x7c7/0x1320 kernel/signal.c:2714
 do_signal+0x2f/0x6c0 arch/x86/kernel/signal.c:815
 exit_to_usermode_loop+0x250/0x2c0 arch/x86/entry/common.c:160
 prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:278 [inline]
 do_syscall_64+0x384/0x3a0 arch/x86/entry/common.c:304
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 21006 Comm: syz-executor.4 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 21006 Comm: syz-executor.4 Not tainted 5.5.0-rc1-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+0x11d/0x181 lib/dump_stack.c:118
 panic+0x210/0x640 kernel/panic.c:221
 kcsan_report.cold+0xc/0xd kernel/kcsan/report.c:313
 kcsan_setup_watchpoint+0x3fe/0x460 kernel/kcsan/core.c:416
 check_access kernel/kcsan/core.c:459 [inline]
 __tsan_unaligned_write4+0xc7/0x110 kernel/kcsan/core.c:588
 get_signal+0x7c7/0x1320 kernel/signal.c:2714
 do_signal+0x2f/0x6c0 arch/x86/kernel/signal.c:815
 exit_to_usermode_loop+0x250/0x2c0 arch/x86/entry/common.c:160
 prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:278 [inline]
 do_syscall_64+0x384/0x3a0 arch/x86/entry/common.c:304
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45d2e9
Code: ff 48 85 f6 0f 84 d7 8c fb ff 48 83 ee 10 48 89 4e 08 48 89 3e 48 89 d7 4c 89 c2 4d 89 c8 4c 8b 54 24 08 b8 38 00 00 00 0f 05 <48> 85 c0 0f 8c ae 8c fb ff 74 01 c3 31 ed 48 f7 c7 00 00 01 00 75
RSP: 002b:00007fff4913f478 EFLAGS: 00000202 ORIG_RAX: 0000000000000038
RAX: 000000000000016b RBX: 00007fc748977700 RCX: 000000000045d2e9
RDX: 00007fc7489779d0 RSI: 00007fc748976db0 RDI: 00000000003d0f00
RBP: 00007fff4913f690 R08: 00007fc748977700 R09: 00007fc748977700
R10: 00007fc7489779d0 R11: 0000000000000202 R12: 0000000000000000
R13: 00007fff4913f52f R14: 00007fc7489779c0 R15: 000000000075bfd4
Kernel Offset: disabled
Rebooting in 86400 seconds..