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

write to 0xffff8880b1233124 of 4 bytes by task 22012 on cpu 0:
 get_signal+0x7c7/0x1320 kernel/signal.c:2714
 do_signal+0x3b/0xbf0 arch/x86/kernel/signal.c:815
 exit_to_usermode_loop+0x250/0x2c0 arch/x86/entry/common.c:159
 prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
 do_syscall_64+0x353/0x370 arch/x86/entry/common.c:300
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880b1233124 of 4 bytes by task 22008 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+0x67c/0x18f0 kernel/exit.c:838
 do_group_exit+0xb4/0x1c0 kernel/exit.c:921
 get_signal+0x2a2/0x1320 kernel/signal.c:2734
 do_signal+0x3b/0xbf0 arch/x86/kernel/signal.c:815
 exit_to_usermode_loop+0x250/0x2c0 arch/x86/entry/common.c:159
 prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
 do_syscall_64+0x353/0x370 arch/x86/entry/common.c:300
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 22008 Comm: syz-executor.3 Not tainted 5.4.0-rc6+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 22008 Comm: syz-executor.3 Not tainted 5.4.0-rc6+ #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+0xf5/0x159 lib/dump_stack.c:113
 panic+0x210/0x640 kernel/panic.c:221
 kcsan_report.cold+0xc/0xe kernel/kcsan/report.c:302
 kcsan_setup_watchpoint+0x3fe/0x410 kernel/kcsan/core.c:357
 check_access kernel/kcsan/core.c:409 [inline]
 __tsan_read4+0x145/0x1f0 kernel/kcsan/core.c:529
 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+0x67c/0x18f0 kernel/exit.c:838
 do_group_exit+0xb4/0x1c0 kernel/exit.c:921
 get_signal+0x2a2/0x1320 kernel/signal.c:2734
 do_signal+0x3b/0xbf0 arch/x86/kernel/signal.c:815
 exit_to_usermode_loop+0x250/0x2c0 arch/x86/entry/common.c:159
 prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
 do_syscall_64+0x353/0x370 arch/x86/entry/common.c:300
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45a219
Code: Bad RIP value.
RSP: 002b:00007fa7422adc78 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: fffffffffffffe00 RBX: 0000000000000005 RCX: 000000000045a219
RDX: 04000000000000be RSI: 0000000020008880 RDI: 0000000000000007
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fa7422ae6d4
R13: 00000000004c7cda R14: 00000000004dde58 R15: 00000000ffffffff
Kernel Offset: disabled
Rebooting in 86400 seconds..