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

read to 0xffff888123c1b0a4 of 4 bytes by task 17462 on cpu 0:
 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
 __do_sys_exit_group kernel/exit.c:932 [inline]
 __se_sys_exit_group kernel/exit.c:930 [inline]
 __x64_sys_exit_group+0x2e/0x30 kernel/exit.c:930
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff888123c1b0a4 of 4 bytes by task 17461 on cpu 1:
 get_signal+0x7c7/0x1320 kernel/signal.c:2714
 do_signal+0x3b/0xc00 arch/x86/kernel/signal.c:815
 exit_to_usermode_loop+0x250/0x2c0 arch/x86/entry/common.c:159
 prepare_exit_to_usermode+0x180/0x1a0 arch/x86/entry/common.c:194
 swapgs_restore_regs_and_return_to_usermode+0x0/0x40

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 17461 Comm: syz-executor.5 Not tainted 5.4.0-rc3+ #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: 17461 Comm: syz-executor.5 Not tainted 5.4.0-rc3+ #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/0x10 kernel/kcsan/report.c:302
 __kcsan_setup_watchpoint+0x32e/0x4a0 kernel/kcsan/core.c:411
 __tsan_write4 kernel/kcsan/kcsan.c:35 [inline]
 __tsan_write4+0x32/0x40 kernel/kcsan/kcsan.c:35
 get_signal+0x7c7/0x1320 kernel/signal.c:2714
 do_signal+0x3b/0xc00 arch/x86/kernel/signal.c:815
 exit_to_usermode_loop+0x250/0x2c0 arch/x86/entry/common.c:159
 prepare_exit_to_usermode+0x180/0x1a0 arch/x86/entry/common.c:194
 retint_user+0x8/0x8
RIP: 0033:0x40ef88
Code: 8b 34 c6 4a 8d 04 2e 48 3d ff ff ff 7e 0f 86 77 ff ff ff bf c1 f6 4b 00 31 c0 e8 73 2e ff ff 31 ff e8 bc 2a ff ff 0f 1f 40 00 <89> 3c b5 00 00 73 00 eb b6 31 ed 0f 1f 44 00 00 80 3d 5e 32 66 00
RSP: 002b:00007ffca3ad6d70 EFLAGS: 00010246
RAX: 0000000081006ee2 RBX: 000000004b16861e RCX: 0000001b2d920000
RDX: 0000000000000000 RSI: 0000000000000ee2 RDI: ffffffff81006ee2
RBP: 0000000000000000 R08: 0000000081006ee2 R09: 0000000081006ee6
R10: 00007ffca3ad6f10 R11: 0000000000000246 R12: 000000000075bfa8
R13: 0000000080000000 R14: 00007fe689ed1008 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..