==================================================================
BUG: KCSAN: data-race in complete_signal / do_group_exit

write to 0xffff88813655fbf4 of 4 bytes by task 16004 on cpu 0:
 complete_signal+0x4a5/0x600 kernel/signal.c:1084
 __send_signal+0x680/0x760 kernel/signal.c:1221
 send_signal+0x281/0x390 kernel/signal.c:1284
 do_send_sig_info kernel/signal.c:1333 [inline]
 send_sig_info+0xb5/0x100 kernel/signal.c:1648
 send_sig+0x2b/0x30 kernel/signal.c:1658
 pipe_write+0x8a6/0xca0 fs/pipe.c:470
 call_write_iter include/linux/fs.h:2114 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x69d/0x770 fs/read_write.c:605
 ksys_write+0xce/0x180 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:667
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88813655fbf4 of 4 bytes by task 15997 on cpu 1:
 signal_group_exit include/linux/sched/signal.h:269 [inline]
 do_group_exit+0x51/0x1a0 kernel/exit.c:906
 __do_sys_exit_group+0xb/0x10 kernel/exit.c:934
 __se_sys_exit_group+0x5/0x10 kernel/exit.c:932
 __x64_sys_exit_group+0x16/0x20 kernel/exit.c:932
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000000 -> 0x00000004

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 15997 Comm: syz-executor.0 Not tainted 5.13.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================