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BUG: KCSAN: data-race in exit_signals / task_dump_owner

write to 0xffff88809efaa024 of 4 bytes by task 19473 on cpu 0:
 exit_signals+0x124/0x580 kernel/signal.c:2831
 do_exit+0x19a/0x16a0 kernel/exit.c:762
 do_group_exit+0x17a/0x180 kernel/exit.c:903
 __do_sys_exit_group+0xb/0x10 kernel/exit.c:914
 __se_sys_exit_group+0x5/0x10 kernel/exit.c:912
 __x64_sys_exit_group+0x16/0x20 kernel/exit.c:912
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88809efaa024 of 4 bytes by task 19476 on cpu 1:
 task_dump_owner+0x2b/0x1b0 fs/proc/base.c:1809
 pid_update_inode fs/proc/base.c:1951 [inline]
 pid_revalidate+0x69/0x110 fs/proc/base.c:1974
 lookup_fast+0x208/0x370 fs/namei.c:768
 walk_component+0x5c/0x350 fs/namei.c:1856
 link_path_walk+0x462/0x730 fs/namei.c:2179
 path_openat+0x199/0x20c0 fs/namei.c:3356
 do_filp_open+0xbd/0x1d0 fs/namei.c:3387
 do_sys_openat2+0x33b/0x500 fs/open.c:1174
 do_sys_open fs/open.c:1190 [inline]
 __do_sys_open fs/open.c:1198 [inline]
 __se_sys_open fs/open.c:1194 [inline]
 __x64_sys_open+0xe2/0x110 fs/open.c:1194
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 19476 Comm: syz-executor.0 Not tainted 5.8.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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