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BUG: KCSAN: data-race in pid_update_inode / proc_fill_cache

read to 0xffff8881251a7588 of 2 bytes by task 18350 on cpu 1:
 proc_fill_cache+0xc6/0x290 fs/proc/base.c:1912
 proc_pid_readdir+0x1c4/0x423 fs/proc/base.c:3349
 proc_root_readdir+0x8f/0xb0 fs/proc/root.c:263
 iterate_dir+0x312/0x380 fs/readdir.c:65
 __do_sys_getdents fs/readdir.c:285 [inline]
 __se_sys_getdents fs/readdir.c:266 [inline]
 __x64_sys_getdents+0x14b/0x280 fs/readdir.c:266
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8881251a7588 of 2 bytes by task 18315 on cpu 0:
 pid_update_inode+0x51/0x70 fs/proc/base.c:1820
 pid_revalidate+0x91/0x120 fs/proc/base.c:1841
 d_revalidate fs/namei.c:758 [inline]
 d_revalidate fs/namei.c:755 [inline]
 lookup_fast+0x6ac/0x6c0 fs/namei.c:1613
 walk_component+0x6d/0xd90 fs/namei.c:1798
 link_path_walk.part.0+0x5d3/0xa90 fs/namei.c:2128
 link_path_walk fs/namei.c:2059 [inline]
 path_openat+0x14f/0x3580 fs/namei.c:3536
 do_filp_open+0x11e/0x1b0 fs/namei.c:3567
 do_sys_open+0x3b3/0x4f0 fs/open.c:1097
 __do_sys_open fs/open.c:1115 [inline]
 __se_sys_open fs/open.c:1110 [inline]
 __x64_sys_open+0x55/0x70 fs/open.c:1110
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 18315 Comm: ps Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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