syzbot

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BUG: KCSAN: data-race in __d_lookup_rcu / __d_rehash

read to 0xffff8881013da610 of 8 bytes by task 25063 on cpu 1:
 hlist_bl_unhashed include/linux/list_bl.h:54 [inline]
 d_unhashed include/linux/dcache.h:342 [inline]
 __d_lookup_rcu+0x13f/0x3e0 fs/dcache.c:2322
 lookup_fast+0xc1/0x360 fs/namei.c:1580
 walk_component+0x6d/0x360 fs/namei.c:1966
 link_path_walk+0x56b/0x930
 path_openat+0x1a7/0x1eb0 fs/namei.c:3555
 do_filp_open+0x105/0x220 fs/namei.c:3586
 do_sys_openat2+0xb5/0x2b0 fs/open.c:1212
 do_sys_open fs/open.c:1228 [inline]
 __do_sys_openat fs/open.c:1244 [inline]
 __se_sys_openat fs/open.c:1239 [inline]
 __x64_sys_openat+0xef/0x110 fs/open.c:1239
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

write to 0xffff8881013da610 of 8 bytes by task 25062 on cpu 0:
 hlist_bl_add_head_rcu include/linux/rculist_bl.h:81 [inline]
 __d_rehash+0xb9/0x1f0 fs/dcache.c:2519
 __d_add+0x345/0x450 fs/dcache.c:2713
 d_splice_alias+0xd9/0x460 fs/dcache.c:3100
 proc_pid_instantiate+0xfe/0x120 fs/proc/base.c:3366
 proc_pid_lookup+0x123/0x1c0 fs/proc/base.c:3397
 proc_root_lookup+0x1b/0x40 fs/proc/root.c:322
 __lookup_slow+0x182/0x250 fs/namei.c:1657
 lookup_slow fs/namei.c:1674 [inline]
 walk_component+0x2b6/0x360 fs/namei.c:1970
 link_path_walk+0x56b/0x930
 path_openat+0x1a7/0x1eb0 fs/namei.c:3555
 do_filp_open+0x105/0x220 fs/namei.c:3586
 do_sys_openat2+0xb5/0x2b0 fs/open.c:1212
 do_sys_open fs/open.c:1228 [inline]
 __do_sys_openat fs/open.c:1244 [inline]
 __se_sys_openat fs/open.c:1239 [inline]
 __x64_sys_openat+0xef/0x110 fs/open.c:1239
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 25062 Comm: syz-executor.1 Not tainted 5.16.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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