syzbot

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BUG: KCSAN: data-race in __d_lookup / __d_rehash

write to 0xffff8881066b0cd0 of 8 bytes by task 19818 on cpu 0:
 hlist_bl_add_head_rcu include/linux/rculist_bl.h:81 [inline]
 __d_rehash+0xc4/0x220 fs/dcache.c:2579
 __d_add+0x36d/0x4a0 fs/dcache.c:2794
 d_splice_alias+0xd6/0x270 fs/dcache.c:3182
 ext4_lookup+0x199/0x390 fs/ext4/namei.c:1863
 lookup_one_qstr_excl+0xc0/0x180 fs/namei.c:1605
 filename_create+0x14d/0x2b0 fs/namei.c:3885
 do_symlinkat+0x84/0x320 fs/namei.c:4494
 __do_sys_symlinkat fs/namei.c:4517 [inline]
 __se_sys_symlinkat fs/namei.c:4514 [inline]
 __x64_sys_symlinkat+0x62/0x70 fs/namei.c:4514
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff8881066b0cd0 of 8 bytes by task 2745 on cpu 1:
 hlist_bl_unhashed include/linux/list_bl.h:54 [inline]
 d_unhashed include/linux/dcache.h:335 [inline]
 __d_lookup+0x10e/0x380 fs/dcache.c:2491
 lookup_fast+0x4c/0x290 fs/namei.c:1648
 walk_component fs/namei.c:1994 [inline]
 link_path_walk+0x3f4/0x7e0 fs/namei.c:2325
 path_openat+0x19b/0x1d00 fs/namei.c:3787
 do_filp_open+0xf6/0x200 fs/namei.c:3818
 do_sys_openat2+0xb5/0x2a0 fs/open.c:1356
 do_sys_open fs/open.c:1372 [inline]
 __do_sys_openat fs/open.c:1388 [inline]
 __se_sys_openat fs/open.c:1383 [inline]
 __x64_sys_openat+0xf3/0x120 fs/open.c:1383
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0xffff888237835ac8 -> 0xffff8881749ffe48

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 2745 Comm: udevd Tainted: G        W          6.3.0-syzkaller-11301-g1ae78a14516b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023
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