syzbot

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BUG: KCSAN: data-race in __d_instantiate / dput

read-write to 0xffff888109b266c0 of 4 bytes by task 3216 on cpu 1:
 __d_instantiate+0x2cd/0x3b0 fs/dcache.c:2011
 d_instantiate+0x59/0x80 fs/dcache.c:2036
 shmem_symlink+0x329/0x370 mm/shmem.c:3183
 vfs_symlink+0xc2/0x1a0 fs/namei.c:4398
 do_symlinkat+0xe3/0x320 fs/namei.c:4424
 __do_sys_symlink fs/namei.c:4445 [inline]
 __se_sys_symlink fs/namei.c:4443 [inline]
 __x64_sys_symlink+0x56/0x60 fs/namei.c:4443
 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 0xffff888109b266c0 of 4 bytes by task 2744 on cpu 0:
 fast_dput fs/dcache.c:774 [inline]
 dput+0x35/0x1f0 fs/dcache.c:900
 handle_mounts fs/namei.c:1549 [inline]
 step_into+0x21a/0x800 fs/namei.c:1832
 walk_component+0x164/0x230 fs/namei.c:2000
 lookup_last fs/namei.c:2451 [inline]
 path_lookupat+0x10a/0x2a0 fs/namei.c:2475
 filename_lookup+0x126/0x300 fs/namei.c:2504
 user_path_at_empty+0x42/0x110 fs/namei.c:2877
 do_readlinkat+0x92/0x210 fs/stat.c:477
 __do_sys_readlink fs/stat.c:510 [inline]
 __se_sys_readlink fs/stat.c:507 [inline]
 __x64_sys_readlink+0x47/0x50 fs/stat.c:507
 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: 0x00000008 -> 0x00600008

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 2744 Comm: udevd Not tainted 6.3.0-rc1-syzkaller-00230-gef5f68cc1f82 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
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