syzbot

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BUG: KCSAN: data-race in __d_instantiate / dput

read-write to 0xffff8881077e2480 of 4 bytes by task 19780 on cpu 0:
 __d_instantiate+0x2cd/0x3b0 fs/dcache.c:2010
 d_instantiate+0x59/0x80 fs/dcache.c:2035
 shmem_symlink+0x364/0x390 mm/shmem.c:3519
 vfs_symlink+0xc2/0x1a0 fs/namei.c:4464
 do_symlinkat+0xe3/0x340 fs/namei.c:4490
 __do_sys_symlink fs/namei.c:4511 [inline]
 __se_sys_symlink fs/namei.c:4509 [inline]
 __x64_sys_symlink+0x56/0x60 fs/namei.c:4509
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff8881077e2480 of 4 bytes by task 2780 on cpu 1:
 fast_dput fs/dcache.c:774 [inline]
 dput+0x35/0x1f0 fs/dcache.c:900
 handle_mounts fs/namei.c:1555 [inline]
 step_into+0x21a/0x800 fs/namei.c:1840
 walk_component+0x164/0x230 fs/namei.c:2008
 lookup_last fs/namei.c:2459 [inline]
 path_lookupat+0x10a/0x2a0 fs/namei.c:2483
 filename_lookup+0x126/0x300 fs/namei.c:2512
 user_path_at_empty+0x42/0x110 fs/namei.c:2911
 do_readlinkat+0x92/0x210 fs/stat.c:494
 __do_sys_readlink fs/stat.c:527 [inline]
 __se_sys_readlink fs/stat.c:524 [inline]
 __x64_sys_readlink+0x47/0x50 fs/stat.c:524
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x00000008 -> 0x00600008

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 2780 Comm: udevd Not tainted 6.7.0-rc6-syzkaller-00022-g55cb5f43689d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
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