syzbot

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BUG: KCSAN: data-race in __dentry_kill / __follow_mount_rcu.isra.0

write to 0xffff8881256c3840 of 4 bytes by task 7773 on cpu 1:
 dentry_unlist fs/dcache.c:519 [inline]
 __dentry_kill+0x127/0x3b0 fs/dcache.c:575
 dentry_kill fs/dcache.c:698 [inline]
 dput+0x399/0x700 fs/dcache.c:859
 do_unlinkat+0x34e/0x550 fs/namei.c:4139
 __do_sys_unlink fs/namei.c:4184 [inline]
 __se_sys_unlink fs/namei.c:4182 [inline]
 __x64_sys_unlink+0x38/0x50 fs/namei.c:4182
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881256c3840 of 4 bytes by task 4026 on cpu 0:
 managed_dentry_rcu fs/namei.c:1381 [inline]
 __follow_mount_rcu.isra.0+0x5a/0x330 fs/namei.c:1398
 lookup_fast+0x249/0x6e0 fs/namei.c:1700
 walk_component+0x73/0x9a0 fs/namei.c:1911
 lookup_last fs/namei.c:2391 [inline]
 path_lookupat.isra.0+0x129/0x2e0 fs/namei.c:2436
 filename_lookup+0x145/0x2b0 fs/namei.c:2466
 user_path_at_empty+0x47/0x60 fs/namei.c:2746
 do_readlinkat+0x89/0x230 fs/stat.c:409
 __do_sys_readlink fs/stat.c:442 [inline]
 __se_sys_readlink fs/stat.c:439 [inline]
 __x64_sys_readlink+0x4c/0x60 fs/stat.c:439
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 4026 Comm: udevd Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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