KCSAN: data-race in vfs_unlink / walk

==================================================================
BUG: KCSAN: data-race in vfs_unlink / walk_component

write to 0xffff8881255693c0 of 4 bytes by task 16267 on cpu 0:
 dont_mount include/linux/dcache.h:352 [inline]
 vfs_unlink+0x267/0x3e0 fs/namei.c:4075
 do_unlinkat+0x33f/0x550 fs/namei.c:4137
 __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 0xffff8881255693c0 of 4 bytes by task 4027 on cpu 1:
 d_is_symlink include/linux/dcache.h:419 [inline]
 step_into fs/namei.c:1878 [inline]
 walk_component+0xf1/0x9a0 fs/namei.c:1929
 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: 1 PID: 4027 Comm: udevd Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

Crashes (18):
Time	Kernel	Commit	Syzkaller	Config	Log	Report	Manager
2020/04/13 03:04	https://github.com/google/ktsan.git kcsan	40959e34d670	17a986e5	.config	console log	report	ci2-upstream-kcsan-gce
2020/04/11 05:32	https://github.com/google/ktsan.git kcsan	40959e34d670	a8c6a3f8	.config	console log	report	ci2-upstream-kcsan-gce
2020/04/07 22:28	https://github.com/google/ktsan.git kcsan	40959e34d670	db9bcd4b	.config	console log	report	ci2-upstream-kcsan-gce
2020/04/03 05:47	https://github.com/google/ktsan.git kcsan	40959e34d670	a34e2c33	.config	console log	report	ci2-upstream-kcsan-gce
2020/03/22 22:29	https://github.com/google/ktsan.git kcsan	40959e34d670	78267cec	.config	console log	report	ci2-upstream-kcsan-gce
2020/03/21 13:07	https://github.com/google/ktsan.git kcsan	40959e34d670	aa6c6a55	.config	console log	report	ci2-upstream-kcsan-gce
2020/03/15 15:56	https://github.com/google/ktsan.git kcsan	941e0d917bbf	749688d2	.config	console log	report	ci2-upstream-kcsan-gce
2020/03/08 12:26	https://github.com/google/ktsan.git kcsan	941e0d917bbf	2e9971bb	.config	console log	report	ci2-upstream-kcsan-gce
2020/03/06 08:45	https://github.com/google/ktsan.git kcsan	766d004d1b85	7fb694ef	.config	console log	report	ci2-upstream-kcsan-gce
2020/03/06 07:39	https://github.com/google/ktsan.git kcsan	766d004d1b85	b655d91b	.config	console log	report	ci2-upstream-kcsan-gce
2020/03/02 07:38	https://github.com/google/ktsan.git kcsan	766d004d1b85	4a4e0509	.config	console log	report	ci2-upstream-kcsan-gce
2020/02/27 20:57	https://github.com/google/ktsan.git kcsan	766d004d1b85	c88c7b75	.config	console log	report	ci2-upstream-kcsan-gce
2020/02/26 09:27	https://github.com/google/ktsan.git kcsan	766d004d1b85	4f588111	.config	console log	report	ci2-upstream-kcsan-gce
2020/02/24 18:19	https://github.com/google/ktsan.git kcsan	766d004d1b85	1253d6f0	.config	console log	report	ci2-upstream-kcsan-gce
2020/02/23 06:57	https://github.com/google/ktsan.git kcsan	766d004d1b85	2c36e7a7	.config	console log	report	ci2-upstream-kcsan-gce
2020/02/21 21:25	https://github.com/google/ktsan.git kcsan	766d004d1b85	2ffa6679	.config	console log	report	ci2-upstream-kcsan-gce
2020/02/20 14:22	https://github.com/google/ktsan.git kcsan	b12d66a6c34f	81230308	.config	console log	report	ci2-upstream-kcsan-gce
2020/02/14 23:27	https://github.com/google/ktsan.git kcsan	b12d66a6c34f	5d7b90f1	.config	console log	report	ci2-upstream-kcsan-gce

Crashes (18):

Time

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