KCSAN: data-race in __follow_mount_rcu.isra.0 / vfs

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

write to 0xffff8881251c63c0 of 4 bytes by task 4913 on cpu 1:
 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 0xffff8881251c63c0 of 4 bytes by task 4031 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: 4031 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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Crashes (13):
Time	Kernel	Commit	Syzkaller	Config	Log	Report	Manager
2020/04/09 17:27	https://github.com/google/ktsan.git kcsan	40959e34d670	a8c6a3f8	.config	console log	report	ci2-upstream-kcsan-gce
2020/04/09 13:38	https://github.com/google/ktsan.git kcsan	40959e34d670	a8c6a3f8	.config	console log	report	ci2-upstream-kcsan-gce
2020/04/07 05:06	https://github.com/google/ktsan.git kcsan	40959e34d670	99a96044	.config	console log	report	ci2-upstream-kcsan-gce
2020/03/25 23:16	https://github.com/google/ktsan.git kcsan	40959e34d670	e8e6c7d2	.config	console log	report	ci2-upstream-kcsan-gce
2020/03/18 13:47	https://github.com/google/ktsan.git kcsan	941e0d917bbf	0a96a13c	.config	console log	report	ci2-upstream-kcsan-gce
2020/03/10 03:44	https://github.com/google/ktsan.git kcsan	941e0d917bbf	35f53e45	.config	console log	report	ci2-upstream-kcsan-gce
2020/03/08 11:18	https://github.com/google/ktsan.git kcsan	941e0d917bbf	2e9971bb	.config	console log	report	ci2-upstream-kcsan-gce
2020/03/04 17:59	https://github.com/google/ktsan.git kcsan	766d004d1b85	712198ac	.config	console log	report	ci2-upstream-kcsan-gce
2020/02/26 19:30	https://github.com/google/ktsan.git kcsan	766d004d1b85	251aabb7	.config	console log	report	ci2-upstream-kcsan-gce
2020/02/25 09:44	https://github.com/google/ktsan.git kcsan	766d004d1b85	59b57593	.config	console log	report	ci2-upstream-kcsan-gce
2020/02/25 08:10	https://github.com/google/ktsan.git kcsan	766d004d1b85	59b57593	.config	console log	report	ci2-upstream-kcsan-gce
2020/02/25 04:30	https://github.com/google/ktsan.git kcsan	766d004d1b85	59b57593	.config	console log	report	ci2-upstream-kcsan-gce
2020/02/23 07:03	https://github.com/google/ktsan.git kcsan	766d004d1b85	2c36e7a7	.config	console log	report	ci2-upstream-kcsan-gce

Crashes (13):

Time

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