KCSAN: data-race in lookup_fast / retain

KCSAN: data-race in lookup_fast / retain_dentry (4)
Status: auto-closed as invalid on 2021/03/27 05:59
Reported-by: syzbot+@syzkaller.appspotmail.com
First crash: 302d, last: 250d

similar bugs (4):
Kernel	Title	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in lookup_fast / retain_dentry (5)	1	202d	202d	0/22	auto-closed as invalid on 2021/05/17 09:51
upstream	KCSAN: data-race in lookup_fast / retain_dentry	2	435d	447d	0/22	auto-closed as invalid on 2020/09/23 11:25
upstream	KCSAN: data-race in lookup_fast / retain_dentry (2)	1	396d	396d	0/22	auto-closed as invalid on 2020/10/31 17:53
upstream	KCSAN: data-race in lookup_fast / retain_dentry (3)	2	340d	325d	0/22	auto-closed as invalid on 2020/12/27 03:33

Sample crash report:

loop1: detected capacity change from 244 to 0
==================================================================
BUG: KCSAN: data-race in lookup_fast / retain_dentry

write to 0xffff88800ac253c0 of 4 bytes by task 22997 on cpu 1:
 retain_dentry+0x1de/0x260 fs/dcache.c:659
 dput+0x10e/0x420 fs/dcache.c:880
 path_put+0x1b/0x30 fs/namei.c:496
 do_mount fs/namespace.c:3225 [inline]
 __do_sys_mount fs/namespace.c:3432 [inline]
 __se_sys_mount+0x247/0x2e0 fs/namespace.c:3409
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3409
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88800ac253c0 of 4 bytes by task 22989 on cpu 0:
 d_revalidate fs/namei.c:767 [inline]
 lookup_fast+0x15f/0x370 fs/namei.c:1493
 walk_component+0x5c/0x350 fs/namei.c:1857
 lookup_last fs/namei.c:2312 [inline]
 path_lookupat+0x12d/0x560 fs/namei.c:2336
 filename_lookup+0xf2/0x380 fs/namei.c:2369
 user_path_at_empty+0x3b/0x50 fs/namei.c:2649
 user_path_at include/linux/namei.h:59 [inline]
 do_mount fs/namespace.c:3221 [inline]
 __do_sys_mount fs/namespace.c:3432 [inline]
 __se_sys_mount+0x209/0x2e0 fs/namespace.c:3409
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3409
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 22989 Comm: syz-executor.1 Not tainted 5.11.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

Crashes (4):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	VM info	Title
ci2-upstream-kcsan-gce	2021/02/20 05:53	upstream	f40ddce88593	f689d40a	.config	log	report	info	KCSAN: data-race in lookup_fast / retain_dentry
ci2-upstream-kcsan-gce	2021/02/08 00:39	upstream	b75dba7f472c	2ce644fc	.config	log	report	info	KCSAN: data-race in lookup_fast / retain_dentry
ci2-upstream-kcsan-gce	2021/01/28 07:41	upstream	76c057c84d28	eefc07f2	.config	log	report	info	KCSAN: data-race in lookup_fast / retain_dentry
ci2-upstream-kcsan-gce	2020/12/30 15:40	upstream	139711f033f6	ecb8c012	.config	log	report	info