KCSAN: data-race in lookup_fast / shrink_dentry

KCSAN: data-race in lookup_fast / shrink_dentry_list
Status: auto-closed as invalid on 2020/10/08 14:19
Reported-by: syzbot+@syzkaller.appspotmail.com
First crash: 414d, last: 388d

similar bugs (3):
Kernel	Title	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in lookup_fast / shrink_dentry_list (4)	1	180d	180d	0/22	auto-closed as invalid on 2021/05/04 09:30
upstream	KCSAN: data-race in lookup_fast / shrink_dentry_list (2)	1	330d	330d	0/22	auto-closed as invalid on 2020/12/05 11:21
upstream	KCSAN: data-race in lookup_fast / shrink_dentry_list (3)	2	237d	266d	0/22	auto-closed as invalid on 2021/03/08 10:39

Sample crash report:

==================================================================
BUG: KCSAN: data-race in lookup_fast / shrink_dentry_list

write to 0xffff88811ec77240 of 4 bytes by task 1588 on cpu 1:
 shrink_dentry_list+0x127/0x530 fs/dcache.c:421
 shrink_dcache_sb+0x10d/0x1c0 fs/dcache.c:1261
 reconfigure_super+0x267/0x4d0 fs/super.c:940
 do_remount fs/namespace.c:2612 [inline]
 path_mount+0x13c2/0x1c70 fs/namespace.c:3184
 do_mount fs/namespace.c:3205 [inline]
 __do_sys_mount fs/namespace.c:3413 [inline]
 __se_sys_mount+0x126/0x180 fs/namespace.c:3390
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3390
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88811ec77240 of 4 bytes by task 8729 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:1856
 lookup_last fs/namei.c:2309 [inline]
 path_lookupat+0x12d/0x560 fs/namei.c:2333
 filename_lookup+0xf2/0x380 fs/namei.c:2366
 user_path_at_empty+0x3b/0x50 fs/namei.c:2646
 user_path_at include/linux/namei.h:59 [inline]
 vfs_statx+0xb8/0x2b0 fs/stat.c:202
 vfs_lstat include/linux/fs.h:3178 [inline]
 __do_sys_newlstat fs/stat.c:374 [inline]
 __se_sys_newlstat+0x46/0x250 fs/stat.c:368
 __x64_sys_newlstat+0x2d/0x40 fs/stat.c:368
 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: 8729 Comm: syz-executor.5 Not tainted 5.9.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

Crashes (3):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report
ci2-upstream-kcsan-gce	2020/09/03 14:17	upstream	fc3abb53250a	abf9ba4f	.config	log	report
ci2-upstream-kcsan-gce	2020/08/27 02:49	upstream	15bc20c6af4c	318430cb	.config	log	report
ci2-upstream-kcsan-gce	2020/08/08 21:45	upstream	449dc8c97089	01975a06	.config	log	report