KCSAN: data-race in __d_instantiate / lookup

KCSAN: data-race in __d_instantiate / lookup_fast (3)
Status: auto-closed as invalid on 2021/08/17 22:04
Reported-by: syzbot+@syzkaller.appspotmail.com
First crash: 97d, last: 97d

similar bugs (2):
Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in __d_instantiate / lookup_fast				6	541d	666d	0/22	auto-closed as invalid on 2020/06/18 13:33
upstream	KCSAN: data-race in __d_instantiate / lookup_fast (2)				1	250d	250d	0/22	auto-closed as invalid on 2021/03/18 02:49

Sample crash report:

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

write to 0xffff88812f624840 of 4 bytes by task 20996 on cpu 1:
 fsnotify_update_flags include/linux/fsnotify_backend.h:460 [inline]
 __d_instantiate+0x2c5/0x3c0 fs/dcache.c:1985
 d_instantiate_new+0x58/0x110 fs/dcache.c:2029
 ext4_mkdir+0x5fa/0x760 fs/ext4/namei.c:2955
 vfs_mkdir+0x2a4/0x370 fs/namei.c:3823
 do_mkdirat+0x11d/0x200 fs/namei.c:3848
 __do_sys_mkdir fs/namei.c:3866 [inline]
 __se_sys_mkdir fs/namei.c:3864 [inline]
 __x64_sys_mkdir+0x32/0x40 fs/namei.c:3864
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88812f624840 of 4 bytes by task 20977 on cpu 0:
 d_revalidate fs/namei.c:842 [inline]
 lookup_fast+0x15f/0x350 fs/namei.c:1595
 walk_component+0x5c/0x350 fs/namei.c:1955
 lookup_last fs/namei.c:2414 [inline]
 path_lookupat+0x12d/0x3d0 fs/namei.c:2438
 filename_lookup+0x118/0x3b0 fs/namei.c:2467
 user_path_at_empty+0x3b/0x50 fs/namei.c:2747
 user_path_at include/linux/namei.h:57 [inline]
 path_setxattr+0x4b/0x180 fs/xattr.c:590
 __do_sys_setxattr fs/xattr.c:611 [inline]
 __se_sys_setxattr fs/xattr.c:607 [inline]
 __x64_sys_setxattr+0x69/0x80 fs/xattr.c:607
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000000 -> 0x00280000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 20977 Comm: syz-executor.1 Not tainted 5.14.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

Crashes (1):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Title
ci2-upstream-kcsan-gce	2021/07/13 21:56	upstream	40226a3d96ef	70168d5c	.config	log	report			info	KCSAN: data-race in __d_instantiate / lookup_fast