KCSAN: data-race in __dentry_kill / d_alloc

KCSAN: data-race in __dentry_kill / d_alloc_parallel (2)
Status: auto-closed as invalid on 2020/09/05 03:58
Reported-by: syzbot+@syzkaller.appspotmail.com
First crash: 448d, last: 416d

similar bugs (3):
Kernel	Title	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in __dentry_kill / d_alloc_parallel	36	596d	699d	0/22	auto-closed as invalid on 2020/04/13 06:40
upstream	KCSAN: data-race in __dentry_kill / d_alloc_parallel (3)	1	380d	380d	0/22	auto-closed as invalid on 2020/10/11 15:50
upstream	KCSAN: data-race in __dentry_kill / d_alloc_parallel (4)	1	140d	140d	0/22	auto-closed as invalid on 2021/06/09 01:27

Sample crash report:

==================================================================
BUG: KCSAN: data-race in __dentry_kill / d_alloc_parallel

write to 0xffff88808ecc9540 of 4 bytes by task 28634 on cpu 1:
 d_alloc_parallel+0xb5b/0xd10 fs/dcache.c:2631
 __lookup_slow+0x7f/0x250 fs/namei.c:1529
 lookup_slow fs/namei.c:1561 [inline]
 walk_component+0x2a5/0x350 fs/namei.c:1860
 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:3302 [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+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88808ecc9540 of 4 bytes by task 29443 on cpu 0:
 dentry_unlist fs/dcache.c:544 [inline]
 __dentry_kill+0x1ef/0x450 fs/dcache.c:575
 dentry_kill fs/dcache.c:692 [inline]
 dput+0x208/0x420 fs/dcache.c:878
 handle_mounts fs/namei.c:1389 [inline]
 step_into+0x448/0xe70 fs/namei.c:1690
 walk_component+0x190/0x350 fs/namei.c:1866
 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:3302 [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+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 29443 Comm: systemd-udevd Not tainted 5.8.0-rc7-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	2020/08/01 03:54	upstream	7dc6fd0f3b84	8df85ed9	.config	log	report
ci2-upstream-kcsan-gce	2020/07/03 13:30	upstream	cdd3bb54332f	6e569755	.config	log	report
ci2-upstream-kcsan-gce	2020/06/30 23:45	upstream	7c30b859a947	c0383ebe	.config	log	report