KCSAN: data-race in drop_nlink / vfs_getattr

KCSAN: data-race in drop_nlink / vfs_getattr_nosec (3)
Status: auto-closed as invalid on 2021/09/07 16:42
Reported-by: syzbot+@syzkaller.appspotmail.com
First crash: 95d, last: 77d

similar bugs (2):
Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in drop_nlink / vfs_getattr_nosec				1	216d	216d	0/22	auto-closed as invalid on 2021/04/21 10:41
upstream	KCSAN: data-race in drop_nlink / vfs_getattr_nosec (2)				6	143d	176d	0/22	auto-closed as invalid on 2021/07/03 10:04

Sample crash report:

==================================================================
BUG: KCSAN: data-race in drop_nlink / vfs_getattr_nosec

write to 0xffff8881079edb38 of 4 bytes by task 21156 on cpu 0:
 drop_nlink+0x37/0x90 fs/inode.c:305
 shmem_unlink+0x1ab/0x1d0 mm/shmem.c:2935
 shmem_rename2+0x2fd/0x440 mm/shmem.c:3031
 vfs_rename+0xa03/0xfb0 fs/namei.c:4551
 do_renameat2+0x59e/0x9b0 fs/namei.c:4706
 __do_sys_rename fs/namei.c:4755 [inline]
 __se_sys_rename fs/namei.c:4753 [inline]
 __x64_sys_rename+0x58/0x60 fs/namei.c:4753
 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 0xffff8881079edb38 of 4 bytes by task 21167 on cpu 1:
 generic_fillattr fs/stat.c:49 [inline]
 vfs_getattr_nosec+0x1c1/0x2f0 fs/stat.c:108
 vfs_getattr fs/stat.c:142 [inline]
 vfs_statx+0x128/0x290 fs/stat.c:207
 vfs_fstatat fs/stat.c:225 [inline]
 vfs_lstat include/linux/fs.h:3386 [inline]
 __do_sys_newlstat fs/stat.c:380 [inline]
 __se_sys_newlstat+0x46/0x250 fs/stat.c:374
 __x64_sys_newlstat+0x2d/0x40 fs/stat.c:374
 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: 0x00000001 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 21167 Comm: systemd-udevd Not tainted 5.14.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

Crashes (2):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Title
ci2-upstream-kcsan-gce	2021/08/03 16:36	upstream	c500bee1c5b2	6c236867	.config	log	report			info	KCSAN: data-race in drop_nlink / vfs_getattr_nosec
ci2-upstream-kcsan-gce	2021/07/16 11:10	upstream	d936eb238744	f115ae98	.config	log	report			info	KCSAN: data-race in drop_nlink / vfs_getattr_nosec