KCSAN: data-race in lookup_fast / vfs

KCSAN: data-race in lookup_fast / vfs_rename
Status: auto-closed as invalid on 2020/09/04 03:18
Reported-by: syzbot+@syzkaller.appspotmail.com
First crash: 458d, last: 454d

similar bugs (1):
Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in lookup_fast / vfs_rename (2)				1	256d	256d	0/22	auto-closed as invalid on 2021/03/20 21:45

Sample crash report:

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

write to 0xffff88811d8d06c0 of 4 bytes by task 13509 on cpu 1:
 dont_mount include/linux/dcache.h:354 [inline]
 vfs_rename+0x970/0xba0 fs/namei.c:4313
 do_renameat2+0x554/0x930 fs/namei.c:4450
 __do_sys_rename fs/namei.c:4496 [inline]
 __se_sys_rename fs/namei.c:4494 [inline]
 __x64_sys_rename+0x3a/0x40 fs/namei.c:4494
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88811d8d06c0 of 4 bytes by task 5047 on cpu 0:
 d_revalidate fs/namei.c:767 [inline]
 lookup_fast+0x15f/0x370 fs/namei.c:1493
 open_last_lookups fs/namei.c:3135 [inline]
 path_openat+0x467/0x20e0 fs/namei.c:3357
 do_filp_open+0xbd/0x1d0 fs/namei.c:3387
 do_sys_openat2+0x33c/0x4a0 fs/open.c:1179
 do_sys_open fs/open.c:1195 [inline]
 ksys_open include/linux/syscalls.h:1388 [inline]
 __do_sys_open fs/open.c:1201 [inline]
 __se_sys_open fs/open.c:1199 [inline]
 __x64_sys_open+0xe2/0x110 fs/open.c:1199
 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: 5047 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 (2):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Title
ci2-upstream-kcsan-gce	2020/07/31 03:16	upstream	e2c46b5762c6	8df85ed9	.config	log	report
ci2-upstream-kcsan-gce	2020/07/27 06:31	upstream	92ed30191993	cb93dc6a	.config	log	report