KCSAN: data-race in dput / vfs

KCSAN: data-race in dput / vfs_rename (4)
Status: auto-closed as invalid on 2020/11/13 11:07
Reported-by: syzbot+@syzkaller.appspotmail.com
First crash: 294d, last: 294d

similar bugs (4):
Kernel	Title	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in dput / vfs_rename (3)	2	385d	405d	0/22	auto-closed as invalid on 2020/08/14 12:58
upstream	KCSAN: data-race in dput / vfs_rename (5)	5	142d	201d	0/22	auto-closed as invalid on 2021/04/14 19:39
upstream	KCSAN: data-race in dput / vfs_rename (2)	1	499d	499d	0/22	auto-closed as invalid on 2020/05/27 13:23
upstream	KCSAN: data-race in dput / vfs_rename	1	607d	607d	0/22	auto-closed as invalid on 2020/02/09 03:47

Sample crash report:

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

write to 0xffff8881205d1240 of 4 bytes by task 5760 on cpu 0:
 dont_mount include/linux/dcache.h:354 [inline]
 vfs_rename+0x9a3/0xe30 fs/namei.c:4319
 do_renameat2+0x554/0x940 fs/namei.c:4456
 __do_sys_rename fs/namei.c:4502 [inline]
 __se_sys_rename fs/namei.c:4500 [inline]
 __x64_sys_rename+0x3a/0x40 fs/namei.c:4500
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881205d1240 of 4 bytes by task 5081 on cpu 1:
 fast_dput fs/dcache.c:746 [inline]
 dput+0x2f/0x420 fs/dcache.c:865
 __fput+0x398/0x4d0 fs/file_table.c:294
 ____fput+0x11/0x20 fs/file_table.c:314
 task_work_run+0x8e/0x110 kernel/task_work.c:141
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:165 [inline]
 exit_to_user_mode_prepare+0x1b2/0x210 kernel/entry/common.c:192
 syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:267
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 5081 Comm: systemd-udevd Not tainted 5.9.0-rc8-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	2020/10/09 11:01	upstream	583090b1b823	fa79ed2a	.config	log	report			info