KCSAN: data-race in futex_wait_queue_me / task_dump

KCSAN: data-race in futex_wait_queue_me / task_dump_owner (2)
Status: moderation: reported on 2020/12/07 12:04
Reported-by: syzbot+f58565b98d68a7b60904@syzkaller.appspotmail.com
First crash: 59d, last: 27d

similar bugs (1):
Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in futex_wait_queue_me / task_dump_owner				63	104d	458d	0/17	auto-closed as invalid on 2020/11/16 10:32

Sample crash report:

kvm [10684]: vcpu0, guest rIP: 0x13c Hyper-V unhandled wrmsr: 0x40000024 data 0xb
==================================================================
BUG: KCSAN: data-race in futex_wait_queue_me / task_dump_owner

read-write to 0xffff888130d5102c of 4 bytes by task 10684 on cpu 0:
 freezer_count include/linux/freezer.h:121 [inline]
 freezable_schedule include/linux/freezer.h:173 [inline]
 futex_wait_queue_me+0x198/0x240 kernel/futex.c:2602
 futex_wait+0x145/0x3d0 kernel/futex.c:2704
 do_futex+0x105a/0x20c0 kernel/futex.c:3763
 __do_sys_futex kernel/futex.c:3826 [inline]
 __se_sys_futex+0x2a8/0x390 kernel/futex.c:3792
 __x64_sys_futex+0x74/0x80 kernel/futex.c:3792
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888130d5102c of 4 bytes by task 10689 on cpu 1:
 task_dump_owner+0x2b/0x1b0 fs/proc/base.c:1823
 pid_update_inode fs/proc/base.c:1965 [inline]
 pid_revalidate+0x69/0x110 fs/proc/base.c:1988
 lookup_fast+0x208/0x370 fs/namei.c:768
 walk_component+0x5c/0x350 fs/namei.c:1857
 link_path_walk+0x471/0x730 fs/namei.c:2182
 path_openat+0x19f/0x20a0 fs/namei.c:3367
 do_filp_open+0xbd/0x1d0 fs/namei.c:3398
 do_sys_openat2+0xa3/0x240 fs/open.c:1172
 do_sys_open fs/open.c:1188 [inline]
 __do_sys_open fs/open.c:1196 [inline]
 __se_sys_open fs/open.c:1192 [inline]
 __x64_sys_open+0xe2/0x110 fs/open.c:1192
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 10689 Comm: syz-executor.0 Not tainted 5.11.0-rc1-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	Maintainers
ci2-upstream-kcsan-gce	2020/12/29 03:19	upstream	c76e02c5	8259d56c	.config	log	report			info	dvhart@infradead.org, linux-kernel@vger.kernel.org, mingo@redhat.com, peterz@infradead.org, tglx@linutronix.de
ci2-upstream-kcsan-gce	2020/11/26 22:21	upstream	4df91062	2f1cec62	.config	log	report			info	dvhart@infradead.org, linux-kernel@vger.kernel.org, mingo@redhat.com, peterz@infradead.org, tglx@linutronix.de