KCSAN: data-race in do_exit / futex_wait_queue

KCSAN: data-race in do_exit / futex_wait_queue_me (2)
Status: auto-closed as invalid on 2020/11/02 08:53
Reported-by: syzbot+@syzkaller.appspotmail.com
First crash: 431d, last: 431d

similar bugs (3):
Kernel	Title	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in do_exit / futex_wait_queue_me (3)	3	332d	361d	0/22	auto-closed as invalid on 2021/02/08 21:09
upstream	KCSAN: data-race in do_exit / futex_wait_queue_me (4)	5	202d	258d	0/22	auto-closed as invalid on 2021/06/19 09:40
upstream	KCSAN: data-race in do_exit / futex_wait_queue_me	3	491d	521d	0/22	auto-closed as invalid on 2020/09/02 20:47

Sample crash report:

==================================================================
BUG: KCSAN: data-race in do_exit / futex_wait_queue_me

write to 0xffff8880a6e40064 of 4 bytes by task 24813 on cpu 1:
 freezer_count include/linux/freezer.h:121 [inline]
 freezable_schedule include/linux/freezer.h:173 [inline]
 futex_wait_queue_me+0x1a8/0x250 kernel/futex.c:2588
 futex_wait+0x145/0x390 kernel/futex.c:2690
 do_futex+0x145c/0x21c0 kernel/futex.c:3749
 __do_sys_futex kernel/futex.c:3810 [inline]
 __se_sys_futex+0x26d/0x330 kernel/futex.c:3778
 __x64_sys_futex+0x74/0x80 kernel/futex.c:3778
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880a6e40064 of 4 bytes by task 24765 on cpu 0:
 find_alive_thread kernel/exit.c:493 [inline]
 find_new_reaper kernel/exit.c:542 [inline]
 forget_original_parent kernel/exit.c:617 [inline]
 exit_notify kernel/exit.c:650 [inline]
 do_exit+0x7e0/0x16c0 kernel/exit.c:826
 do_group_exit+0xcb/0x180 kernel/exit.c:903
 get_signal+0xe9f/0x1650 kernel/signal.c:2757
 arch_do_signal+0x25/0x270 arch/x86/kernel/signal.c:811
 exit_to_user_mode_loop kernel/entry/common.c:161 [inline]
 exit_to_user_mode_prepare+0x124/0x210 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: 0 PID: 24765 Comm: syz-executor.3 Not tainted 5.9.0-rc7-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	2020/09/28 08:52	upstream	a1b8638ba132	6bfdbe89	.config	log	report			info