KCSAN: data-race in do_nanosleep / mm_update_next_owner (3)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 245a4300 Merge branch 'rcu/kcsan' into tip/locking/kcsan
git tree: https://github.com/google/ktsan.git kcsan
console output: https://syzkaller.appspot.com/x/log.txt?x=10cb599ee00000
kernel config: https://syzkaller.appspot.com/x/.config?x=a4b9db179318d21f
dashboard link: https://syzkaller.appspot.com/bug?extid=81dc40b3b7b55e9590bd
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
CC: [chri...@brauner.io ebie...@xmission.com linux-...@vger.kernel.org mi...@kernel.org ol...@redhat.com pet...@infradead.org tg...@linutronix.de el...@google.com]

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+81dc40...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in do_nanosleep / mm_update_next_owner

read to 0xffff88811ce6f064 of 4 bytes by task 10130 on cpu 1:
mm_update_next_owner+0x373/0x5a0 kernel/exit.c:389
exit_mm kernel/exit.c:484 [inline]
do_exit+0x4a4/0x18c0 kernel/exit.c:784
do_group_exit+0xb4/0x1c0 kernel/exit.c:895
__do_sys_exit_group kernel/exit.c:906 [inline]
__se_sys_exit_group kernel/exit.c:904 [inline]
__x64_sys_exit_group+0x2e/0x30 kernel/exit.c:904
do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff88811ce6f064 of 4 bytes by task 7998 on cpu 0:
freezer_count include/linux/freezer.h:121 [inline]
freezable_schedule include/linux/freezer.h:173 [inline]
do_nanosleep+0x14d/0x320 kernel/time/hrtimer.c:1874
hrtimer_nanosleep+0x191/0x320 kernel/time/hrtimer.c:1927
__do_sys_nanosleep kernel/time/hrtimer.c:1961 [inline]
__se_sys_nanosleep kernel/time/hrtimer.c:1948 [inline]
__x64_sys_nanosleep+0x106/0x150 kernel/time/hrtimer.c:1948
do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7998 Comm: syz-executor.4 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 7998 Comm: syz-executor.4 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x11d/0x181 lib/dump_stack.c:118
panic+0x210/0x640 kernel/panic.c:221
kcsan_report.cold+0xc/0xd kernel/kcsan/report.c:313
kcsan_setup_watchpoint+0x3fe/0x460 kernel/kcsan/core.c:416
check_access kernel/kcsan/core.c:459 [inline]
__tsan_unaligned_write4+0xc7/0x110 kernel/kcsan/core.c:588
freezer_count include/linux/freezer.h:121 [inline]
freezable_schedule include/linux/freezer.h:173 [inline]
do_nanosleep+0x14d/0x320 kernel/time/hrtimer.c:1874
hrtimer_nanosleep+0x191/0x320 kernel/time/hrtimer.c:1927
__do_sys_nanosleep kernel/time/hrtimer.c:1961 [inline]
__se_sys_nanosleep kernel/time/hrtimer.c:1948 [inline]
__x64_sys_nanosleep+0x106/0x150 kernel/time/hrtimer.c:1948
do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x4594a0
Code: c0 5b 5d c3 66 0f 1f 44 00 00 8b 04 24 48 83 c4 18 5b 5d c3 66 0f 1f 44 00 00 83 3d 91 f4 61 00 00 75 14 b8 23 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 d4 d1 fb ff c3 48 83 ec 08 e8 ea 46 00 00
RSP: 002b:00007ffccbc74fe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000023
RAX: ffffffffffffffda RBX: 0000000000022482 RCX: 00000000004594a0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007ffccbc74ff0
RBP: 00000000000000e2 R08: 0000000000000001 R09: 0000000000d69940
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000005
R13: 00007ffccbc75040 R14: 0000000000022401 R15: 00007ffccbc75050
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.