KCSAN: data-race in device_del / mm_update_next_owner

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 9c87c9f4 Merge tag 'arm-soc-fixes-v5.10-2' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=176a8841500000
kernel config: https://syzkaller.appspot.com/x/.config?x=e0bbcd06922dbd46
dashboard link: https://syzkaller.appspot.com/bug?extid=6838457992ef08cc6575
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [gre...@linuxfoundation.org linux-...@vger.kernel.org raf...@kernel.org]

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+683845...@syzkaller.appspotmail.com

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

write to 0xffff888009f46064 of 4 bytes by task 22491 on cpu 1:
memalloc_noio_save include/linux/sched/mm.h:197 [inline]
device_del+0x123/0x9a0 drivers/base/core.c:3087
device_unregister+0x11/0x30 drivers/base/core.c:3148
usb_remove_ep_devs+0x31/0x50 drivers/usb/core/endpoint.c:215
usb_disconnect+0x353/0x4b0 drivers/usb/core/hub.c:2236
hub_port_connect drivers/usb/core/hub.c:5073 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5362 [inline]
port_event drivers/usb/core/hub.c:5508 [inline]
hub_event+0x13bb/0x2b60 drivers/usb/core/hub.c:5590
process_one_work+0x3e1/0x950 kernel/workqueue.c:2272
process_scheduled_works kernel/workqueue.c:2334 [inline]
worker_thread+0x7ef/0xb90 kernel/workqueue.c:2420
kthread+0x1fa/0x220 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

read to 0xffff888009f46064 of 4 bytes by task 28626 on cpu 0:
mm_update_next_owner+0x1e9/0x4c0 kernel/exit.c:387
exit_mm+0x2ff/0x370 kernel/exit.c:485
do_exit+0x3c2/0x15a0 kernel/exit.c:796
do_group_exit+0x16f/0x170 kernel/exit.c:906
__do_sys_exit_group+0xb/0x10 kernel/exit.c:917
__se_sys_exit_group+0x5/0x10 kernel/exit.c:915
__x64_sys_exit_group+0x16/0x20 kernel/exit.c:915
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: 0 PID: 28626 Comm: syz-executor.4 Not tainted 5.10.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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[syzbot]

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