[syzbot] KASAN: use-after-free Write in expire_timers

[syzbot]

> On 2022/11/22 2:35, syzbot wrote:
>> Hello,
>> 
>> syzbot found the following issue on:
>> 
>> HEAD commit:    b6e7fdfd6f6a Merge tag 'iommu-fixes-v6.1-rc5' of git://git..
>> git tree:       upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=11c28f95880000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=95fb379f123ba8ce
>> dashboard link: https://syzkaller.appspot.com/bug?extid=38ee3533e07da8749f85
>> compiler:       aarch64-linux-gnu-gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
>> userspace arch: arm64
>
> Fix data race between virtual_ncidev_close() and virtual_ncidev_open().
>
> #syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

This crash does not have a reproducer. I cannot test it.

> b6e7fdfd6f6a
>
> --- a/drivers/nfc/virtual_ncidev.c
> +++ b/drivers/nfc/virtual_ncidev.c
> @@ -161,12 +161,8 @@ static int virtual_ncidev_close(struct inode *inode,
> struct file *file)
>
>     if (state == virtual_ncidev_enabled) {
>         state = virtual_ncidev_disabling;
> -       mutex_unlock(&nci_mutex);
> -
>         nci_unregister_device(ndev);
>         nci_free_device(ndev);
> -
> -       mutex_lock(&nci_mutex);
>     }
>
>     state = virtual_ncidev_disabled;
> --