Virtualization - Feb 2022 - [PATCH] vhost/vsock: don't check owner in vhost_vsock_stop() while releasing

On Mon, Feb 21, 2022 at 09:44:39PM +0530, Anirudh Rayabharam
wrote:
>On Mon, Feb 21, 2022 at 02:59:30PM +0100, Stefano Garzarella wrote:
>> On Mon, Feb 21, 2022 at 12:49 PM Stefano Garzarella <sgarzare at
redhat.com> wrote:
>> >
>> > vhost_vsock_stop() calls vhost_dev_check_owner() to check the
device
>> > ownership. It expects current->mm to be valid.
>> >
>> > vhost_vsock_stop() is also called by vhost_vsock_dev_release()
when
>> > the user has not done close(), so when we are in do_exit(). In
this
>> > case current->mm is invalid and we're releasing the device,
so we
>> > should clean it anyway.
>> >
>> > Let's check the owner only when vhost_vsock_stop() is called
>> > by an ioctl.
>> >
>> > Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko")
>> > Cc: stable at vger.kernel.org
>> > Reported-by: syzbot+1e3ea63db39f2b4440e0 at
syzkaller.appspotmail.com
>> > Signed-off-by: Stefano Garzarella <sgarzare at redhat.com>
>> > ---
>> >  drivers/vhost/vsock.c | 14 ++++++++------
>> >  1 file changed, 8 insertions(+), 6 deletions(-)
>>
>> Reported-and-tested-by: syzbot+0abd373e2e50d704db87 at
syzkaller.appspotmail.com
>
>I don't think this patch fixes "INFO: task hung in
vhost_work_dev_flush"
>even though syzbot says so. I am able to reproduce the issue locally
>even with this patch applied.
Are you using the sysbot reproducer or another test?
In that case, can you share it?

 From the stack trace it seemed to me that the worker accesses a zone 
that has been cleaned (iotlb), so it is invalid and fails.
That's why I had this patch tested which should stop the worker before 
cleaning.

Thanks,
Stefano