linux-kernel - Re: [PATCH v2 3/7] vhost: Add kthread support in function vhost_workers

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Message-ID: <lpwqg4j2nnh3xgg64vrlk635vcmu2bxrq37sapwp3yl2pdp5rz@lg3wgfop6rkx>
Date: Tue, 15 Oct 2024 08:52:28 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Cindy Lu <lulu@...hat.com>
Cc: Mike Christie <michael.christie@...cle.com>, jasowang@...hat.com, 
	mst@...hat.com, linux-kernel@...r.kernel.org, 
	virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v2 3/7] vhost: Add kthread support in function
 vhost_workers_free()

On Tue, Oct 15, 2024 at 02:05:47PM +0800, Cindy Lu wrote:
>On Tue, 15 Oct 2024 at 05:06, Mike Christie <michael.christie@...cle.com> wrote:
>>
>> On 10/3/24 8:58 PM, Cindy Lu wrote:
>> > +static void vhost_workers_free(struct vhost_dev *dev)
>> > +{
>> > +     if (enforce_inherit_owner)
>> > +             vhost_workers_free_task(dev);
>> > +     else
>> > +             vhost_workers_free_kthread(dev);
>> > +}
>>
>> With patch 7, userspace could change enforce_inherit_owner after
>> we created thread and we would call the wrong function above.
>>
>enforce_inherit_owner will only change before the owner was set.

As I pointed out in patch 7, enforce_inherit_owner seems to be shared 
among all vhost devices, so what happens if for example a user sets it 
to /dev/vhost-net, while /dev/vhost-vsock is already initialized and 
therefore already has an owner?

Thanks,
Stefano

>the process is like set enforce_inherit_owner---->set owner->
>thread/task creating
>in in patch 7's code I have add the check for vhost's owner, if the
>owner was set, the ioctl
>to set enforce_inherit_owner will fail
>Thanks
>Cindy
>
>