linux-kernel - Re: [PATCH v2] vhost/vsock: don't check owner in vhost_vsock

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Date:   Thu, 24 Feb 2022 08:53:31 +0000
From:   Stefan Hajnoczi <stefanha@...hat.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>, netdev@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        syzbot+1e3ea63db39f2b4440e0@...kaller.appspotmail.com,
        kvm@...r.kernel.org, Anirudh Rayabharam <mail@...rudhrb.com>,
        syzbot+3140b17cb44a7b174008@...kaller.appspotmail.com,
        linux-kernel@...r.kernel.org,
        Mike Christie <michael.christie@...cle.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        stable@...r.kernel.org
Subject: Re: [PATCH v2] vhost/vsock: don't check owner in vhost_vsock_stop()
 while releasing

On Tue, Feb 22, 2022 at 10:47:42AM +0100, Stefano Garzarella 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.
> 
> When invoked from release we can not fail so we don't check return
> code of vhost_vsock_stop(). We need to stop vsock even if it's not
> the owner.
> 
> Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko")
> Cc: stable@...r.kernel.org
> Reported-by: syzbot+1e3ea63db39f2b4440e0@...kaller.appspotmail.com
> Reported-and-tested-by: syzbot+3140b17cb44a7b174008@...kaller.appspotmail.com
> Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
> ---
> v2:
> - initialized `ret` in vhost_vsock_stop [Dan]
> - added comment about vhost_vsock_stop() calling in the code and an explanation
>   in the commit message [MST]
> 
> v1: https://lore.kernel.org/virtualization/20220221114916.107045-1-sgarzare@redhat.com
> ---
>  drivers/vhost/vsock.c | 21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)

Reviewed-by: Stefan Hajnoczi <stefanha@...hat.com>

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