On Mon, Feb 21, 2022 at 12:49:16PM +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.
> Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko")
> Cc: stable@xxxxxxxxxxxxxxx
> Reported-by: syzbot+1e3ea63db39f2b4440e0@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
> ---
> drivers/vhost/vsock.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> index d6ca1c7ad513..f00d2dfd72b7 100644
> --- a/drivers/vhost/vsock.c
> +++ b/drivers/vhost/vsock.c
> @@ -629,16 +629,18 @@ static int vhost_vsock_start(struct vhost_vsock *vsock)
> return ret;
> }
>
> -static int vhost_vsock_stop(struct vhost_vsock *vsock)
> +static int vhost_vsock_stop(struct vhost_vsock *vsock, bool check_owner)
> {
> size_t i;
> int ret;
>
> mutex_lock(&vsock->dev.mutex);
>
> - ret = vhost_dev_check_owner(&vsock->dev);
> - if (ret)
> - goto err;
> + if (check_owner) {
> + ret = vhost_dev_check_owner(&vsock->dev);
> + if (ret)
> + goto err;
> + }
>
> for (i = 0; i < ARRAY_SIZE(vsock->vqs); i++) {
> struct vhost_virtqueue *vq = &vsock->vqs[i];
> @@ -753,7 +755,7 @@ static int vhost_vsock_dev_release(struct inode *inode, struct file *file)
> * inefficient. Room for improvement here. */
> vsock_for_each_connected_socket(vhost_vsock_reset_orphans);
>
> - vhost_vsock_stop(vsock);
Let's add an explanation:
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.
> + vhost_vsock_stop(vsock, false);
> vhost_vsock_flush(vsock);
> vhost_dev_stop(&vsock->dev);
>
> @@ -868,7 +870,7 @@ static long vhost_vsock_dev_ioctl(struct file *f, unsigned int ioctl,
> if (start)
> return vhost_vsock_start(vsock);
> else
> - return vhost_vsock_stop(vsock);
> + return vhost_vsock_stop(vsock, true);
> case VHOST_GET_FEATURES:
> features = VHOST_VSOCK_FEATURES;
> if (copy_to_user(argp, &features, sizeof(features)))
> --
> 2.35.1
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