On Tue, Feb 22, 2022 at 5:47 PM Stefano Garzarella <sgarzare@xxxxxxxxxx> 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@xxxxxxxxxxxxxxx
> Reported-by: syzbot+1e3ea63db39f2b4440e0@xxxxxxxxxxxxxxxxxxxxxxxxx
> Reported-and-tested-by: syzbot+3140b17cb44a7b174008@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
> ---
> 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@xxxxxxxxxx
> ---
> drivers/vhost/vsock.c | 21 ++++++++++++++-------
> 1 file changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> index d6ca1c7ad513..37f0b4274113 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;
> + int ret = 0;
>
> 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 +755,12 @@ 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);
> + /* Don't check the owner, because we are in the release path, so we
> + * need to stop the vsock device in any case.
> + * vhost_vsock_stop() can not fail in this case, so we don't need to
> + * check the return code.
> + */
> + vhost_vsock_stop(vsock, false);
> vhost_vsock_flush(vsock);
> vhost_dev_stop(&vsock->dev);
>
> @@ -868,7 +875,7 @@ 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
>
