On Tue, Feb 22, 2022 at 5:47 PM Stefano Garzarella sgarzare@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.

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@vger.kernel.org Reported-by: syzbot+1e3ea63db39f2b4440e0@syzkaller.appspotmail.com Reported-and-tested-by: syzbot+3140b17cb44a7b174008@syzkaller.appspotmail.com Signed-off-by: Stefano Garzarella sgarzare@redhat.com

Acked-by: Jason Wang jasowang@redhat.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@redh...

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