[PATCH 5.15 011/139] vhost/vsock: dont check owner in vhost_vsock_stop() while releasing

Greg Kroah-Hartman
2022-02-28T17:51:52Z

From: Stefano Garzarella <sgarzare@redhat.com>

commit a58da53ffd70294ebea8ecd0eb45fd0d74add9f9 upstream.

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>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/vhost/vsock.c | 21 ++++++++++++++-------
1 file changed, 14 insertions(+), 7 deletions(-)

--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -633,16 +633,18 @@ err:
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];
@@ -757,7 +759,12 @@ static int vhost_vsock_dev_release(struc
* 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);

@@ -872,7 +879,7 @@ static long vhost_vsock_dev_ioctl(struct
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)))