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@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>
---
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 (local)
---
 drivers/vhost/vsock.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

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