Re: [PATCH] vhost/vsock: don't check owner in vhost_vsock_stop() while releasing
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2022-02-21 15:03:58
Also in:
kvm, lkml, virtualization
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.
quoted hunk ↗ jump to hunk
Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") Cc: stable@vger.kernel.org Reported-by: syzbot+1e3ea63db39f2b4440e0@syzkaller.appspotmail.com Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> --- 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)
quoted hunk ↗ jump to hunk
{ 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.
quoted hunk ↗ jump to hunk
+ 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