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@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)))