87c0724076
libdm currently has a fairly substantial DoS bug that makes certain operations fail on a libdm device if the device has active references through mountpoints. This is a significant problem with the advent of mount namespaces and MS_PRIVATE, and can cause certain --volume mounts to cause libdm to no longer be able to remove containers: % docker run -d --name testA busybox top % docker run -d --name testB -v /var/lib/docker:/docker busybox top % docker rm -f testA [fails on libdm with dm_task_run errors.] This also solves the problem of unprivileged users being able to DoS docker by using unprivileged mount namespaces to preseve mounts that Docker has dropped. Signed-off-by: Aleksa Sarai <asarai@suse.de> Upstream-commit: 92e45b81e0a8b68d9567a2068247460a1ba59600 Component: engine