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When the container does not have its own mount namespace, prepareRoot is run in the host mount namespace. Since commit 91ca331 ("chroot when no mount namespaces is provided"), this results in host's / being recursively made a slave (which, in the host mount namespace, means private), and the parent mount of the container rootfs being made private (or slave). In the host mount namespace, do not change the propagation of the existing mounts. Instead, make the new rootfs mount a slave, so that container mounts do not propagate to the host and other mount namespaces (otherwise, if the rootfs parent mount is shared, every container mount appears twice in the host mount namespace, and is propagated to all its slaves). Add an integration test. Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
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All the tests in this file need the same config modifications to run a container in the host mount namespace, so move those to setup. No functional change. Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
When the container does not have its own mount namespace, the container rootfs (bind mounted onto itself by runc) and all the container mounts (proc, dev etc.) are created in the host mount namespace, and are never unmounted, so they are left behind after the container is deleted. To fix, once the rootfs is mounted, remember its mount ID (and save it to the container state), and on container destroy, unmount it (together with all the container mounts under it), provided it is still the same mount. This way, a mount which was not created by runc is never unmounted. If rootfs is itself a shared mount, runc rootfs mount is propagated to its peers. If one of these peers is the mount rootfs is mounted on (e.g. rootfs is bind mounted onto itself on a shared mount), the copy gets tucked under the rootfs mount, and unmounting runc mount on destroy unmounts the rootfs mount, too. To prevent that, make rootfs a slave before creating runc rootfs mount. Add integration tests, and remove the workaround from host-mntns.bats teardown. This is a carry of PR opencontainers#3118 (with the implementation redone). Fixes opencontainers#2095. Co-authored-by: Steele Ray Desmond <steele@desmond.sh> Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
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Based on (and includes) #5537; please review the last two commits only.
When the container does not have its own mount namespace, the container rootfs (bind mounted onto itself by runc) and all the container mounts (proc, dev etc.) are created in the host mount namespace, and are never unmounted, so they are left behind after the container is deleted.
To fix, once the rootfs is mounted, remember its mount ID (and save it to the container state), and on container destroy, unmount it (together with all the container mounts under it), provided it is still the same mount. This way, a mount which was not created by runc is never unmounted.
If rootfs is itself a shared mount, runc rootfs mount is propagated to its peers. If one of these peers is the mount rootfs is mounted on (e.g. rootfs is bind mounted onto itself on a shared mount), the copy gets tucked under the rootfs mount, and unmounting runc mount on destroy unmounts the rootfs mount, too. To prevent that, make rootfs a slave before creating runc rootfs mount.
Add integration tests, and remove the workaround from
host-mntns.batsteardown.This is a carry of #3118 (with the implementation redone). Thanks to @SteeleDesmond for the original work.
Fixes #2095.
Closes #3118.