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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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When the container does not have its own mount namespace,
prepareRootis run in the host mount namespace. Since commit 91ca331 (#1702, which made runc chroot into the container rootfs when there is no mount namespace), 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.
Related to #3118, #2095.