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    userns: Restrict when proc and sysfs can be mounted · 87a8ebd6
    Eric W. Biederman 提交于
    Only allow unprivileged mounts of proc and sysfs if they are already
    mounted when the user namespace is created.
    
    proc and sysfs are interesting because they have content that is
    per namespace, and so fresh mounts are needed when new namespaces
    are created while at the same time proc and sysfs have content that
    is shared between every instance.
    
    Respect the policy of who may see the shared content of proc and sysfs
    by only allowing new mounts if there was an existing mount at the time
    the user namespace was created.
    
    In practice there are only two interesting cases: proc and sysfs are
    mounted at their usual places, proc and sysfs are not mounted at all
    (some form of mount namespace jail).
    
    Cc: stable@vger.kernel.org
    Acked-by: NSerge Hallyn <serge.hallyn@canonical.com>
    Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>
    87a8ebd6
mount.c 4.6 KB