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    SubjectRe: [PATCH v2] xattr: Enable security.capability in user namespaces
    Quoting Stefan Berger (stefanb@linux.vnet.ibm.com):
    > On 07/13/2017 08:38 PM, Eric W. Biederman wrote:
    > >Stefan Berger <stefanb@linux.vnet.ibm.com> writes:
    > >
    > >>On 07/13/2017 01:49 PM, Eric W. Biederman wrote:
    > >>
    > >>>My big question right now is can you implement Ted's suggested
    > >>>restriction. Only one security.foo or secuirty.foo@... attribute ?
    > >>We need to raw-list the xattrs and do the check before writing them. I am fairly sure this can be done.
    > >>
    > >>So now you want to allow security.foo and one security.foo@uid=<> or just a single one security.foo(@[[:print:]]*)?
    > >>
    > >The latter.
    >
    > That case would prevent a container user from overriding the xattr
    > on the host. Is that what we want? For limiting the number of xattrs

    Not really. If the file is owned by a uid mapped into the container,
    then the container root can chown the file which will clear the file
    capability, after which he can set a new one. If the file is not
    owned by a uid mapped into the container, then container root could
    not set a filecap anyway.

    -serge

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