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    SubjectRe: CAP_SYS_ADMIN on restart(2)
    Quoting Oren Laadan (orenl@cs.columbia.edu):
    >
    >
    > Serge E. Hallyn wrote:
    > > Quoting Dave Hansen (dave@linux.vnet.ibm.com):
    > >> On Wed, 2009-04-15 at 23:21 +0400, Alexey Dobriyan wrote:
    > >>> Is sysctl to control CAP_SYS_ADMIN on restart(2) OK?
    > >> If the point is not to let users even *try* restarting things if it
    > >> *might* not work, then I guess this might be reasonable.
    > >>
    > >> If the goal is to increase security by always requiring CAP_SYS_ADMIN
    > >> for "dangerous" operations, I fear it will be harmful. We may have
    > >> people adding features that are not considering the security impact of
    > >> what they're doing just because the cases they care about all require
    > >> privilege.
    > >
    > > Nah, I disagree. (Or put another way, that wouldn't be the goal)
    > > There are two administrators we want to satisfy:
    > >
    > > 1. the one who wants his users to do partial checkpoints, but doesn't
    > > want to risk giving away any privilege at all in the process. He'll
    > > be satisified by setting restart(2) to not require cap_sys_admin,
    > > and his users just won't be able to do a whole container. A lot of
    > > users will be happy with that (though no SYSVIPC support, then).
    >
    > There is also a middle way: use setuid program to allow creation
    > of a new namespace (under your favorite policy), then drop the
    > privileges and continue as unprivileged inside that container.
    >
    > IOW, don't make the initial container-creation a barrier for the
    > entire operation.

    That is still possible here. But I don't think it's relevant.

    What Alexey wants, I believe, is for users to be able to not have
    to worry about there being exploitable bugs in restart(2) which
    unprivileged users can play with. And for the usual distro-kernel
    reasons, saying use 'CONFIG_CHECKPOINT=n' is not an option.

    -serge


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