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    SubjectRe: [Bug #11500] /proc/net bug related to selinux
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    On Thu, 2008-09-18 at 14:34 -0400, Stephen Smalley wrote:
    > On Thu, 2008-09-18 at 11:09 -0700, Eric W. Biederman wrote:
    > > Stephen Smalley <sds@tycho.nsa.gov> writes:
    > >
    > > > On Thu, 2008-09-18 at 08:38 -0400, Stephen Smalley wrote:
    > > >> I do however think that the mantra that we can't require users to update
    > > >> policy for kernel changes is unsupportable in general. The precise set
    > > >> of permission checks on a given operation is not set in stone and it is
    > > >> not part of the kernel/userland interface/contract. Policy isn't
    > > >> "userspace"; it governs what userspace can do, and it has to adapt to
    > > >> kernel changes.
    > > >
    > > > I should note here that for changes to SELinux, we have gone out of our
    > > > way to avoid such breakage to date through the introduction of
    > > > compatibility switches, policy flags to enable any new checks, etc
    > > > (albeit at a cost in complexity and ever creeping compatibility code).
    > > > But changes to the rest of the kernel can just as easily alter the set
    > > > of permission checks that get applied on a given operation, and I don't
    > > > think we are always going to be able to guarantee that new kernel + old
    > > > policy will Just Work.
    > >
    > > I know of at least 2 more directories that I intend to turn into
    > > symlinks into somewhere under /proc/self. How do we keep from
    > > breaking selinux policies when I do that?
    >
    > I suspect we could tweak the logic in selinux_proc_get_sid() to always
    > label all symlinks under /proc with the base proc_t type already used
    > for e.g. /proc/self, at which point existing policies would be ok.

    FWIW, a fix for this issue has been applied to:
    git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/security-testing-2.6#next

    The particular commit can be viewed at:
    http://git.kernel.org/?p=linux/kernel/git/jmorris/security-testing-2.6.git;a=commit;h=ea6b184f7d521a503ecab71feca6e4057562252b

    This should address not only the /proc/net breakage but also any future
    changes to turn existing directories into symlinks.

    --
    Stephen Smalley
    National Security Agency



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