Re: [Bug #11500] /proc/net bug related to selinux

david-gFPdbfVZQbY
2008-09-19T16:58:43Z

On Thu, 18 Sep 2008, Stephen Smalley wrote:

> On Thu, 2008-09-18 at 11:09 -0700, Eric W. Biederman wrote:
>> Stephen Smalley <sds-+05T5uksL2qpZYMLLGbcSA@public.gmane.org> 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.

so if proc is mounted anywhere other then /proc the selinux policy would
do odd things?

David Lang

>> For comparison how do we handle sysfs?
>
> Unresolved; presently has a single label for all nodes.
> See https://bugzilla.redhat.com/show_bug.cgi?id=228902
> for prior discussion of fine-grained labeling support for sysfs.
>
>> How do we handle device nodes in tmpfs?
>
> udev has selinux support - looks up the appropriate context in a
> userland config file (file_contexts) via libselinux matchpathcon(3) and
> sets it upon creation. tmpfs has long supported getting/setting
> security.* attributes.
>
>> Ultimately do we want to implement xattrs and inotify on /proc?
>> Or is there another way that would simplify maintenance?
>
> If proc supported setxattr, then I suppose early userspace could label
> it instead of the kernel needing to determine a label internally. But
> not sure how we'd cleanly migrate to avoid breakage with old userspace.
>
>