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SubjectRe: [PATCH] Protection for exploiting null dereference using mmap
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On Tue, 2007-06-05 at 17:28 -0400, Eric Paris wrote:
> On Tue, 2007-06-05 at 17:16 -0400, Alan Cox wrote:
> > On Tue, Jun 05, 2007 at 05:00:51PM -0400, James Morris wrote:
> > > This should be an unsigned long.
> > >
> > > I wonder if the default should be for this value to be zero (i.e. preserve
> > > existing behavior). It could break binaries, albeit potentially insecure
> >
> > Agreed - DOSemu type apps and lrmi need to map at zero for vm86
>
> While I understand, there are a few users who will have problems with
> this default are we really better to not provide this defense in depth
> for the majority of users and let those with problems turn it off rather
> than provide no defense by default? I could even provide a different
> default for SELinux and non-SELinux if anyone saw value in that? But if
> others think that off default is best I'll send another patch shortly
> with the unsigned long fix and the default set to 0. My hope is then
> that distros will figure out to turn this on.

I'd be ok with having a different default for SELinux vs. non-SELinux,
i.e. no restrictions by default under dummy/capability, but restrict it
by default to 64k if selinux is enabled. Then we can use policy to
grant it as needed to the specific programs.

--
Stephen Smalley
National Security Agency

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