On Sat, 2007-11-17 at 08:58 +1100, James Morris wrote:
> On Fri, 16 Nov 2007, Eric Paris wrote:
>
> > On Sat, 2007-11-17 at 08:47 +1100, James Morris wrote:
> > > On Fri, 16 Nov 2007, Eric Paris wrote:
> > >
> > > > On a kernel with CONFIG_SECURITY but without an LSM which implements
> > > > security_file_mmap it is impossible for an application to mmap addresses
> > > > lower than mmap_min_addr.
> > >
> > > Actually, should we be doing any checking in the dummy module, given that
> > > it is not done with !CONFIG_SECURITY ?
> >
> > I'm not sure I understand the question. We already do a number of
> > capable type security checks in dummy functions. See dummy_settime() as
> > just one example.
>
> I mean just in this case. If no mmap_min_addr check is done without
> CONFIG_SECURITY, then perhaps none should be done in the dummy module,
> i.e. preserving existing behavior. LSM is theoretically supposed to be
> unnoticable from a behavioral pov unless a non-dummy module is loaded.
When this protection was originally concieved it intentionally was
offing something even without an more 'full featured' LSM. That was the
whole reason I had to drop the secondary stacking hook inside the
selinux code.
While I now understand the question, I think that this is the behavior
most people would want. I'll revert the security enhancement for
non-LSM systems if others agree with James, but I think adding another
small bit of protection against kernel flaws for everyone who wants
security is a win. (and remember, in kernel we still default this to
off so noone is going to 'accidentally' see and security checks in the
dummy hooks)
-Eric
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