Re: [PATCH v4 2/3] mm/page_alloc.c: add config option to sanitize freed pages

[Pavel Machek <pavel@ucw.cz>]

On Mon 2015-05-18 14:41:19, Anisse Astier wrote:
> On Mon, May 18, 2015 at 1:21 PM, Pavel Machek <pavel@ucw.cz> wrote:
> > On Thu 2015-05-14 16:19:47, Anisse Astier wrote:
> >> This new config option will sanitize all freed pages. This is a pretty
> >> low-level change useful to track some cases of use-after-free, help
> >> kernel same-page merging in VM environments, and counter a few info
> >> leaks.
> >
> > Could you document the "few info leaks"? We may want to fix them for
> > !SANTIZE_FREED_PAGES case, too...
> >
> 
> I wish I could; I'd be sending patches for those info leaks, too.
> 
> What I meant is that this feature can also be used as a general
> protection mechanism against a certain class of info leaks; for
> example, some drivers allocating pages that were previously used by
> other subsystems, and then sending structures to userspace that
> contain padding or uninitialized fields, leaking kernel pointers.
> Having all pages cleared unconditionally can help a bit in some cases
> (hence "a few"), but it's of course not an end-all solution.

Ok. So there is class of errors where this helps, but you are not
aware of any such errors in kernel, so you can't fix them... Right?

> I'll edit the commit and kconfig messages to be more precise.

Thanks,
								Pavel
-- 
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