Messages in this thread | | | From | "PaX Team" <> | Date | Wed, 13 May 2015 11:50:20 +0200 | Subject | Re: [PATCH v3 2/4] PM / Hibernate: prepare for SANITIZE_FREED_PAGES |
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On 11 May 2015 at 9:59, Anisse Astier wrote:
> > Otherwise it looks good to me... if the sanitization is considered > > useful. Did it catch some bugs in the past? > > > > I've read somewhere that users of grsecurity claim that it caught bugs > in some drivers, but I haven't verified that personally; it's probably > much less useful than kasan (or even the original grsec feature) as a > bug-catcher since it doesn't clear freed slab buffers.
the PaX SANITIZE feature wasn't developed for catching use-after-free bugs but to help reduce data lifetime from the kernel while not killing too much performance (this is why i was reluctant to add a finer grained version to do slab object sanitization until Mathias Krause came up with a workable compromise).
another reason page zeroing isn't good at catching these bugs is that the 0 fill value will produce NULL pointers which are often explicitly handled already. on the other hand changing the fill value would not allow the __GFP_ZERO performance optimization (the slab sanitization feature is a different story however, we have a non-0 fill value and it keeps triggering use-after-free bugs).
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