Date: Tue, 22 Dec 2015 09:22:47 -0800 From: Dave Hansen <dave.hansen@...el.com> To: Christoph Lameter <cl@...ux.com> Cc: kernel-hardening@...ts.openwall.com, Pekka Enberg <penberg@...nel.org>, David Rientjes <rientjes@...gle.com>, Joonsoo Kim <iamjoonsoo.kim@....com>, Andrew Morton <akpm@...ux-foundation.org>, Laura Abbott <laura@...bott.name>, linux-mm@...ck.org, linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org> Subject: Re: [RFC][PATCH 6/7] mm: Add Kconfig option for slab sanitization On 12/22/2015 08:25 AM, Christoph Lameter wrote: > On Tue, 22 Dec 2015, Dave Hansen wrote: >> On 12/21/2015 07:40 PM, Laura Abbott wrote: >>> + The tradeoff is performance impact. The noticible impact can vary >>> + and you are advised to test this feature on your expected workload >>> + before deploying it >> >> What if instead of writing SLAB_MEMORY_SANITIZE_VALUE, we wrote 0's? >> That still destroys the information, but it has the positive effect of >> allowing a kzalloc() call to avoid zeroing the slab object. It might >> mitigate some of the performance impact. > > We already write zeros in many cases or the object is initialized in a > different. No one really wants an uninitialized object. The problem may be > that a freed object is having its old content until reused. Which is > something that poisoning deals with. Or are you just saying that we should use the poisoning *code* that we already have in slub? Using the _code_ looks like a really good idea, whether we're using it to write POISON_FREE, or 0's. Something like the attached patch? View attachment "slub-poison-zeros.patch" of type "text/x-patch" (1547 bytes)
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