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Date: Fri, 24 Apr 2015 14:38:44 -0700 (PDT) From: David Rientjes <rientjes@...gle.com> To: Anisse Astier <anisse@...ier.eu> cc: Andrew Morton <akpm@...ux-foundation.org>, Mel Gorman <mgorman@...e.de>, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Alan Cox <gnomes@...rguk.ukuu.org.uk>, Linus Torvalds <torvalds@...ux-foundation.org>, Peter Zijlstra <peterz@...radead.org>, PaX Team <pageexec@...email.hu>, Brad Spengler <spender@...ecurity.net>, Kees Cook <keescook@...omium.org>, linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 2/2] mm/page_alloc.c: add config option to sanitize freed pages On Fri, 24 Apr 2015, Anisse Astier wrote: > diff --git a/mm/Kconfig b/mm/Kconfig > index 390214d..cb2df5f 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -635,3 +635,15 @@ config MAX_STACK_SIZE_MB > changed to a smaller value in which case that is used. > > A sane initial value is 80 MB. > + > +config SANITIZE_FREED_PAGES > + bool "Sanitize memory pages after free" > + default n > + help > + This option is used to make sure all pages freed are zeroed. This is > + quite low-level and doesn't handle your slab buffers. > + It has various applications, from preventing some info leaks to > + helping kernel same-page merging in virtualised environments. > + Depending on your workload, it will reduce performance of about 3%. > + > + If unsure, say N. Objection to allowing this without first enabling some other DEBUG config option, it should never be a standalone option, but also to pretending to have any insight into what the performance degredation of it will be. On my systems, this would be _massive_. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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