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Date: Sat, 30 May 2009 10:53:37 +0300 From: Pekka Enberg <penberg@...helsinki.fi> To: "Larry H." <research@...reption.com> CC: Alan Cox <alan@...rguk.ukuu.org.uk>, Ingo Molnar <mingo@...e.hu>, Rik van Riel <riel@...hat.com>, linux-kernel@...r.kernel.org, Linus Torvalds <torvalds@...l.org>, linux-mm@...ck.org, Ingo Molnar <mingo@...hat.com>, pageexec@...email.hu, Linus Torvalds <torvalds@...ux-foundation.org> Subject: Re: [patch 0/5] Support for sanitization flag in low-level page allocator Hi Larry, On 10:35 Sat 30 May, Pekka Enberg wrote: >> The GFP_SENSITIVE flag looks like a big hammer that we don't really >> need IMHO. It seems to me that most of the actual call-sites (crypto >> code, wireless keys, etc.) should probably just use kzfree() >> unconditionally to make sure we don't leak sensitive data. I did not >> look too closely but I don't think any of the sensitive kfree() calls >> are in fastpaths so the performance impact is negligible. Larry H. wrote: > That's hopeless, and kzfree is broken. Like I said in my earlier reply, > please test that yourself to see the results. Whoever wrote that ignored > how SLAB/SLUB work and if kzfree had been used somewhere in the kernel > before, it should have been noticed long time ago. An open-coded version of kzfree was being used in the kernel: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=00fcf2cb6f6bb421851c3ba062c0a36760ea6e53 Can we now get to the part where you explain how it's broken because I obviously "ignored how SLAB/SLUB works"? Thanks! Pekka -- 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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