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Date: Mon, 17 Oct 2022 12:29:03 -0700 From: Kees Cook <keescook@...omium.org> To: Ard Biesheuvel <ardb@...nel.org> Cc: "Guilherme G. Piccoli" <gpiccoli@...lia.com>, Anton Vorontsov <anton@...msg.org>, Colin Cross <ccross@...roid.com>, Tony Luck <tony.luck@...el.com>, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org Subject: Re: [PATCH] pstore: migrate to crypto acomp interface (take 2) On Mon, Oct 17, 2022 at 08:14:14PM +0200, Ard Biesheuvel wrote: > So once we use the same size for input and output, I was curious > whether we could encrypt in place, and get rid of the big_oops_buf. > And the answer is 'yes', precisely because we have this horrid per-CPU > allocation which serves as a bounce buffer. And this is not specific > to acomp, the old comp algorithms get wrapped in scomps which receive > the same treatment. Ah, in the sense that "in place" is actually happening in the per-cpu allocation, and only if it succeeds does the input buffer get overwritten? > So at that point, I wondered what the point is of all this complexity. > Do we really need 6 different algorithms to compress a couple of K of > ASCII text on a code path that is ice cold by definition? Wouldn't it > be better to drop the crypto API altogether here, and just use GZIP > via the library interface? Well, my goal was to make the algo "pstore doesn't care". If someone picks deflate, do they still get all the per-cpu allocations? -- Kees Cook
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