linux-hardening - Re: [PATCH] pstore: migrate to crypto acomp interface (take 2)

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Message-ID: <202210171307.32A5D9C07@keescook>
Date:   Mon, 17 Oct 2022 13:11:23 -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 09:45:08PM +0200, Ard Biesheuvel wrote:
> On Mon, 17 Oct 2022 at 21:40, Kees Cook <keescook@...omium.org> wrote:
> > Okay, so strictly speaking, eliminating the per-CPU allocation is an
> > improvement. Keeping scomp and doing in-place compression will let
> > pstore use "any" compressions method.
> 
> I'm not following the point you are making here.

Sorry, I mean to say that if I leave scomp in pstore, nothing is "worse"
(i.e. the per-cpu allocation is present in both scomp and acomp). i.e.
no regression either way, but if we switch to a distinct library call,
it's an improvement on the memory utilization front.

> > Is there a crypto API that does _not_ preallocate the per-CPU stuff?
> > Because, as you say, it's a huge amount of memory on the bigger
> > systems...
> 
> The library interface for each of the respective algorithms.

Where is the crypto API for just using the library interfaces, so I
don't have to be tied to a specific algo?

-- 
Kees Cook