linux-hardening - Re: [PATCH v2 0/2] pstore: Replace crypto API compression with zlib calls

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Date:   Fri, 7 Jul 2023 17:55:27 -0300
From:   "Guilherme G. Piccoli" <gpiccoli@...lia.com>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Eric Biggers <ebiggers@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2 0/2] pstore: Replace crypto API compression with zlib
 calls

On 07/07/2023 05:34, Ard Biesheuvel wrote:
> The pstore layer implements support for compression of kernel log
> output, using a variety of compression algorithms provided by the
> [deprecated] crypto API 'comp' interface.
> 
> This appears to have been somebody's pet project rather than a solution
> to a real problem: the original deflate compression is reasonably fast,
> compresses well and is comparatively small in terms of code footprint,
> and so the flexibility that the crypto API integration provides does
> little more than complicate the code for no reason.
> 
> So let's get rid of this complexity, and switch back to zlib deflate
> using the library interface.
> 
> Changes since v1:
> - add missing vfree() of zlib compression workspace
> - implement improvements and simplifications suggested by Eric
> - add missing zlib_in/deflateEnd() calls
> - add code comment to document that the use of a library interface is
>   deliberate, and doesn't require a future 'upgrade' to the crypto API
> [...]

Thanks a lot Ard/Kees, quite a great improvement! I've tested on top of
6.4.0 in the Steam Deck and it's working perfectly fine - no noticeable
extra delay in the log collecting during panic compared to zstd.

Feel free to add (to the series):
Tested-by: Guilherme G. Piccoli <gpiccoli@...lia.com> # Steam Deck

Cheers,


Guilherme