linux-hardening - Re: [PATCH v2] gcc-plugins: latent

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Message-ID: <CAHmME9pV4SdoSyMq4kax3w3Vu1nPxjO3faCZKq8d0RDo8t731g@mail.gmail.com>
Date:   Tue, 5 Apr 2022 19:40:17 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, PaX Team <pageexec@...email.hu>
Subject: Re: [PATCH v2] gcc-plugins: latent_entropy: use /dev/urandom

Hi Kees,

On 4/5/22, Kees Cook <keescook@...omium.org> wrote:
> v3 uses a different check for the -f option, though? Isn't that
> preferred over the v2 method?

Based on the code comments, I assume this is gcc upstream's intended
method. It strikes me as worse, though, because that variable, when
it's not set to -1, is set to: `local_tick = (unsigned) tv.tv_sec *
1000 + tv.tv_usec / 1000;` which is on occasion unlucky and hits -1
too. But maybe that's a bug in gcc that should be fixed instead? I
don't know really. But anyway that's why I'm /also/ more into that
aspect of v2.

> Also, I did some quick benchmarking, and any difference in runtime is
> completely lost in the noise, so that's good.

Oh good to hear. So my 2k buffer is fine then.

Jason