linux-kernel - Re: [PATCH] random: discourage use of archrandom outside of rng

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Message-ID: <Yt5/hRD3V0eSzDWb@osiris>
Date:   Mon, 25 Jul 2022 13:33:25 +0200
From:   Heiko Carstens <hca@...ux.ibm.com>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     linux-kernel@...r.kernel.org, Borislav Petkov <bp@...e.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Rutland <mark.rutland@....com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Johannes Berg <johannes@...solutions.net>
Subject: Re: [PATCH] random: discourage use of archrandom outside of rng

On Mon, Jul 25, 2022 at 01:10:38PM +0200, Jason A. Donenfeld wrote:
> Borislav pointed out during the review of "random: handle archrandom
> with multiple longs" that people might actually use this function, which
> might not be good because the function has surprising semantics. This of
> course was also the case before that patch, and indeed RDSEED-like
> functions across architectures often behave surprisingly, failing often.
> While random.c has been written specifically to work with that behavior,
> not much else is well equipped for that.
> 
> So add a comment suggesting that this is not for general consumption.
> Fortunately, nobody uses this for general consumption anyway, and people
> who try quickly find themselves in trouble. But adding this comment out
> of an abundance of caution was nonetheless suggested, and it at least
> means there will be easier justification for cleaning up potential
> misuses of the function later.
> 
> Cc: Borislav Petkov <bp@...e.de>
> Cc: Heiko Carstens <hca@...ux.ibm.com>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Johannes Berg <johannes@...solutions.net>
> Suggested-by: Borislav Petkov <bp@...e.de>
> Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
> ---
>  arch/arm64/include/asm/archrandom.h   | 13 +++++++++++++
>  arch/powerpc/include/asm/archrandom.h |  8 ++++++++
>  arch/s390/include/asm/archrandom.h    |  8 ++++++++
>  arch/um/include/asm/archrandom.h      |  8 ++++++++
>  arch/x86/include/asm/archrandom.h     |  9 ++++++---
>  include/asm-generic/archrandom.h      |  8 ++++++++
>  6 files changed, 51 insertions(+), 3 deletions(-)

For s390:
Acked-by: Heiko Carstens <hca@...ux.ibm.com>