linux-kernel - Re: Crypto Fixes for 4.12

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Message-Id: <20170615.110118.912361155799259361.davem@davemloft.net>
Date:   Thu, 15 Jun 2017 11:01:18 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     torvalds@...ux-foundation.org
Cc:     herbert@...dor.apana.org.au, linux-kernel@...r.kernel.org,
        linux-crypto@...r.kernel.org
Subject: Re: Crypto Fixes for 4.12

From: Linus Torvalds <torvalds@...ux-foundation.org>
Date: Thu, 15 Jun 2017 18:04:44 +0900

> There's a fair number of SHASH_DESC_ON_STACK users, are all the others
> safe for some random reason that just happens to be about code
> generation? Did people actually verify that?

I looked at the code generated in every case.

As a side note, ext4 does something similar with a private
implementation, but it doesn't use something the evaluates to an
alloca.  Instead it uses a fixed 4-byte size for the shash context
value in the on-stack declaration.

We can tidy it up with abstraction macros as a follow-up, thanks
for the suggestion.  I'll look into it.