linux-kernel - Re: [PATCH v2] keys/encrypted: Fix two crypto-on-the-stack bugs

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Message-ID: <CALCETrX-YYp5iXPLKOpiT9+3DXYxGTVRXVyPN0oiYpQQC8kH3w@mail.gmail.com>
Date:   Tue, 13 Dec 2016 18:53:03 -0800
From:   Andy Lutomirski <luto@...capital.net>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        USB list <linux-usb@...r.kernel.org>,
        David Howells <dhowells@...hat.com>, keyrings@...r.kernel.org,
        Eric Biggers <ebiggers3@...il.com>,
        linux-crypto@...r.kernel.org,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Stephan Mueller <smueller@...onox.de>
Subject: Re: [PATCH v2] keys/encrypted: Fix two crypto-on-the-stack bugs

On Tue, Dec 13, 2016 at 6:48 PM, Andy Lutomirski <luto@...nel.org> wrote:
> The driver put a constant buffer of all zeros on the stack and
> pointed a scatterlist entry at it in two places.  This doesn't work
> with virtual stacks.  Use ZERO_PAGE instead.

Wait a second...

> -       sg_set_buf(&sg_out[1], pad, sizeof pad);
> +       sg_set_buf(&sg_out[1], empty_zero_page, 16);

My fix here is obviously bogus (I meant to use ZERO_PAGE(0)), but what
exactly is the code trying to do?  The old code makes no sense.  It's
setting the *output* buffer to zeroed padding.

--Andy