linux-kernel - Re: [PATCH v8 0/9] crypto: Remove VLA usage

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Date:   Mon, 3 Sep 2018 22:50:41 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     Eric Biggers <ebiggers@...gle.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Giovanni Cabiddu <giovanni.cabiddu@...el.com>,
        Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>,
        Tudor-Dan Ambarus <tudor.ambarus@...rochip.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Arnd Bergmann <arnd@...db.de>,
        Will Deacon <will.deacon@....com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Matthew Wilcox <willy@...radead.org>,
        "David S. Miller" <davem@...emloft.net>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        linux-crypto <linux-crypto@...r.kernel.org>,
        device-mapper development <dm-devel@...hat.com>,
        qat-linux@...el.com, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8 0/9] crypto: Remove VLA usage

On Mon, Sep 3, 2018 at 10:19 PM, Herbert Xu <herbert@...dor.apana.org.au> wrote:
> On Tue, Aug 07, 2018 at 02:18:34PM -0700, Kees Cook wrote:
>> v8 cover letter:
>>
>> I continue to hope this can land in v4.19, but I realize that's unlikely.
>> It would be nice, though, if some of the "trivial" patches could get taken
>> (e.g. cbc, xcbc, ccm VLA removals) so I don't have to keep repeating them.
>> *fingers crossed*
>>
>> Series cover letter:
>>
>> This is nearly the last of the VLA removals[1], but it's one of the
>> largest because crypto gets used in lots of places. After looking
>> through code, usage, reading the threads Gustavo started, and comparing
>> the use-cases to the other VLA removals that have landed in the kernel,
>> I think this series is likely the best way forward to shut the door on
>> VLAs forever.
>>
>> For background, the crypto stack usage is for callers to do an immediate
>> bit of work that doesn't allocate new memory. This means that other VLA
>> removal techniques (like just using kmalloc) aren't workable, and the
>> next common technique is needed: examination of maximum stack usage and
>> the addition of sanity checks. This series does that, and in several
>> cases, these maximums were already implicit in the code.
>>
>> This series is intended to land via the crypto tree for 4.19, though it
>> touches dm, networking, and a few other things as well, since there are
>> dependent patches (new crypto #defines being used, etc).
>
> I have applied patches 1-4 and 6-8.  I'd like to get an ack from
> the dm folks regarding patch 5.  As to patch 9, please fix it so
> it doesn't rely on the BUG_ON to catch things.

Great! Thanks very much. I'll get a patch prepared to plumb
crypto_skcipher_set_reqsize() failures.

-Kees

-- 
Kees Cook
Pixel Security