linux-kernel - Re: [PATCH] crypto: testmgr - reduce stack usage in fuzzers

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Message-ID: <CAK8P3a0G2K4u-Sh495O7_nfc6zydtZBTOJcq19g3YYQA2ZMKFA@mail.gmail.com>
Date:   Mon, 17 Jun 2019 16:54:16 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     Kees Cook <keescook@...omium.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Biggers <ebiggers@...gle.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Vitaly Chikunov <vt@...linux.org>,
        Gilad Ben-Yossef <gilad@...yossef.com>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] crypto: testmgr - reduce stack usage in fuzzers

On Mon, Jun 17, 2019 at 4:24 PM Herbert Xu <herbert@...dor.apana.org.au> wrote:
>
> On Mon, Jun 17, 2019 at 04:10:44PM +0200, Arnd Bergmann wrote:
> >
> > In most cases, this ends up in favor of clang (concerning the stack
> > warning size limit) because most variables are small, but here we have
> > a large stack object (two objects for the hash fuzzing) with a large redzone.
>
> Oh I missed the fact that there is another large stack variable
> further up the stack.  So what happens if you just convert that
> one and leave the shash descriptor alone?

Just converting the three testvec_config variables is what I originally
had in my patch. It got some configurations below the warning level,
but some others still had the problem. I considered sending two
separate patches, but as the symptom was the same, I just folded
it all into one patch that does the same thing in four functions.

       Arnd