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Date: Wed, 6 May 2026 15:56:22 +0200
From: Lukas Wunner <lukas@wunner.de>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>,
	"David S. Miller" <davem@davemloft.net>,
	Andrew Morton <akpm@linux-foundation.org>,
	Arnd Bergmann <arnd@arndb.de>,
	Andrey Ryabinin <ryabinin.a.a@gmail.com>,
	Ignat Korchagin <ignat@linux.win>,
	Stefan Berger <stefanb@linux.ibm.com>, linux-crypto@vger.kernel.org,
	linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
	Alexander Potapenko <glider@google.com>,
	Andrey Konovalov <andreyknvl@gmail.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Eric Biggers <ebiggers@kernel.org>,
	Nathan Chancellor <nathan@kernel.org>,
	David Laight <david.laight.linux@gmail.com>,
	"Jason A. Donenfeld" <Jason@zx2c4.com>,
	Ard Biesheuvel <ardb@kernel.org>
Subject: Re: [PATCH v2] crypto: ecc - Unbreak the build on arm with
 CONFIG_KASAN_STACK=y
Message-ID: <aftIhnaK7RKCO6F7@wunner.de>
References: <7e3d64a53efb28740b32d1f934e78c10086208ab.1778073318.git.lukas@wunner.de>
 <aftFQUoLcQTgW_CO@ashevche-desk.local>
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In-Reply-To: <aftFQUoLcQTgW_CO@ashevche-desk.local>

On Wed, May 06, 2026 at 04:42:25PM +0300, Andy Shevchenko wrote:
> On Wed, May 06, 2026 at 03:27:49PM +0200, Lukas Wunner wrote:
> > A longterm solution is to refactor ecc.c for reduced stack usage.  It
> > currently performs ECC point multiplication with a Montgomery ladder
> > which uses co-Z (conjugate) addition to trade off memory for speed.
> > The algorithm is susceptible to timing attacks and needs to be replaced
> > with a constant time Montgomery ladder, which should consume less memory
> > and thus resolve the stack usage issue as a side effect.
[...]
> > +# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124949
> 
> Perhaps also mention the algo change as that one sounds to me even more
> critical than this issue per se.

Hm, but it's already mentioned above in the commit message?