From: Lukas Wunner <lukas@wunner.de>
To: Anastasia Tishchenko <sv3iry@gmail.com>
Cc: Stefan Berger <stefanb@linux.ibm.com>,
Ignat Korchagin <ignat@linux.win>,
Herbert Xu <herbert@gondor.apana.org.au>,
"David S . Miller" <davem@davemloft.net>,
linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH v2] crypto: ecc - Fix carry overflow in vli multiplication
Date: Wed, 13 May 2026 16:31:55 +0200 [thread overview]
Message-ID: <agSLW1XpMab2VYNV@wunner.de> (raw)
In-Reply-To: <20260513105741.55534-1-sv3iry@gmail.com>
On Wed, May 13, 2026 at 01:57:40PM +0300, Anastasia Tishchenko wrote:
> The carry flag calculation fails when r01.m_high is saturated
> (0xFFFFFFFFFFFFFFFF) and addition of lower bits overflows.
>
> The condition (r01.m_high < product.m_high) doesn't handle the case
> where r01.m_high == product.m_high and an additional carry exists
> from lower-bit overflow.
>
> When commit 3c4b23901a0c ("crypto: ecdh - Add ECDH software support")
> introduced crypto/ecc.c, it split the muladd() function in the
> micro-ecc library into separate mul_64_64() and add_128_128() helpers.
> It seems the check got lost in translation.
>
> Add proper handling for this boundary by accounting for the carry
> from the lower addition.
>
> Fixes: 3c4b23901a0c ("crypto: ecdh - Add ECDH software support")
> Signed-off-by: Anastasia Tishchenko <sv3iry@gmail.com>
> Cc: stable@vger.kernel.org # v4.8+
Reviewed-by: Lukas Wunner <lukas@wunner.de>
prev parent reply other threads:[~2026-05-13 14:31 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-13 10:57 [PATCH v2] crypto: ecc - Fix carry overflow in vli multiplication Anastasia Tishchenko
2026-05-13 12:39 ` Qingfang Deng
2026-05-13 14:09 ` Lukas Wunner
2026-05-13 21:08 ` David Laight
2026-05-13 14:31 ` Lukas Wunner [this message]
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