Re: [PATCH 1/3] crypto: ecc - Fix carry overflow in vli multiplication

[Sascha Hauer <s.hauer@pengutronix.de>]

On Sun, 25 Oct 2026 09:54:44 +0100, Ahmad Fatoum wrote:
> This is an adoption of the corresponding Linux commit:
> 
> | commit 27b536a2ec8e2f85a0380c2d13c9ecbc7aaab406
> |
> |     crypto: ecc - Fix carry overflow in vli multiplication
> |
> |     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>
> |     Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
> 
> [...]

Applied, thanks!

[1/3] crypto: ecc - Fix carry overflow in vli multiplication
      https://git.pengutronix.de/cgit/barebox/commit/?id=ee1ddfaf4e91 (link may not be stable)
[2/3] crypto: ecc - Optimize vli additive operations using compiler builtins
      https://git.pengutronix.de/cgit/barebox/commit/?id=a6a5e2e775ea (link may not be stable)
[3/3] crypto: ecc - Handle exceptional points in Shamir multiplication
      https://git.pengutronix.de/cgit/barebox/commit/?id=7423e4755ecd (link may not be stable)

Best regards,
-- 
Sascha Hauer <s.hauer@pengutronix.de>