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Miller" Cc: linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260508114844.29694-1-sv3iry@gmail.com> Content-Language: en-US From: Stefan Berger In-Reply-To: <20260508114844.29694-1-sv3iry@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-ORIG-GUID: x-JSgRWe9DDA-P8-pn_FEvAfXL9eYELI X-Proofpoint-GUID: FEgelG7xWC-hq_a6A92BmNwlhH2hBDDW X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTA4MDE1MCBTYWx0ZWRfX+Hvlnijp83Ba A8cQ7YYyrm/7AxwQ/Q9KINxA7IaQmdltHikhZWIthdGu5IlQ6vNOiIITv0tOmcmy++5NRgWtavG Whr1GRbJIaH2lUdVAwAsjdSDe0lnWNghuRiOaHXotqiiiZ6Rt5i1hC+DdxX/HSSCiFgMFJKw+2p aKmffYbGOJPNtG+5ZSYio6gCw0BD1XaDNEd4R8on6x0LeA0aq1k/9kn/hYyIBoPDj+3DIrICLzh qKGugt8gR8lnFl3vJ/PCziDfqyZu8qEbnbxSha0T3KXjgLesnv/ctuvFa+lsmzZHTk+Y5pSE8w8 QYmYqup0RjekN/BTexaLNocE0MlZjbQmZhCl2dyAU9aby0ACbhhBRkCH7EyxIw9vkuY3y/PCe+P guQfDzyphsyGeohzSLdTMUIJqvtTZkvsghqJUntPy4xPmjniDNHIYO8B0G6RsEJAib3DdD9K+IB tpLmH4iGsf9Fr4GCNbg== X-Authority-Analysis: v=2.4 cv=UbFhjqSN c=1 sm=1 tr=0 ts=69fdf4e4 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=pGLkceISAAAA:8 a=q09hNBxbWzpWlAAnaukA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-05-07_02,2026-05-08_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1011 spamscore=0 lowpriorityscore=0 malwarescore=0 suspectscore=0 adultscore=0 priorityscore=1501 bulkscore=0 phishscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604200000 definitions=main-2605080150 On 5/8/26 7:48 AM, 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. > > Add proper handling for this boundary by accounting for the carry > from the lower addition. > > This issue was discovered during formal verification of ECC functions. Thanks! > > Signed-off-by: Anastasia Tishchenko > --- > crypto/ecc.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/crypto/ecc.c b/crypto/ecc.c > index 43b0def3a225..dfe96471407c 100644 > --- a/crypto/ecc.c > +++ b/crypto/ecc.c > @@ -427,7 +427,10 @@ static void vli_mult(u64 *result, const u64 *left, const u64 *right, > product = mul_64_64(left[i], right[k - i]); > > r01 = add_128_128(r01, product); > - r2 += (r01.m_high < product.m_high); Maybe the following or something like lt_128(r01, product) would be 'better' replacing 'r01 < product': if (cmp_128(r01, product) < 0) r2++; /* Compare two uint128_t; returns -1 if a b.m_high) return 1; if (a.m_low < b.m_low) return -1; if (a.m_low > b.m_low) return 1; return 0; } /* r01 < product */ if (lt_128(r01, product)) r2++; /* Check a < b; return 1 if a < b, 0 otherwise */ static int lt_128(uint128_t a, uint128_t b) { if (a.m_high < b.m_high) return 1; if (a.m_high > b.m_high) return 0; if (a.m_low < b.m_low) return 1; return 0; } > + if (r01.m_high != product.m_high) > + r2 += (r01.m_high < product.m_high); > + else > + r2 += (r01.m_low < product.m_low); > } > > result[k] = r01.m_low; > @@ -488,7 +491,10 @@ static void vli_square(u64 *result, const u64 *left, unsigned int ndigits) > } > > r01 = add_128_128(r01, product); > - r2 += (r01.m_high < product.m_high); > + if (r01.m_high != product.m_high) > + r2 += (r01.m_high < product.m_high); > + else > + r2 += (r01.m_low < product.m_low); > } > > result[k] = r01.m_low;