From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DB01E56C65F; Wed, 9 Sep 2026 14:36:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788964596; cv=none; b=r8bKsCOVNyysNWnwKfuI/sN0IiH/J9bmghN1FmkwTyYcwE5EL5e/aJ9Dc44XEgjQxJN08Yl7X9a/iDp1NGBRp6sAajnIUCW/KW9sNE7nN3Ckqgb6jNV98w27hi3UdXXQhVLs9DxfEohnhfxGD1wWSHOFpffR9aWGZbUY19Iob8k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788964596; c=relaxed/simple; bh=I9G6YcGFW0rwbNOGyyILKpekXSuTl8cA+ylB8HTRmp8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ovzueY+hoh3gjIyBovRRvGTDvzxyX7bwTSI2KU6tpZdI5PQ514VWEKL/Hn6aBIFNkhBGf6kZ4HJQfC+xanAsqUOE1qauOinsw+brpxcNFfXoVxZBdxjGELFNb+HP9sbXUAbRvn7h+ntU9WRwXVbI8llL2NaAzeQi7Y9T2+fnn/0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=O2hcnj+A; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="O2hcnj+A" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 16D791F00A3A; Wed, 9 Sep 2026 14:36:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788964594; bh=eq9Od4w5QB8vCCYwxkbxoqmV1xv6NqPdGn6/OJMm7AQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=O2hcnj+AFyWenFgIs/vUn7mr3I8r03rc4XDc2ktaRxtpL3a/sOlRgduUl8E4YjXWa xhLiJpt1dl3e381OTPET7tZYd3OcYCcXDYMU2SdPvrery4uah9sm/6qCHgxiwnbnZ3 HsUS4NgeHuDYw+FcJTJavRHfCEqeUlTIpkJQX2kI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Thorsten Blum , Herbert Xu , Sasha Levin Subject: [PATCH 6.18 440/583] crypto: atmel-ecc - clean up and improve ECDH comments Date: Wed, 9 Sep 2026 15:42:05 +0200 Message-ID: <20260909134253.229788227@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260909134237.773280130@linuxfoundation.org> References: <20260909134237.773280130@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Thorsten Blum [ Upstream commit 3e84fb698abada239d3e35ed3d52a24dbfda5f6a ] Improve the kerneldoc for struct atmel_ecdh_ctx by removing the stale "unsupported curves" wording, since the device only supports a single curve (P-256), and move the set_secret() constraint to the description. In atmel_ecdh_set_secret(), clarify that the device generates the private key, and drop the redundant "only supports NIST P256" comment. In atmel_ecdh_done() and atmel_ecdh_generate_public_key(), clarify the truncation comments. Also note that a P-256 public key consists of two 32-byte coordinates in atmel_ecdh_compute_shared_secret(), and remove the unnecessary fall-through comment and other redundant comments. Signed-off-by: Thorsten Blum Signed-off-by: Herbert Xu Stable-dep-of: f07a0d251db7 ("crypto: atmel-ecc - avoid stale fallback key after set_secret failure") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/crypto/atmel-ecc.c | 38 ++++++++++++++------------------------ 1 file changed, 14 insertions(+), 24 deletions(-) --- a/drivers/crypto/atmel-ecc.c +++ b/drivers/crypto/atmel-ecc.c @@ -27,15 +27,14 @@ static struct atmel_ecc_driver_data driv /** * struct atmel_ecdh_ctx - transformation context - * @client : pointer to i2c client device - * @fallback : used for unsupported curves or when user wants to use its own - * private key. - * @public_key : generated when calling set_secret(). It's the responsibility - * of the user to not call set_secret() while - * generate_public_key() or compute_shared_secret() are in flight. - * @curve_id : elliptic curve id - * @do_fallback: true when the device doesn't support the curve or when the user - * wants to use its own private key. + * @client: I2C client device + * @fallback: ECDH fallback used for caller-provided private keys + * @public_key: cached public key for the device-generated private key + * @curve_id: elliptic curve id + * @do_fallback: true when ECDH operations should use @fallback + * + * The caller must not invoke set_secret() while generate_public_key() + * or compute_shared_secret() are in flight. */ struct atmel_ecdh_ctx { struct i2c_client *client; @@ -55,7 +54,7 @@ static void atmel_ecdh_done(struct atmel if (status) goto free_work_data; - /* might want less than we've got */ + /* copy only as much as requested, capped at 32 bytes */ n_sz = min(ATMEL_ECC_NIST_P256_N_SIZE, req->dst_len); /* copy the shared secret */ @@ -64,15 +63,15 @@ static void atmel_ecdh_done(struct atmel if (copied != n_sz) status = -EINVAL; - /* fall through */ free_work_data: kfree_sensitive(work_data); kpp_request_complete(req, status); } /* - * A random private key is generated and stored in the device. The device - * returns the pair public key. + * If no private key is provided, generate one in the device and cache + * the corresponding public key. The generated private key never leaves + * the device. */ static int atmel_ecdh_set_secret(struct crypto_kpp *tfm, const void *buf, unsigned int len) @@ -83,9 +82,7 @@ static int atmel_ecdh_set_secret(struct struct ecdh params; int ret = -ENOMEM; - /* free the old public key, if any */ kfree(ctx->public_key); - /* make sure you don't free the old public key twice */ ctx->public_key = NULL; if (crypto_ecdh_decode_key(buf, len, ¶ms) < 0) { @@ -94,7 +91,6 @@ static int atmel_ecdh_set_secret(struct } if (params.key_size) { - /* fallback to ecdh software implementation */ ctx->do_fallback = true; return crypto_kpp_set_secret(ctx->fallback, buf, len); } @@ -103,11 +99,6 @@ static int atmel_ecdh_set_secret(struct if (!cmd) return -ENOMEM; - /* - * The device only supports NIST P256 ECC keys. The public key size will - * always be the same. Use a macro for the key size to avoid unnecessary - * computations. - */ public_key = kmalloc(ATMEL_ECC_PUBKEY_SIZE, GFP_KERNEL); if (!public_key) goto free_cmd; @@ -120,7 +111,6 @@ static int atmel_ecdh_set_secret(struct if (ret) goto free_public_key; - /* save the public key */ memcpy(public_key, &cmd->data[RSP_DATA_IDX], ATMEL_ECC_PUBKEY_SIZE); ctx->public_key = public_key; @@ -149,7 +139,7 @@ static int atmel_ecdh_generate_public_ke if (!ctx->public_key) return -EINVAL; - /* might want less than we've got */ + /* copy only as much as requested, capped at 64 bytes */ nbytes = min(ATMEL_ECC_PUBKEY_SIZE, req->dst_len); /* public key was saved at private key generation */ @@ -175,7 +165,7 @@ static int atmel_ecdh_compute_shared_sec return crypto_kpp_compute_shared_secret(req); } - /* must have exactly two points to be on the curve */ + /* A P-256 public key must contain two 32-byte coordinates */ if (req->src_len != ATMEL_ECC_PUBKEY_SIZE) return -EINVAL;