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 22A21422558 for ; Mon, 20 Jul 2026 13:51:06 +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=1784555468; cv=none; b=qntJPxdcV/0Yplp/o9Qq/xRDhfIkyANX+i6YKdj9B+U3mCuIMH1DZHtmhsIq9lP7qwJ+wNK8ilGsmwmCjLtTjqQE+lSx5N2VQoXfF3rhLm83B65l+ud2dN4xRpyy+NnRWClKrMEIbmwDzQkNAZeRrvpJ7Okf7eKIQhxcwipaafk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784555468; c=relaxed/simple; bh=Fwlgx2+4FeE0SAd9W+wwxJ1YDBBXzTcgKkomhyPQSNA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ApwlVX8Jrq9PRnGoGA0R6ySV5paxksGw9BE0vKDvCsI6pscnQySRqrugopuIYRr1htlwdYJURT6rcKM+XuMN6bigASJ60R2dRVt9V8NB304hbbW3ICFIA8h9VdaxdQUCG15c8qRb6sgGK4hSFFfBROWDjYWIfO0K1S8Xcwoo8Kg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VXO9W3DU; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="VXO9W3DU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 372E21F000E9; Mon, 20 Jul 2026 13:51:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784555466; bh=bwb4SBGQ2YiPgYw3Ei42K5F49eDYPafa8z87P5ZB/tQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=VXO9W3DUQylcoFTh2K5I555AQ6Nt7JrPi3jkkWRuh9y+jmLcxpA4fDPmUoD6a71+5 rVZAR6wfg1LlugIRyLOH0MG2B0e7Bi6Sb/3QQ3Qn4iZq+0ggPnDtXbs6z9Cjsd2sH2 6fPSQX/yj/d8+KoLao7bInJIuTykjSRTYhILy6Lhp5g9x84AEIOOWYt+CqvSnJuAyO ncOyx0IOFpqtMyWiozYC+5088ULw//wo6I6/nSimFNTzx90YCNFJYbl56MaRm132qf YTY1YJG7W/KbYpnU6aoJGuxsIa9XhXIDrxHZYXlBWP2OogMek/IEYxujCm5EL7Zv6r mCE0innG3giQw== From: Sasha Levin To: stable@vger.kernel.org Cc: Thorsten Blum , Ard Biesheuvel , Herbert Xu , Sasha Levin Subject: [PATCH 6.1.y 3/3] crypto: atmel-sha204a - drop hwrng quality reduction for ATSHA204A Date: Mon, 20 Jul 2026 09:51:03 -0400 Message-ID: <20260720135103.1306043-3-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260720135103.1306043-1-sashal@kernel.org> References: <2026071513-flatness-crepe-f5ee@gregkh> <20260720135103.1306043-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Thorsten Blum [ Upstream commit ea5e57cc97185329dcc5ebdcaae7e1500bf0ad0b ] Commit 8006aff15516 ("crypto: atmel-sha204a - Set hwrng quality to lowest possible") reduced the hwrng quality to 1 based on a review by Bill Cox [1]. However, despite its title, the review only tested the ATSHA204, not the ATSHA204A. In the same thread, Atmel engineer Landon Cox wrote "this behavior has been eliminated entirely"[2] in the ATSHA204A and "this problem does not affect the ATECC108 or the ATECC108A (or the ATSHA204A)"[3]. According to the official ATSHA204A datasheet [4], the device contains a high-quality hardware RNG that combines its output with an internal seed value stored in EEPROM or SRAM to generate random numbers. The device also implements all security functions using SHA-256, and the driver uses the chip's Random command in seed-update mode. Keep 'quality = 1' for ATSHA204, but drop the explicit hwrng quality reduction for ATSHA204A and fall back to the hwrng core default. [1] https://www.metzdowd.com/pipermail/cryptography/2014-December/023858.html [2] https://www.metzdowd.com/pipermail/cryptography/2014-December/023852.html [3] https://www.metzdowd.com/pipermail/cryptography/2014-December/023886.html [4] https://ww1.microchip.com/downloads/en/DeviceDoc/ATSHA204A-Data-Sheet-40002025A.pdf Fixes: 8006aff15516 ("crypto: atmel-sha204a - Set hwrng quality to lowest possible") Cc: stable@vger.kernel.org Signed-off-by: Thorsten Blum Reviewed-by: Ard Biesheuvel Signed-off-by: Herbert Xu Signed-off-by: Sasha Levin --- drivers/crypto/atmel-sha204a.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) diff --git a/drivers/crypto/atmel-sha204a.c b/drivers/crypto/atmel-sha204a.c index 45703bc3b40337..270f6ab71d979b 100644 --- a/drivers/crypto/atmel-sha204a.c +++ b/drivers/crypto/atmel-sha204a.c @@ -18,6 +18,12 @@ #include #include "atmel-i2c.h" +/* + * According to review by Bill Cox [1], the ATSHA204 has very low entropy. + * [1] https://www.metzdowd.com/pipermail/cryptography/2014-December/023858.html + */ +static const unsigned short atsha204_quality = 1; + static void atmel_sha204a_rng_done(struct atmel_i2c_work_data *work_data, void *areq, int status) { @@ -96,6 +102,7 @@ static int atmel_sha204a_probe(struct i2c_client *client, const struct i2c_device_id *id) { struct atmel_i2c_client_priv *i2c_priv; + const unsigned short *quality; int ret; ret = atmel_i2c_probe(client, id); @@ -109,11 +116,9 @@ static int atmel_sha204a_probe(struct i2c_client *client, i2c_priv->hwrng.name = dev_name(&client->dev); i2c_priv->hwrng.read = atmel_sha204a_rng_read; - /* - * According to review by Bill Cox [1], this HWRNG has very low entropy. - * [1] https://www.metzdowd.com/pipermail/cryptography/2014-December/023858.html - */ - i2c_priv->hwrng.quality = 1; + quality = i2c_get_match_data(client); + if (quality) + i2c_priv->hwrng.quality = *quality; ret = devm_hwrng_register(&client->dev, &i2c_priv->hwrng); if (ret) @@ -133,14 +138,14 @@ static void atmel_sha204a_remove(struct i2c_client *client) } static const struct of_device_id atmel_sha204a_dt_ids[] __maybe_unused = { - { .compatible = "atmel,atsha204", }, + { .compatible = "atmel,atsha204", .data = &atsha204_quality }, { .compatible = "atmel,atsha204a", }, { /* sentinel */ } }; MODULE_DEVICE_TABLE(of, atmel_sha204a_dt_ids); static const struct i2c_device_id atmel_sha204a_id[] = { - { "atsha204" }, + { "atsha204", (kernel_ulong_t)&atsha204_quality }, { "atsha204a" }, { /* sentinel */ } }; -- 2.53.0