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 38D2C2E7366 for ; Mon, 20 Jul 2026 15:00:55 +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=1784559656; cv=none; b=taThlqvouyZiWislsUnSS5Matr5XTTfPD3zUY0TYMunXFg0OZULkm+DamggFjg4b5NzaW5cUaj+qq6oqIZ6H+q1mHxdchrBkRuCsfW/VtqG8AxtSVsm628l36iWoW80jQpA1pEPcPV9eQQ1AJ5lYcZb8v1y7HLLIaLMuC7Su/5c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784559656; c=relaxed/simple; bh=O2ZjQOwkW9wHi+jGpkN69UUYN9M7DRncU3CFIIlssn8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=k2Q3jnmPvQcHlRf3z5AH/gZzUEXoO9qOogQC75VYua1aLjf60CpDSLCvS7RB5A5gNkrLWz01SftSacOLudCqkySq5bRQ7F/7A5Q/q8YVaFoDhc6F6e3rYqYUvUt/TSi6w7JZaLZttfGsExMZYWNGA3GuN9qML4OIMUEhEs9HhCg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CqzgxvoR; 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="CqzgxvoR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 69F591F00A3E; Mon, 20 Jul 2026 15:00:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784559655; bh=tuHCDEZhdyotNk2mxTj7wkruGxzXHzseHMEeQwEZa5Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=CqzgxvoRxld+Rr/0irvDeksqIsYRJfpGhIP5P9Nn+5gAnvVa3bISEslAa8dHNxpoR n/gm31ThelqWmcqqI2J4J91025167CM39NFRgcMD/r8OSSGpeSul070sAAKY+oMSoY To6BZER4/405sUeUmk0QdbpwS7xqr9SjKNjCuFDz9bcYEkbDZueFHJD/YzFjQJjtI+ XBdfmou8JfeIFFzVKUu1WIo6+en4WMqpL2wgIgY4XGvTvkkGVCnyY+JHHqUpb9z/uP suNCMFSdpYonyUs7eCAWBn5ZQs6XriA5hBT4JuMOGc00Jl2kq02jqvHkuoW5Ii/yBz LZO9J1woCi3Lg== From: Sasha Levin To: stable@vger.kernel.org Cc: Thorsten Blum , Ard Biesheuvel , Herbert Xu , Sasha Levin Subject: [PATCH 5.15.y 3/3] crypto: atmel-sha204a - drop hwrng quality reduction for ATSHA204A Date: Mon, 20 Jul 2026 11:00:51 -0400 Message-ID: <20260720150051.1918796-3-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260720150051.1918796-1-sashal@kernel.org> References: <2026071513-seducing-second-a53b@gregkh> <20260720150051.1918796-1-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 77c0968b696337..040bed27c7d544 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) { @@ -95,6 +101,7 @@ 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); @@ -108,11 +115,9 @@ 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) @@ -137,14 +142,14 @@ static int 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