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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1783523073; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=N0tnrtHNCdPPaeil/2FJ7xhWeZJlpBvAHaqYCxTjbds=; b=hUqtXPlCKELHA6EiN9LfGfbVZe4c7bDuZoHBgOwhbzi72GRUinJRiobYqhbd/jB69TgpCU 8ruYxUGJpT6Umayo14BjAa/WAKGrtjcJUBr2/RxhA/o6dtB6FTwQ6h2kkEurFMzvOVlz71 GbUIvRFoXa2Ntr6oXNd2vuc4M8jkNDo= From: Thorsten Blum To: Thorsten Blum , Herbert Xu , "David S. Miller" , Nicolas Ferre , Alexandre Belloni , Claudiu Beznea Cc: linux-crypto@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH] crypto: atmel-sha204a - clear RNG data from memory Date: Wed, 8 Jul 2026 17:04:00 +0200 Message-ID: <20260708150359.545852-2-thorsten.blum@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2157; i=thorsten.blum@linux.dev; h=from:subject; bh=q6WzhvHEK1zBLo09d+1w9A+q4i17hzUyPxyhhhNLWOw=; b=owGbwMvMwCUWt7pQ4caZUj3G02pJDFl+afc5ply5Gz+/81i136fpd7unxxkaGBaG3z2zJu7Vu i/3A9YKdZSyMIhxMciKKbI8mPVjhm9pTeUmk4idMHNYmUCGMHBxCsBEJjowMjT3b2z7njlNdvpB rmj3EpuOgM7jv+81Oq4tnj5B2MjIwJmR4U+j5oRbjI4ch1JWbbdb95dp4Z/tQmtMuj92HNvazJ7 Lyg8A X-Developer-Key: i=thorsten.blum@linux.dev; a=openpgp; fpr=1D60735E8AEF3BE473B69D84733678FD8DFEEAD4 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT In atmel_sha204a_rng_read(), use memzero_explicit() to clear the local stack variable cmd before it goes out of scope, since cmd.data may still hold the last 32 random bytes. Since atmel_sha204a_rng_done() caches work_data in hwrng::priv, and its response data is later used as RNG entropy, use kfree_sensitive() to clear the cached data on transaction failure and device removal. Signed-off-by: Thorsten Blum --- drivers/crypto/atmel-sha204a.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/drivers/crypto/atmel-sha204a.c b/drivers/crypto/atmel-sha204a.c index 5eb76245347d..21a84c29c9b7 100644 --- a/drivers/crypto/atmel-sha204a.c +++ b/drivers/crypto/atmel-sha204a.c @@ -15,6 +15,7 @@ #include #include #include +#include #include #include #include "atmel-i2c.h" @@ -35,7 +36,7 @@ static void atmel_sha204a_rng_done(struct atmel_i2c_work_data *work_data, dev_warn_ratelimited(&i2c_priv->client->dev, "i2c transaction failed (%d)\n", status); - kfree(work_data); + kfree_sensitive(work_data); atomic_dec(&i2c_priv->tfm_count); return; } @@ -95,12 +96,15 @@ static int atmel_sha204a_rng_read(struct hwrng *rng, void *data, size_t max, ret = atmel_i2c_send_receive(i2c_priv->client, &cmd); if (ret) - return ret; + goto out; max = min(RANDOM_RSP_SIZE - CMD_OVERHEAD_SIZE, max); memcpy(data, &cmd.data[RSP_DATA_IDX], max); + ret = max; - return max; +out: + memzero_explicit(&cmd, sizeof(cmd)); + return ret; } static int atmel_sha204a_otp_read(struct i2c_client *client, u16 addr, u8 *otp) @@ -209,7 +213,7 @@ static void atmel_sha204a_remove(struct i2c_client *client) devm_hwrng_unregister(&client->dev, &i2c_priv->hwrng); atmel_i2c_flush_queue(); - kfree((void *)i2c_priv->hwrng.priv); + kfree_sensitive((void *)i2c_priv->hwrng.priv); } static const struct of_device_id atmel_sha204a_dt_ids[] = { base-commit: e264401ce4776a288524e5b87593d4d864147115