FAILED: patch "[PATCH] crypto: atmel-ecc - avoid stale fallback key after set_secret" failed to apply to 5.15-stable tree

FAILED: patch "[PATCH] crypto: atmel-ecc - avoid stale fallback key after set_secret" failed to apply to 5.15-stable tree

[gregkh]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x f07a0d251db7606e4792d2610788fbcc7b2c0d12
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026083113-trough-translate-08c1@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f07a0d251db7606e4792d2610788fbcc7b2c0d12 Mon Sep 17 00:00:00 2001
From: Thorsten Blum <thorsten.blum@linux.dev>
Date: Wed, 8 Jul 2026 22:42:48 +0200
Subject: [PATCH] crypto: atmel-ecc - avoid stale fallback key after set_secret
 failure

Clear ->do_fallback before decoding a new ECDH secret and enable it only
after the software fallback accepts a caller-provided private key. This
avoids using a stale fallback key should crypto_kpp_set_secret() fail.

Fixes: 11105693fa05 ("crypto: atmel-ecc - introduce Microchip / Atmel ECC driver")
Cc: stable@vger.kernel.org
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/drivers/crypto/atmel-ecc.c b/drivers/crypto/atmel-ecc.c
index 8e13aeccf011..4add3b2ddd0b 100644
--- a/drivers/crypto/atmel-ecc.c
+++ b/drivers/crypto/atmel-ecc.c
@@ -82,6 +82,7 @@ static int atmel_ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
 
 	kfree(ctx->public_key);
 	ctx->public_key = NULL;
+	ctx->do_fallback = false;
 
 	if (crypto_ecdh_decode_key(buf, len, &params) < 0) {
 		dev_err(&ctx->client->dev, "crypto_ecdh_decode_key failed\n");
@@ -89,8 +90,9 @@ static int atmel_ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
 	}
 
 	if (params.key_size) {
-		ctx->do_fallback = true;
-		return crypto_kpp_set_secret(ctx->fallback, buf, len);
+		ret = crypto_kpp_set_secret(ctx->fallback, buf, len);
+		ctx->do_fallback = !ret;
+		return ret;
 	}
 
 	cmd = kmalloc_obj(*cmd);
@@ -101,8 +103,6 @@ static int atmel_ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
 	if (!public_key)
 		goto free_cmd;
 
-	ctx->do_fallback = false;
-
 	atmel_i2c_init_genkey_cmd(cmd, DATA_SLOT_2);
 
 	ret = atmel_i2c_send_receive(ctx->client, cmd);

[PATCH 5.15.y 1/3] crypto: atmel-ecc - replace min_t with min

[Sasha Levin]

From: Thorsten Blum <thorsten.blum@linux.dev>

[ Upstream commit 5b085b2a038a1458f9398cb3b3b03cba6e38e1e0 ]

Use the simpler min() macro since the values are all unsigned and
compatible.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Reviewed-by: David Laight <david.laght.linux@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Stable-dep-of: f07a0d251db7 ("crypto: atmel-ecc - avoid stale fallback key after set_secret failure")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/crypto/atmel-ecc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/crypto/atmel-ecc.c b/drivers/crypto/atmel-ecc.c
index 004d87cbfa221..e21466dfd0753 100644
--- a/drivers/crypto/atmel-ecc.c
+++ b/drivers/crypto/atmel-ecc.c
@@ -56,7 +56,7 @@ static void atmel_ecdh_done(struct atmel_i2c_work_data *work_data, void *areq,
 		goto free_work_data;
 
 	/* might want less than we've got */
-	n_sz = min_t(size_t, ATMEL_ECC_NIST_P256_N_SIZE, req->dst_len);
+	n_sz = min(ATMEL_ECC_NIST_P256_N_SIZE, req->dst_len);
 
 	/* copy the shared secret */
 	copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst, n_sz),
@@ -150,7 +150,7 @@ static int atmel_ecdh_generate_public_key(struct kpp_request *req)
 		return -EINVAL;
 
 	/* might want less than we've got */
-	nbytes = min_t(size_t, ATMEL_ECC_PUBKEY_SIZE, req->dst_len);
+	nbytes = min(ATMEL_ECC_PUBKEY_SIZE, req->dst_len);
 
 	/* public key was saved at private key generation */
 	copied = sg_copy_from_buffer(req->dst,
-- 
2.53.0

[PATCH 5.15.y 2/3] crypto: atmel-ecc - clean up and improve ECDH comments

[Sasha Levin]

From: Thorsten Blum <thorsten.blum@linux.dev>

[ 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 <thorsten.blum@linux.dev>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Stable-dep-of: f07a0d251db7 ("crypto: atmel-ecc - avoid stale fallback key after set_secret failure")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/crypto/atmel-ecc.c | 38 ++++++++++++++------------------------
 1 file changed, 14 insertions(+), 24 deletions(-)

diff --git a/drivers/crypto/atmel-ecc.c b/drivers/crypto/atmel-ecc.c
index e21466dfd0753..7950e635277a5 100644
--- a/drivers/crypto/atmel-ecc.c
+++ b/drivers/crypto/atmel-ecc.c
@@ -27,15 +27,14 @@ static struct atmel_ecc_driver_data driver_data;
 
 /**
  * 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_i2c_work_data *work_data, void *areq,
 	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_i2c_work_data *work_data, void *areq,
 	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 crypto_kpp *tfm, const void *buf,
 	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, &params) < 0) {
@@ -94,7 +91,6 @@ static int atmel_ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
 	}
 
 	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 crypto_kpp *tfm, const void *buf,
 	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 crypto_kpp *tfm, const void *buf,
 	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_key(struct kpp_request *req)
 	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_secret(struct kpp_request *req)
 		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;
 
-- 
2.53.0

[PATCH 5.15.y 3/3] crypto: atmel-ecc - avoid stale fallback key after set_secret failure

[Sasha Levin]

From: Thorsten Blum <thorsten.blum@linux.dev>

[ Upstream commit f07a0d251db7606e4792d2610788fbcc7b2c0d12 ]

Clear ->do_fallback before decoding a new ECDH secret and enable it only
after the software fallback accepts a caller-provided private key. This
avoids using a stale fallback key should crypto_kpp_set_secret() fail.

Fixes: 11105693fa05 ("crypto: atmel-ecc - introduce Microchip / Atmel ECC driver")
Cc: stable@vger.kernel.org
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/crypto/atmel-ecc.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/crypto/atmel-ecc.c b/drivers/crypto/atmel-ecc.c
index 7950e635277a5..415970cecb329 100644
--- a/drivers/crypto/atmel-ecc.c
+++ b/drivers/crypto/atmel-ecc.c
@@ -84,6 +84,7 @@ static int atmel_ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
 
 	kfree(ctx->public_key);
 	ctx->public_key = NULL;
+	ctx->do_fallback = false;
 
 	if (crypto_ecdh_decode_key(buf, len, &params) < 0) {
 		dev_err(&ctx->client->dev, "crypto_ecdh_decode_key failed\n");
@@ -91,8 +92,9 @@ static int atmel_ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
 	}
 
 	if (params.key_size) {
-		ctx->do_fallback = true;
-		return crypto_kpp_set_secret(ctx->fallback, buf, len);
+		ret = crypto_kpp_set_secret(ctx->fallback, buf, len);
+		ctx->do_fallback = !ret;
+		return ret;
 	}
 
 	cmd = kmalloc(sizeof(*cmd), GFP_KERNEL);
@@ -103,8 +105,6 @@ static int atmel_ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
 	if (!public_key)
 		goto free_cmd;
 
-	ctx->do_fallback = false;
-
 	atmel_i2c_init_genkey_cmd(cmd, DATA_SLOT_2);
 
 	ret = atmel_i2c_send_receive(ctx->client, cmd);
-- 
2.53.0