[PATCH 7.2.y 2/2] crypto: atmel-ecc - avoid stale fallback key after set_secret failure

[Sasha Levin <sashal@kernel.org>]

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 87e25696400df..4dc34c5bc0f6c 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_obj(*cmd);
@@ -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