[PATCH 6.1 0520/1191] crypto: atmel-ecc - reject hardware ECDH without a public key

6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Thorsten Blum <redacted>

[ Upstream commit f240f9b588f4e2de89822adebf560a96b5d263ed ]

The hardware ECDH path in atmel_ecdh_compute_shared_secret() uses the
private key stored in the device. However, the public key is cached only
after atmel_ecdh_set_secret() successfully generated that private key
for the current tfm.

atmel_ecdh_generate_public_key() already rejects requests when no public
key is cached. Add the same check to atmel_ecdh_compute_shared_secret()
to prevent the device from using a private key that was not generated
for the current tfm.

Fixes: 11105693fa05 ("crypto: atmel-ecc - introduce Microchip / Atmel ECC driver")
Signed-off-by: Thorsten Blum <redacted>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/crypto/atmel-ecc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/crypto/atmel-ecc.c b/drivers/crypto/atmel-ecc.c
index 8bc22af2c3c50..d2c830cb20eed 100644
--- a/drivers/crypto/atmel-ecc.c
+++ b/drivers/crypto/atmel-ecc.c

@@ -165,6 +165,9 @@ static int atmel_ecdh_compute_shared_secret(struct kpp_request *req)
 		return crypto_kpp_compute_shared_secret(req);
 	}
 
+	if (!ctx->public_key)
+		return -EINVAL;
+
 	/* A P-256 public key must contain two 32-byte coordinates */
 	if (req->src_len != ATMEL_ECC_PUBKEY_SIZE)
 		return -EINVAL;

-- 
2.53.0