Hello Ard,

Quoting Ard Biesheuvel (2020-06-25 09:18:16)

The skcipher API dynamically instantiates the transformation object on request that implements the requested algorithm optimally on the given platform. This notion of optimality only matters for cases like bulk network or disk encryption, where performance can be a bottleneck, or in cases where the algorithm itself is not known at compile time.

In the mscc case, we are dealing with AES encryption of a single block, and so neither concern applies, and we are better off using the AES library interface, which is lightweight and safe for this kind of use.

Note that the scatterlist API does not permit references to buffers that are located on the stack, so the existing code is incorrect in any case, but avoiding the skcipher and scatterlist APIs entirely is the most straight-forward approach to fixing this.

Cc: Antoine Tenart antoine.tenart@bootlin.com Cc: Andrew Lunn andrew@lunn.ch Cc: Florian Fainelli f.fainelli@gmail.com Cc: Heiner Kallweit hkallweit1@gmail.com Cc: "David S. Miller" davem@davemloft.net Cc: Jakub Kicinski kuba@kernel.org Cc: stable@vger.kernel.org Fixes: 28c5107aa904e ("net: phy: mscc: macsec support") Reviewed-by: Eric Biggers ebiggers@google.com Signed-off-by: Ard Biesheuvel ardb@kernel.org

Tested-by: Antoine Tenart antoine.tenart@bootlin.com

That improves and simplifies a lot the code, thank you! Antoine

---

v2:

• select CRYPTO_LIB_AES only if MACSEC is enabled
• add Eric's R-b

drivers/net/phy/Kconfig | 3 +- drivers/net/phy/mscc/mscc_macsec.c | 40 +++++--------------- 2 files changed, 10 insertions(+), 33 deletions(-)

diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig index f25702386d83..e351d65533aa 100644 --- a/drivers/net/phy/Kconfig +++ b/drivers/net/phy/Kconfig @@ -480,8 +480,7 @@ config MICROCHIP_T1_PHY config MICROSEMI_PHY tristate "Microsemi PHYs" depends on MACSEC || MACSEC=n

•   select CRYPTO_AES
  

•   select CRYPTO_ECB
  

•   select CRYPTO_LIB_AES if MACSEC
    help
      Currently supports VSC8514, VSC8530, VSC8531, VSC8540 and VSC8541 PHYs
  

diff --git a/drivers/net/phy/mscc/mscc_macsec.c b/drivers/net/phy/mscc/mscc_macsec.c index b4d3dc4068e2..d53ca884b5c9 100644 --- a/drivers/net/phy/mscc/mscc_macsec.c +++ b/drivers/net/phy/mscc/mscc_macsec.c @@ -10,7 +10,7 @@ #include <linux/phy.h> #include <dt-bindings/net/mscc-phy-vsc8531.h> -#include <crypto/skcipher.h> +#include <crypto/aes.h> #include <net/macsec.h> @@ -500,39 +500,17 @@ static u32 vsc8584_macsec_flow_context_id(struct macsec_flow *flow) static int vsc8584_macsec_derive_key(const u8 key[MACSEC_KEYID_LEN], u16 key_len, u8 hkey[16]) {

•   struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);
  

•   struct skcipher_request *req = NULL;
  

•   struct scatterlist src, dst;
  

•   DECLARE_CRYPTO_WAIT(wait);
  

•   u32 input[4] = {0};
  

•   const u8 input[AES_BLOCK_SIZE] = {0};
  

•   struct crypto_aes_ctx ctx;
    int ret;
  

•   if (IS_ERR(tfm))
  

•           return PTR_ERR(tfm);
  

•   req = skcipher_request_alloc(tfm, GFP_KERNEL);
  

•   if (!req) {
  

•           ret = -ENOMEM;
  

•           goto out;
  

•   }
  

•   skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
  

•                                 CRYPTO_TFM_REQ_MAY_SLEEP, crypto_req_done,
  

•                                 &wait);
  

•   ret = crypto_skcipher_setkey(tfm, key, key_len);
  

•   if (ret < 0)
  

•           goto out;
  

•   sg_init_one(&src, input, 16);
  

•   sg_init_one(&dst, hkey, 16);
  

•   skcipher_request_set_crypt(req, &src, &dst, 16, NULL);
  

•   ret = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
  

•   ret = aes_expandkey(&ctx, key, key_len);
  

•   if (ret)
  

•           return ret;
  

-out:

•   skcipher_request_free(req);
  

•   crypto_free_skcipher(tfm);
  

•   return ret;
  

•   aes_encrypt(&ctx, hkey, input);
  

•   memzero_explicit(&ctx, sizeof(ctx));
  

•   return 0;
  

} static int vsc8584_macsec_transformation(struct phy_device *phydev, -- 2.27.0