[PATCH] [v2] crypto: inside-secure

* [PATCH] [v2] crypto: inside-secure - Reduce stack usage
@ 2019-10-22 15:14 Arnd Bergmann
  2019-11-01  5:39 ` Herbert Xu
  0 siblings, 1 reply; 2+ messages in thread
From: Arnd Bergmann @ 2019-10-22 15:14 UTC (permalink / raw)
  To: Antoine Tenart, Herbert Xu, David S. Miller
  Cc: Arnd Bergmann, Pascal van Leeuwen, Pascal van Leeuwen,
	Ard Biesheuvel, linux-crypto, linux-kernel

safexcel_aead_setkey() contains three large stack variables, totalling
slightly more than the 1024 byte warning limit:

drivers/crypto/inside-secure/safexcel_cipher.c:303:12: error: stack frame size of 1032 bytes in function 'safexcel_aead_setkey' [-Werror,-Wframe-larger-than=]

The function already contains a couple of dynamic allocations, so it is
likely not performance critical and it can only be called in a context
that allows sleeping, so the easiest workaround is to add change it
to use dynamic allocations. Combining istate and ostate into a single
variable simplifies the allocation at the cost of making it slightly
less readable.

Alternatively, it should be possible to shrink these allocations
as the extra buffers appear to be largely unnecessary, but doing
this would be a much more invasive change.

Fixes: 0e17e3621a28 ("crypto: inside-secure - add support for authenc(hmac(sha*),rfc3686(ctr(aes))) suites")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
v2: rebase against crypto/master
---
 .../crypto/inside-secure/safexcel_cipher.c    | 55 ++++++++++++-------
 1 file changed, 36 insertions(+), 19 deletions(-)

diff --git a/drivers/crypto/inside-secure/safexcel_cipher.c b/drivers/crypto/inside-secure/safexcel_cipher.c
index 407ebcd8d71f..1aade2fd6f1e 100644
--- a/drivers/crypto/inside-secure/safexcel_cipher.c
+++ b/drivers/crypto/inside-secure/safexcel_cipher.c
@@ -354,10 +354,10 @@ static int safexcel_aead_setkey(struct crypto_aead *ctfm, const u8 *key,
 {
 	struct crypto_tfm *tfm = crypto_aead_tfm(ctfm);
 	struct safexcel_cipher_ctx *ctx = crypto_tfm_ctx(tfm);
-	struct safexcel_ahash_export_state istate, ostate;
+	struct safexcel_ahash_export_state *state;
 	struct safexcel_crypto_priv *priv = ctx->priv;
+	struct crypto_aes_ctx *aes;
 	struct crypto_authenc_keys keys;
-	struct crypto_aes_ctx aes;
 	int err = -EINVAL;
 
 	if (unlikely(crypto_authenc_extractkeys(&keys, key, len)))
@@ -387,7 +387,14 @@ static int safexcel_aead_setkey(struct crypto_aead *ctfm, const u8 *key,
 			goto badkey_expflags;
 		break;
 	case SAFEXCEL_AES:
-		err = aes_expandkey(&aes, keys.enckey, keys.enckeylen);
+		aes = kzalloc(sizeof(*aes), GFP_KERNEL);
+		if (!aes) {
+			err = -ENOMEM;
+			goto badkey;
+		}
+
+		err = aes_expandkey(aes, keys.enckey, keys.enckeylen);
+		kfree(aes);
 		if (unlikely(err))
 			goto badkey;
 		break;
@@ -404,61 +411,71 @@ static int safexcel_aead_setkey(struct crypto_aead *ctfm, const u8 *key,
 	    memcmp(ctx->key, keys.enckey, keys.enckeylen))
 		ctx->base.needs_inv = true;
 
+	state = kzalloc(sizeof(struct safexcel_ahash_export_state) * 2, GFP_KERNEL);
+	if (!state) {
+		err = -ENOMEM;
+		goto badkey;
+	}
+
 	/* Auth key */
 	switch (ctx->hash_alg) {
 	case CONTEXT_CONTROL_CRYPTO_ALG_SHA1:
 		if (safexcel_hmac_setkey("safexcel-sha1", keys.authkey,
-					 keys.authkeylen, &istate, &ostate))
-			goto badkey;
+					 keys.authkeylen, &state[0], &state[1]))
+			goto badkey_free;
 		break;
 	case CONTEXT_CONTROL_CRYPTO_ALG_SHA224:
 		if (safexcel_hmac_setkey("safexcel-sha224", keys.authkey,
-					 keys.authkeylen, &istate, &ostate))
-			goto badkey;
+					 keys.authkeylen, &state[0], &state[1]))
+			goto badkey_free;
 		break;
 	case CONTEXT_CONTROL_CRYPTO_ALG_SHA256:
 		if (safexcel_hmac_setkey("safexcel-sha256", keys.authkey,
-					 keys.authkeylen, &istate, &ostate))
-			goto badkey;
+					 keys.authkeylen, &state[0], &state[1]))
+			goto badkey_free;
 		break;
 	case CONTEXT_CONTROL_CRYPTO_ALG_SHA384:
 		if (safexcel_hmac_setkey("safexcel-sha384", keys.authkey,
-					 keys.authkeylen, &istate, &ostate))
-			goto badkey;
+					 keys.authkeylen, &state[0], &state[1]))
+			goto badkey_free;
 		break;
 	case CONTEXT_CONTROL_CRYPTO_ALG_SHA512:
 		if (safexcel_hmac_setkey("safexcel-sha512", keys.authkey,
-					 keys.authkeylen, &istate, &ostate))
-			goto badkey;
+					 keys.authkeylen, &state[0], &state[1]))
+			goto badkey_free;
 		break;
 	case CONTEXT_CONTROL_CRYPTO_ALG_SM3:
 		if (safexcel_hmac_setkey("safexcel-sm3", keys.authkey,
-					 keys.authkeylen, &istate, &ostate))
+					 keys.authkeylen, &state[0], &state[1]))
 			goto badkey;
 		break;
 	default:
 		dev_err(priv->dev, "aead: unsupported hash algorithm\n");
-		goto badkey;
+		goto badkey_free;
 	}
 
 	crypto_aead_set_flags(ctfm, crypto_aead_get_flags(ctfm) &
 				    CRYPTO_TFM_RES_MASK);
 
 	if (priv->flags & EIP197_TRC_CACHE && ctx->base.ctxr_dma &&
-	    (memcmp(ctx->ipad, istate.state, ctx->state_sz) ||
-	     memcmp(ctx->opad, ostate.state, ctx->state_sz)))
+	    (memcmp(ctx->ipad, &state[0].state, ctx->state_sz) ||
+	     memcmp(ctx->opad, &state[1].state, ctx->state_sz)))
 		ctx->base.needs_inv = true;
 
 	/* Now copy the keys into the context */
 	memcpy(ctx->key, keys.enckey, keys.enckeylen);
 	ctx->key_len = keys.enckeylen;
 
-	memcpy(ctx->ipad, &istate.state, ctx->state_sz);
-	memcpy(ctx->opad, &ostate.state, ctx->state_sz);
+	memcpy(ctx->ipad, &state[0].state, ctx->state_sz);
+	memcpy(ctx->opad, &state[1].state, ctx->state_sz);
 
 	memzero_explicit(&keys, sizeof(keys));
+	kfree(state);
+
 	return 0;
 
+badkey_free:
+	kfree(state);
 badkey:
 	crypto_aead_set_flags(ctfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
 badkey_expflags:
-- 
2.20.0


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