linux-kernel - [PATCH] crypto: ccree - reduce kernel stack usage with clang

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Message-Id: <20190314090951.840339-1-arnd@arndb.de>
Date:   Thu, 14 Mar 2019 10:09:44 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Gilad Ben-Yossef <gilad@...yossef.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>
Cc:     Arnd Bergmann <arnd@...db.de>, Eric Biggers <ebiggers@...gle.com>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] crypto: ccree - reduce kernel stack usage with clang

Building with clang for a 32-bit architecture runs over the stack
frame limit in the setkey function:

drivers/crypto/ccree/cc_cipher.c:318:12: error: stack frame size of 1152 bytes in function 'cc_cipher_setkey' [-Werror,-Wframe-larger-than=]

The problem is that there are two large variables: the temporary
'tmp' array and the SHASH_DESC_ON_STACK() declaration. Moving
the first into the block in which it is used reduces the
total frame size to 768 bytes, which seems more reasonable
and is under the warning limit.

Fixes: 63ee04c8b491 ("crypto: ccree - add skcipher support")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/crypto/ccree/cc_cipher.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/crypto/ccree/cc_cipher.c b/drivers/crypto/ccree/cc_cipher.c
index d9c17078517b..0abcdc224ab0 100644
--- a/drivers/crypto/ccree/cc_cipher.c
+++ b/drivers/crypto/ccree/cc_cipher.c
@@ -321,7 +321,6 @@ static int cc_cipher_setkey(struct crypto_skcipher *sktfm, const u8 *key,
 	struct crypto_tfm *tfm = crypto_skcipher_tfm(sktfm);
 	struct cc_cipher_ctx *ctx_p = crypto_tfm_ctx(tfm);
 	struct device *dev = drvdata_to_dev(ctx_p->drvdata);
-	u32 tmp[DES3_EDE_EXPKEY_WORDS];
 	struct cc_crypto_alg *cc_alg =
 			container_of(tfm->__crt_alg, struct cc_crypto_alg,
 				     skcipher_alg.base);
@@ -347,6 +346,7 @@ static int cc_cipher_setkey(struct crypto_skcipher *sktfm, const u8 *key,
 	 * HW does the expansion on its own.
 	 */
 	if (ctx_p->flow_mode == S_DIN_to_DES) {
+		u32 tmp[DES3_EDE_EXPKEY_WORDS];
 		if (keylen == DES3_EDE_KEY_SIZE &&
 		    __des3_ede_setkey(tmp, &tfm->crt_flags, key,
 				      DES3_EDE_KEY_SIZE)) {
-- 
2.20.0