crypto: qat - move temp buffers off the stack

Arnd reports that with Kees's latest VLA patches applied, the HMAC
handling in the QAT driver uses a worst case estimate of 160 bytes
for the SHA blocksize, allowing the compiler to determine the size
of the stack frame at compile time and throw a warning:

  drivers/crypto/qat/qat_common/qat_algs.c: In function 'qat_alg_do_precomputes':
  drivers/crypto/qat/qat_common/qat_algs.c:257:1: error: the frame size
  of 1112 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]

Given that this worst case estimate is only 32 bytes larger than the
actual block size of SHA-512, the use of a VLA here was hiding the
excessive size of the stack frame from the compiler, and so we should
try to move these buffers off the stack.

So move the ipad/opad buffers and the various SHA state descriptors
into the tfm context struct. Since qat_alg_do_precomputes() is only
called in the context of a setkey() operation, this should be safe.
Using SHA512_BLOCK_SIZE for the size of the ipad/opad buffers allows
them to be used by SHA-1/SHA-256 as well.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/drivers/crypto/qat/qat_common/qat_algs.c b/drivers/crypto/qat/qat_common/qat_algs.c
index a28edf7..d269829 100644 (file)
--- a/drivers/crypto/qat/qat_common/qat_algs.c
+++ b/drivers/crypto/qat/qat_common/qat_algs.c
@@ -113,6 +113,13 @@ struct qat_alg_aead_ctx {
        struct crypto_shash *hash_tfm;
        enum icp_qat_hw_auth_algo qat_hash_alg;
        struct qat_crypto_instance *inst;
+       union {
+               struct sha1_state sha1;
+               struct sha256_state sha256;
+               struct sha512_state sha512;
+       };
+       char ipad[SHA512_BLOCK_SIZE]; /* sufficient for SHA-1/SHA-256 as well */
+       char opad[SHA512_BLOCK_SIZE];
 };
 
 struct qat_alg_ablkcipher_ctx {
@@ -148,41 +155,32 @@ static int qat_alg_do_precomputes(struct icp_qat_hw_auth_algo_blk *hash,
                                  unsigned int auth_keylen)
 {
        SHASH_DESC_ON_STACK(shash, ctx->hash_tfm);
-       struct sha1_state sha1;
-       struct sha256_state sha256;
-       struct sha512_state sha512;
        int block_size = crypto_shash_blocksize(ctx->hash_tfm);
        int digest_size = crypto_shash_digestsize(ctx->hash_tfm);
-       char ipad[MAX_ALGAPI_BLOCKSIZE];
-       char opad[MAX_ALGAPI_BLOCKSIZE];
        __be32 *hash_state_out;
        __be64 *hash512_state_out;
        int i, offset;
 
-       memset(ipad, 0, block_size);
-       memset(opad, 0, block_size);
+       memset(ctx->ipad, 0, block_size);
+       memset(ctx->opad, 0, block_size);
        shash->tfm = ctx->hash_tfm;
        shash->flags = 0x0;
 
-       if (WARN_ON(block_size > sizeof(ipad) ||
-                   sizeof(ipad) != sizeof(opad)))
-               return -EINVAL;
-
        if (auth_keylen > block_size) {
                int ret = crypto_shash_digest(shash, auth_key,
-                                             auth_keylen, ipad);
+                                             auth_keylen, ctx->ipad);
                if (ret)
                        return ret;
 
-               memcpy(opad, ipad, digest_size);
+               memcpy(ctx->opad, ctx->ipad, digest_size);
        } else {
-               memcpy(ipad, auth_key, auth_keylen);
-               memcpy(opad, auth_key, auth_keylen);
+               memcpy(ctx->ipad, auth_key, auth_keylen);
+               memcpy(ctx->opad, auth_key, auth_keylen);
        }
 
        for (i = 0; i < block_size; i++) {
-               char *ipad_ptr = ipad + i;
-               char *opad_ptr = opad + i;
+               char *ipad_ptr = ctx->ipad + i;
+               char *opad_ptr = ctx->opad + i;
                *ipad_ptr ^= HMAC_IPAD_VALUE;
                *opad_ptr ^= HMAC_OPAD_VALUE;
        }
@@ -190,7 +188,7 @@ static int qat_alg_do_precomputes(struct icp_qat_hw_auth_algo_blk *hash,
        if (crypto_shash_init(shash))
                return -EFAULT;
 
-       if (crypto_shash_update(shash, ipad, block_size))
+       if (crypto_shash_update(shash, ctx->ipad, block_size))
                return -EFAULT;
 
        hash_state_out = (__be32 *)hash->sha.state1;
@@ -198,22 +196,22 @@ static int qat_alg_do_precomputes(struct icp_qat_hw_auth_algo_blk *hash,
 
        switch (ctx->qat_hash_alg) {
        case ICP_QAT_HW_AUTH_ALGO_SHA1:
-               if (crypto_shash_export(shash, &sha1))
+               if (crypto_shash_export(shash, &ctx->sha1))
                        return -EFAULT;
                for (i = 0; i < digest_size >> 2; i++, hash_state_out++)
-                       *hash_state_out = cpu_to_be32(*(sha1.state + i));
+                       *hash_state_out = cpu_to_be32(ctx->sha1.state[i]);
                break;
        case ICP_QAT_HW_AUTH_ALGO_SHA256:
-               if (crypto_shash_export(shash, &sha256))
+               if (crypto_shash_export(shash, &ctx->sha256))
                        return -EFAULT;
                for (i = 0; i < digest_size >> 2; i++, hash_state_out++)
-                       *hash_state_out = cpu_to_be32(*(sha256.state + i));
+                       *hash_state_out = cpu_to_be32(ctx->sha256.state[i]);
                break;
        case ICP_QAT_HW_AUTH_ALGO_SHA512:
-               if (crypto_shash_export(shash, &sha512))
+               if (crypto_shash_export(shash, &ctx->sha512))
                        return -EFAULT;
                for (i = 0; i < digest_size >> 3; i++, hash512_state_out++)
-                       *hash512_state_out = cpu_to_be64(*(sha512.state + i));
+                       *hash512_state_out = cpu_to_be64(ctx->sha512.state[i]);
                break;
        default:
                return -EFAULT;
@@ -222,7 +220,7 @@ static int qat_alg_do_precomputes(struct icp_qat_hw_auth_algo_blk *hash,
        if (crypto_shash_init(shash))
                return -EFAULT;
 
-       if (crypto_shash_update(shash, opad, block_size))
+       if (crypto_shash_update(shash, ctx->opad, block_size))
                return -EFAULT;
 
        offset = round_up(qat_get_inter_state_size(ctx->qat_hash_alg), 8);
@@ -231,28 +229,28 @@ static int qat_alg_do_precomputes(struct icp_qat_hw_auth_algo_blk *hash,
 
        switch (ctx->qat_hash_alg) {
        case ICP_QAT_HW_AUTH_ALGO_SHA1:
-               if (crypto_shash_export(shash, &sha1))
+               if (crypto_shash_export(shash, &ctx->sha1))
                        return -EFAULT;
                for (i = 0; i < digest_size >> 2; i++, hash_state_out++)
-                       *hash_state_out = cpu_to_be32(*(sha1.state + i));
+                       *hash_state_out = cpu_to_be32(ctx->sha1.state[i]);
                break;
        case ICP_QAT_HW_AUTH_ALGO_SHA256:
-               if (crypto_shash_export(shash, &sha256))
+               if (crypto_shash_export(shash, &ctx->sha256))
                        return -EFAULT;
                for (i = 0; i < digest_size >> 2; i++, hash_state_out++)
-                       *hash_state_out = cpu_to_be32(*(sha256.state + i));
+                       *hash_state_out = cpu_to_be32(ctx->sha256.state[i]);
                break;
        case ICP_QAT_HW_AUTH_ALGO_SHA512:
-               if (crypto_shash_export(shash, &sha512))
+               if (crypto_shash_export(shash, &ctx->sha512))
                        return -EFAULT;
                for (i = 0; i < digest_size >> 3; i++, hash512_state_out++)
-                       *hash512_state_out = cpu_to_be64(*(sha512.state + i));
+                       *hash512_state_out = cpu_to_be64(ctx->sha512.state[i]);
                break;
        default:
                return -EFAULT;
        }
-       memzero_explicit(ipad, block_size);
-       memzero_explicit(opad, block_size);
+       memzero_explicit(ctx->ipad, block_size);
+       memzero_explicit(ctx->opad, block_size);
        return 0;
 }