[PATCH v2 2/2] crypto: testmgr - dynamically allocate crypto_shash

[Arnd Bergmann]

The largest stack object in this file is now the shash descriptor.
Since there are many other stack variables, this can push it
over the 1024 byte warning limit, in particular with clang and
KASAN:

crypto/testmgr.c:1693:12: error: stack frame size of 1312 bytes in function '__alg_test_hash' [-Werror,-Wframe-larger-than=]

Make test_hash_vs_generic_impl() do the same thing as the
corresponding eaed and skcipher functions by allocating the
descriptor dynamically. We can still do better than this,
but it brings us well below the 1024 byte limit.

Suggested-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Fixes: 9a8a6b3f0950 ("crypto: testmgr - fuzz hashes against their generic implementation")
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
 crypto/testmgr.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/crypto/testmgr.c b/crypto/testmgr.c
index 0e07f61f1a31..0ce28b3aab3c 100644
--- a/crypto/testmgr.c
+++ b/crypto/testmgr.c
@@ -1503,14 +1503,12 @@ static int test_hash_vec(const char *driver, const struct hash_testvec *vec,
  * Generate a hash test vector from the given implementation.
  * Assumes the buffers in 'vec' were already allocated.
  */
-static void generate_random_hash_testvec(struct crypto_shash *tfm,
+static void generate_random_hash_testvec(struct shash_desc *desc,
 					 struct hash_testvec *vec,
 					 unsigned int maxkeysize,
 					 unsigned int maxdatasize,
 					 char *name, size_t max_namelen)
 {
-	SHASH_DESC_ON_STACK(desc, tfm);
-
 	/* Data */
 	vec->psize = generate_random_length(maxdatasize);
 	generate_random_bytes((u8 *)vec->plaintext, vec->psize);
@@ -1527,7 +1525,7 @@ static void generate_random_hash_testvec(struct crypto_shash *tfm,
 			vec->ksize = 1 + (prandom_u32() % maxkeysize);
 		generate_random_bytes((u8 *)vec->key, vec->ksize);
 
-		vec->setkey_error = crypto_shash_setkey(tfm, vec->key,
+		vec->setkey_error = crypto_shash_setkey(desc->tfm, vec->key,
 							vec->ksize);
 		/* If the key couldn't be set, no need to continue to digest. */
 		if (vec->setkey_error)
@@ -1535,7 +1533,6 @@ static void generate_random_hash_testvec(struct crypto_shash *tfm,
 	}
 
 	/* Digest */
-	desc->tfm = tfm;
 	vec->digest_error = crypto_shash_digest(desc, vec->plaintext,
 						vec->psize, (u8 *)vec->digest);
 done:
@@ -1562,6 +1559,7 @@ static int test_hash_vs_generic_impl(const char *driver,
 	const char *algname = crypto_hash_alg_common(tfm)->base.cra_name;
 	char _generic_driver[CRYPTO_MAX_ALG_NAME];
 	struct crypto_shash *generic_tfm = NULL;
+	struct shash_desc *generic_desc = NULL;
 	unsigned int i;
 	struct hash_testvec vec = { 0 };
 	char vec_name[64];
@@ -1601,6 +1599,14 @@ static int test_hash_vs_generic_impl(const char *driver,
 		goto out;
 	}
 
+	generic_desc = kzalloc(sizeof(*desc) +
+			       crypto_shash_descsize(generic_tfm), GFP_KERNEL);
+	if (!generic_desc) {
+		err = -ENOMEM;
+		goto out;
+	}
+	generic_desc->tfm = generic_tfm;
+
 	/* Check the algorithm properties for consistency. */
 
 	if (digestsize != crypto_shash_digestsize(generic_tfm)) {
@@ -1632,7 +1638,7 @@ static int test_hash_vs_generic_impl(const char *driver,
 	}
 
 	for (i = 0; i < fuzz_iterations * 8; i++) {
-		generate_random_hash_testvec(generic_tfm, &vec,
+		generate_random_hash_testvec(generic_desc, &vec,
 					     maxkeysize, maxdatasize,
 					     vec_name, sizeof(vec_name));
 		generate_random_testvec_config(cfg, cfgname, sizeof(cfgname));
@@ -1650,6 +1656,7 @@ static int test_hash_vs_generic_impl(const char *driver,
 	kfree(vec.plaintext);
 	kfree(vec.digest);
 	crypto_free_shash(generic_tfm);
+	kzfree(generic_desc);
 	return err;
 }
 #else /* !CONFIG_CRYPTO_MANAGER_EXTRA_TESTS */
-- 
2.20.0