crypto: testmgr - skip crc32c context test for ahash algorithms

Instantiating "cryptd(crc32c)" causes a crypto self-test failure because
the crypto_alloc_shash() in alg_test_crc32c() fails.  This is because
cryptd(crc32c) is an ahash algorithm, not a shash algorithm; so it can
only be accessed through the ahash API, unlike shash algorithms which
can be accessed through both the ahash and shash APIs.

As the test is testing the shash descriptor format which is only
applicable to shash algorithms, skip it for ahash algorithms.

(Note that it's still important to fix crypto self-test failures even
 for weird algorithm instantiations like cryptd(crc32c) that no one
 would really use; in fips_enabled mode unprivileged users can use them
 to panic the kernel, and also they prevent treating a crypto self-test
 failure as a bug when fuzzing the kernel.)

Fixes: 8e3ee85e ("crypto: crc32c - Test descriptor context format")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/testmgr.c

@@ -1909,14 +1909,21 @@ static int alg_test_crc32c(const struct alg_test_desc *desc,
 
 	err = alg_test_hash(desc, driver, type, mask);
 	if (err)
-		goto out;
+		return err;
 
 	tfm = crypto_alloc_shash(driver, type, mask);
 	if (IS_ERR(tfm)) {
+		if (PTR_ERR(tfm) == -ENOENT) {
+			/*
+			 * This crc32c implementation is only available through
+			 * ahash API, not the shash API, so the remaining part
+			 * of the test is not applicable to it.
+			 */
+			return 0;
+		}
 		printk(KERN_ERR "alg: crc32c: Failed to load transform for %s: "
 		       "%ld\n", driver, PTR_ERR(tfm));
-		err = PTR_ERR(tfm);
-		goto out;
+		return PTR_ERR(tfm);
 	}
 
 	do {
@@ -1943,7 +1950,6 @@ static int alg_test_crc32c(const struct alg_test_desc *desc,
 
 	crypto_free_shash(tfm);
 
-out:
 	return err;
 }