[PATCH v2 2/2] crypto: ctr - Propagate NEED_FALLBACK bit

From: Marcelo Henrique Cerri
Date: Mon Feb 27 2017 - 07:42:44 EST


When requesting a fallback algorithm, we should propagate the
NEED_FALLBACK bit when search for the underlying algorithm.

This will prevents drivers from allocating unnecessary fallbacks that
are never called. For instance, currently the vmx-crypto driver will use
the following chain of calls when calling the fallback implementation:

p8_aes_ctr -> ctr(p8_aes) -> aes-generic

However p8_aes will always delegate its calls to aes-generic. With this
patch, p8_aes_ctr will be able to use ctr(aes-generic) directly as its
fallback. The same applies to aes_s390.

Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri@xxxxxxxxxxxxx>
---
crypto/ctr.c | 23 ++++++++++++++++++-----
1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/crypto/ctr.c b/crypto/ctr.c
index a4f4a89..477d922 100644
--- a/crypto/ctr.c
+++ b/crypto/ctr.c
@@ -181,15 +181,24 @@ static void crypto_ctr_exit_tfm(struct crypto_tfm *tfm)
static struct crypto_instance *crypto_ctr_alloc(struct rtattr **tb)
{
struct crypto_instance *inst;
+ struct crypto_attr_type *algt;
struct crypto_alg *alg;
+ u32 mask;
int err;

err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
if (err)
return ERR_PTR(err);

- alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
- CRYPTO_ALG_TYPE_MASK);
+ algt = crypto_get_attr_type(tb);
+ if (IS_ERR(algt))
+ return ERR_CAST(algt);
+
+ mask = CRYPTO_ALG_TYPE_MASK |
+ crypto_requires_off(algt->type, algt->mask,
+ CRYPTO_ALG_NEED_FALLBACK);
+
+ alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER, mask);
if (IS_ERR(alg))
return ERR_CAST(alg);

@@ -350,6 +359,8 @@ static int crypto_rfc3686_create(struct crypto_template *tmpl,
struct skcipher_alg *alg;
struct crypto_skcipher_spawn *spawn;
const char *cipher_name;
+ u32 mask;
+
int err;

algt = crypto_get_attr_type(tb);
@@ -367,12 +378,14 @@ static int crypto_rfc3686_create(struct crypto_template *tmpl,
if (!inst)
return -ENOMEM;

+ mask = crypto_requires_sync(algt->type, algt->mask) |
+ crypto_requires_off(algt->type, algt->mask,
+ CRYPTO_ALG_NEED_FALLBACK);
+
spawn = skcipher_instance_ctx(inst);

crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
- err = crypto_grab_skcipher(spawn, cipher_name, 0,
- crypto_requires_sync(algt->type,
- algt->mask));
+ err = crypto_grab_skcipher(spawn, cipher_name, 0, mask);
if (err)
goto err_free_inst;

--
2.7.4