[PATCH v4 3/6] md: dm-crypt: infer ESSIV block cipher from cipher string directly

[Ard Biesheuvel <ard.biesheuvel@xxxxxxx>]

From: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>

Instead of allocating a crypto skcipher tfm 'foo' and attempting to
infer the encapsulated block cipher from the driver's 'name' field,
directly parse the string that we used to allocated the tfm. These
are always identical (unless the allocation failed, in which case
we bail anyway), but using the string allows us to use it in the
allocation, which is something we will need when switching to the
'essiv' crypto API template.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
---
 drivers/md/dm-crypt.c | 35 +++++++++-----------
 1 file changed, 15 insertions(+), 20 deletions(-)

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 1b16d34bb785..f001f1104cb5 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -2321,25 +2321,17 @@ static int crypt_ctr_ivmode(struct dm_target *ti, const char *ivmode)
  * The cc->cipher is currently used only in ESSIV.
  * This should be probably done by crypto-api calls (once available...)
  */
-static int crypt_ctr_blkdev_cipher(struct crypt_config *cc)
+static int crypt_ctr_blkdev_cipher(struct crypt_config *cc, char *alg_name)
 {
-	const char *alg_name = NULL;
 	char *start, *end;
 
 	if (crypt_integrity_aead(cc)) {
-		alg_name = crypto_tfm_alg_name(crypto_aead_tfm(any_tfm_aead(cc)));
-		if (!alg_name)
-			return -EINVAL;
 		if (crypt_integrity_hmac(cc)) {
 			alg_name = strchr(alg_name, ',');
 			if (!alg_name)
 				return -EINVAL;
 		}
 		alg_name++;
-	} else {
-		alg_name = crypto_tfm_alg_name(crypto_skcipher_tfm(any_tfm(cc)));
-		if (!alg_name)
-			return -EINVAL;
 	}
 
 	start = strchr(alg_name, '(');
@@ -2434,6 +2426,20 @@ static int crypt_ctr_cipher_new(struct dm_target *ti, char *cipher_in, char *key
 	if (*ivmode && !strcmp(*ivmode, "lmk"))
 		cc->tfms_count = 64;
 
+	if (crypt_integrity_aead(cc)) {
+		ret = crypt_ctr_auth_cipher(cc, cipher_api);
+		if (ret < 0) {
+			ti->error = "Invalid AEAD cipher spec";
+			return -ENOMEM;
+	       }
+	}
+
+	ret = crypt_ctr_blkdev_cipher(cc, cipher_api);
+	if (ret < 0) {
+		ti->error = "Cannot allocate cipher string";
+		return -ENOMEM;
+	}
+
 	cc->key_parts = cc->tfms_count;
 
 	/* Allocate cipher */
@@ -2445,21 +2451,10 @@ static int crypt_ctr_cipher_new(struct dm_target *ti, char *cipher_in, char *key
 
 	/* Alloc AEAD, can be used only in new format. */
 	if (crypt_integrity_aead(cc)) {
-		ret = crypt_ctr_auth_cipher(cc, cipher_api);
-		if (ret < 0) {
-			ti->error = "Invalid AEAD cipher spec";
-			return -ENOMEM;
-		}
 		cc->iv_size = crypto_aead_ivsize(any_tfm_aead(cc));
 	} else
 		cc->iv_size = crypto_skcipher_ivsize(any_tfm(cc));
 
-	ret = crypt_ctr_blkdev_cipher(cc);
-	if (ret < 0) {
-		ti->error = "Cannot allocate cipher string";
-		return -ENOMEM;
-	}
-
 	return 0;
 }
 
-- 
2.17.1