dm crypt: separate essiv allocation from initialisation

This patch separates the construction of IV from its initialisation.
(For ESSIV it is a hash calculation based on volume key.)

Constructor code now preallocates hash tfm and salt array
and saves it in a private IV structure.

The next patch requires this to reinitialise the wiped IV
without reallocating memory when resuming a suspended device.

Cc: stable@kernel.org
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 2301d22..446153a 100644 (file)
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -71,11 +71,14 @@ struct crypt_iv_operations {
        int (*ctr)(struct crypt_config *cc, struct dm_target *ti,
                   const char *opts);
        void (*dtr)(struct crypt_config *cc);
+       int (*init)(struct crypt_config *cc);
        int (*generator)(struct crypt_config *cc, u8 *iv, sector_t sector);
 };
 
 struct iv_essiv_private {
        struct crypto_cipher *tfm;
+       struct crypto_hash *hash_tfm;
+       u8 *salt;
 };
 
 struct iv_benbi_private {
@@ -176,12 +179,38 @@ static int crypt_iv_plain_gen(struct crypt_config *cc, u8 *iv, sector_t sector)
        return 0;
 }
 
+/* Initialise ESSIV - compute salt but no local memory allocations */
+static int crypt_iv_essiv_init(struct crypt_config *cc)
+{
+       struct iv_essiv_private *essiv = &cc->iv_gen_private.essiv;
+       struct hash_desc desc;
+       struct scatterlist sg;
+       int err;
+
+       sg_init_one(&sg, cc->key, cc->key_size);
+       desc.tfm = essiv->hash_tfm;
+       desc.flags = CRYPTO_TFM_REQ_MAY_SLEEP;
+
+       err = crypto_hash_digest(&desc, &sg, cc->key_size, essiv->salt);
+       if (err)
+               return err;
+
+       return crypto_cipher_setkey(essiv->tfm, essiv->salt,
+                                   crypto_hash_digestsize(essiv->hash_tfm));
+}
+
 static void crypt_iv_essiv_dtr(struct crypt_config *cc)
 {
        struct iv_essiv_private *essiv = &cc->iv_gen_private.essiv;
 
        crypto_free_cipher(essiv->tfm);
        essiv->tfm = NULL;
+
+       crypto_free_hash(essiv->hash_tfm);
+       essiv->hash_tfm = NULL;
+
+       kzfree(essiv->salt);
+       essiv->salt = NULL;
 }
 
 static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
@@ -189,9 +218,6 @@ static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
 {
        struct crypto_cipher *essiv_tfm = NULL;
        struct crypto_hash *hash_tfm = NULL;
-       struct hash_desc desc;
-       struct scatterlist sg;
-       unsigned int saltsize;
        u8 *salt = NULL;
        int err;
 
@@ -200,7 +226,7 @@ static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
                return -EINVAL;
        }
 
-       /* Hash the cipher key with the given hash algorithm */
+       /* Allocate hash algorithm */
        hash_tfm = crypto_alloc_hash(opts, 0, CRYPTO_ALG_ASYNC);
        if (IS_ERR(hash_tfm)) {
                ti->error = "Error initializing ESSIV hash";
@@ -208,27 +234,14 @@ static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
                goto bad;
        }
 
-       saltsize = crypto_hash_digestsize(hash_tfm);
-       salt = kzalloc(saltsize, GFP_KERNEL);
+       salt = kzalloc(crypto_hash_digestsize(hash_tfm), GFP_KERNEL);
        if (!salt) {
                ti->error = "Error kmallocing salt storage in ESSIV";
                err = -ENOMEM;
                goto bad;
        }
 
-       sg_init_one(&sg, cc->key, cc->key_size);
-       desc.tfm = hash_tfm;
-       desc.flags = CRYPTO_TFM_REQ_MAY_SLEEP;
-       err = crypto_hash_digest(&desc, &sg, cc->key_size, salt);
-       crypto_free_hash(hash_tfm);
-       hash_tfm = NULL;
-
-       if (err) {
-               ti->error = "Error calculating hash in ESSIV";
-               goto bad;
-       }
-
-       /* Setup the essiv_tfm with the given salt */
+       /* Allocate essiv_tfm */
        essiv_tfm = crypto_alloc_cipher(cc->cipher, 0, CRYPTO_ALG_ASYNC);
        if (IS_ERR(essiv_tfm)) {
                ti->error = "Error allocating crypto tfm for ESSIV";
@@ -242,14 +255,11 @@ static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
                err = -EINVAL;
                goto bad;
        }
-       err = crypto_cipher_setkey(essiv_tfm, salt, saltsize);
-       if (err) {
-               ti->error = "Failed to set key for ESSIV cipher";
-               goto bad;
-       }
-       kzfree(salt);
 
+       cc->iv_gen_private.essiv.salt = salt;
        cc->iv_gen_private.essiv.tfm = essiv_tfm;
+       cc->iv_gen_private.essiv.hash_tfm = hash_tfm;
+
        return 0;
 
 bad:
@@ -257,7 +267,7 @@ bad:
                crypto_free_cipher(essiv_tfm);
        if (hash_tfm && !IS_ERR(hash_tfm))
                crypto_free_hash(hash_tfm);
-       kzfree(salt);
+       kfree(salt);
        return err;
 }
 
@@ -323,6 +333,7 @@ static struct crypt_iv_operations crypt_iv_plain_ops = {
 static struct crypt_iv_operations crypt_iv_essiv_ops = {
        .ctr       = crypt_iv_essiv_ctr,
        .dtr       = crypt_iv_essiv_dtr,
+       .init      = crypt_iv_essiv_init,
        .generator = crypt_iv_essiv_gen
 };
 
@@ -1054,6 +1065,12 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
            cc->iv_gen_ops->ctr(cc, ti, ivopts) < 0)
                goto bad_ivmode;
 
+       if (cc->iv_gen_ops && cc->iv_gen_ops->init &&
+           cc->iv_gen_ops->init(cc) < 0) {
+               ti->error = "Error initialising IV";
+               goto bad_slab_pool;
+       }
+
        cc->iv_size = crypto_ablkcipher_ivsize(tfm);
        if (cc->iv_size)
                /* at least a 64 bit sector number should fit in our buffer */