dm crypt: convert essiv from ahash to shash

In preparing to remove all stack VLA usage from the kernel[1], remove
the discouraged use of AHASH_REQUEST_ON_STACK in favor of the smaller
SHASH_DESC_ON_STACK by converting from ahash-wrapped-shash to direct
shash.  The stack allocation will be made a fixed size in a later patch
to the crypto subsystem.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 14 insertions, 17 deletions

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index c406767cb9b7..d412bd4b911c 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -99,7 +99,7 @@ struct crypt_iv_operations {
 };
 
 struct iv_essiv_private {
-        struct crypto_ahash *hash_tfm;
+        struct crypto_shash *hash_tfm;
         u8 *salt;
 };
 
@@ -327,25 +327,22 @@ static int crypt_iv_plain64be_gen(struct crypt_config *cc, u8 *iv,
 static int crypt_iv_essiv_init(struct crypt_config *cc)
 {
         struct iv_essiv_private *essiv = &cc->iv_gen_private.essiv;
-        AHASH_REQUEST_ON_STACK(req, essiv->hash_tfm);
-        struct scatterlist sg;
+        SHASH_DESC_ON_STACK(desc, essiv->hash_tfm);
         struct crypto_cipher *essiv_tfm;
         int err;
 
-        sg_init_one(&sg, cc->key, cc->key_size);
-        ahash_request_set_tfm(req, essiv->hash_tfm);
-        ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL);
-        ahash_request_set_crypt(req, &sg, essiv->salt, cc->key_size);
+        desc->tfm = essiv->hash_tfm;
+        desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
 
-        err = crypto_ahash_digest(req);
-        ahash_request_zero(req);
+        err = crypto_shash_digest(desc, cc->key, cc->key_size, essiv->salt);
+        shash_desc_zero(desc);
         if (err)
                 return err;
 
         essiv_tfm = cc->iv_private;
 
         err = crypto_cipher_setkey(essiv_tfm, essiv->salt,
-                            crypto_ahash_digestsize(essiv->hash_tfm));
+                            crypto_shash_digestsize(essiv->hash_tfm));
         if (err)
                 return err;
 
@@ -356,7 +353,7 @@ static int crypt_iv_essiv_init(struct crypt_config *cc)
 static int crypt_iv_essiv_wipe(struct crypt_config *cc)
 {
         struct iv_essiv_private *essiv = &cc->iv_gen_private.essiv;
-        unsigned salt_size = crypto_ahash_digestsize(essiv->hash_tfm);
+        unsigned salt_size = crypto_shash_digestsize(essiv->hash_tfm);
         struct crypto_cipher *essiv_tfm;
         int r, err = 0;
 
@@ -408,7 +405,7 @@ static void crypt_iv_essiv_dtr(struct crypt_config *cc)
         struct crypto_cipher *essiv_tfm;
         struct iv_essiv_private *essiv = &cc->iv_gen_private.essiv;
 
-        crypto_free_ahash(essiv->hash_tfm);
+        crypto_free_shash(essiv->hash_tfm);
         essiv->hash_tfm = NULL;
 
         kzfree(essiv->salt);
@@ -426,7 +423,7 @@ static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
                               const char *opts)
 {
         struct crypto_cipher *essiv_tfm = NULL;
-        struct crypto_ahash *hash_tfm = NULL;
+        struct crypto_shash *hash_tfm = NULL;
         u8 *salt = NULL;
         int err;
 
@@ -436,14 +433,14 @@ static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
         }
 
         /* Allocate hash algorithm */
-        hash_tfm = crypto_alloc_ahash(opts, 0, CRYPTO_ALG_ASYNC);
+        hash_tfm = crypto_alloc_shash(opts, 0, 0);
         if (IS_ERR(hash_tfm)) {
                 ti->error = "Error initializing ESSIV hash";
                 err = PTR_ERR(hash_tfm);
                 goto bad;
         }
 
-        salt = kzalloc(crypto_ahash_digestsize(hash_tfm), GFP_KERNEL);
+        salt = kzalloc(crypto_shash_digestsize(hash_tfm), GFP_KERNEL);
         if (!salt) {
                 ti->error = "Error kmallocing salt storage in ESSIV";
                 err = -ENOMEM;
@@ -454,7 +451,7 @@ static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
         cc->iv_gen_private.essiv.hash_tfm = hash_tfm;
 
         essiv_tfm = alloc_essiv_cipher(cc, ti, salt,
-                                       crypto_ahash_digestsize(hash_tfm));
+                                       crypto_shash_digestsize(hash_tfm));
         if (IS_ERR(essiv_tfm)) {
                 crypt_iv_essiv_dtr(cc);
                 return PTR_ERR(essiv_tfm);
@@ -465,7 +462,7 @@ static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
 
 bad:
         if (hash_tfm && !IS_ERR(hash_tfm))
-                crypto_free_ahash(hash_tfm);
+                crypto_free_shash(hash_tfm);
         kfree(salt);
         return err;
 }