The two thing that should be handled are cipher and ivgen. For ivgen
the solution is just mutex, as iv calculations should not be long in
comparison with encryption/decryption. And for cipher let's just keep
per-thread ciphers.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 crypto/blockpriv.h        |  16 ++++-
 include/crypto/block.h    |   2 +
 block/crypto.c            |   1 +
 block/qcow.c              |   2 +-
 block/qcow2.c             |   4 +-
 crypto/block-luks.c       |  22 +++---
 crypto/block-qcow.c       |  20 +++---
 crypto/block.c            | 146 +++++++++++++++++++++++++++++++++-----
 tests/test-crypto-block.c |   3 +
 9 files changed, 172 insertions(+), 44 deletions(-)

diff --git a/crypto/blockpriv.h b/crypto/blockpriv.h
index 438c08bec2..5438e822fd 100644
--- a/crypto/blockpriv.h
+++ b/crypto/blockpriv.h
@@ -22,6 +22,7 @@
 #define QCRYPTO_BLOCKPRIV_H
 
 #include "crypto/block.h"
+#include "qemu/thread.h"
 
 typedef struct QCryptoBlockDriver QCryptoBlockDriver;
 
@@ -31,8 +32,12 @@ struct QCryptoBlock {
     const QCryptoBlockDriver *driver;
     void *opaque;
 
-    QCryptoCipher *cipher;
+    QCryptoCipher **ciphers;
+    size_t n_ciphers;
+    size_t n_free_ciphers;
     QCryptoIVGen *ivgen;
+    QemuMutex mutex;
+
     QCryptoHashAlgorithm kdfhash;
     size_t niv;
     uint64_t payload_offset; /* In bytes */
@@ -46,6 +51,7 @@ struct QCryptoBlockDriver {
                 QCryptoBlockReadFunc readfunc,
                 void *opaque,
                 unsigned int flags,
+                size_t n_threads,
                 Error **errp);
 
     int (*create)(QCryptoBlock *block,
@@ -110,4 +116,12 @@ int qcrypto_block_encrypt_helper(QCryptoBlock *block,
                                  size_t len,
                                  Error **errp);
 
+int qcrypto_block_init_cipher(QCryptoBlock *block,
+                              QCryptoCipherAlgorithm alg,
+                              QCryptoCipherMode mode,
+                              const uint8_t *key, size_t nkey,
+                              size_t n_threads, Error **errp);
+
+void qcrypto_block_free_cipher(QCryptoBlock *block);
+
 #endif /* QCRYPTO_BLOCKPRIV_H */
diff --git a/include/crypto/block.h b/include/crypto/block.h
index cd18f46d56..e729d5bd66 100644
--- a/include/crypto/block.h
+++ b/include/crypto/block.h
@@ -75,6 +75,7 @@ typedef enum {
  * @readfunc: callback for reading data from the volume
  * @opaque: data to pass to @readfunc
  * @flags: bitmask of QCryptoBlockOpenFlags values
+ * @n_threads: allow concurrent I/O from up to @n_threads threads
  * @errp: pointer to a NULL-initialized error object
  *
  * Create a new block encryption object for an existing
@@ -107,6 +108,7 @@ QCryptoBlock *qcrypto_block_open(QCryptoBlockOpenOptions *options,
                                  QCryptoBlockReadFunc readfunc,
                                  void *opaque,
                                  unsigned int flags,
+                                 size_t n_threads,
                                  Error **errp);
 
 /**
diff --git a/block/crypto.c b/block/crypto.c
index 33ee01bebd..f0a5f6b987 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -229,6 +229,7 @@ static int block_crypto_open_generic(QCryptoBlockFormat format,
                                        block_crypto_read_func,
                                        bs,
                                        cflags,
+                                       1,
                                        errp);
 
     if (!crypto->block) {
diff --git a/block/qcow.c b/block/qcow.c
index 4518cb4c35..0a235bf393 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -213,7 +213,7 @@ static int qcow_open(BlockDriverState *bs, QDict *options, int flags,
                 cflags |= QCRYPTO_BLOCK_OPEN_NO_IO;
             }
             s->crypto = qcrypto_block_open(crypto_opts, "encrypt.",
-                                           NULL, NULL, cflags, errp);
+                                           NULL, NULL, cflags, 1, errp);
             if (!s->crypto) {
                 ret = -EINVAL;
                 goto fail;
diff --git a/block/qcow2.c b/block/qcow2.c
index 991d6ac91b..bc8868c36a 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -294,7 +294,7 @@ static int qcow2_read_extensions(BlockDriverState *bs, uint64_t start_offset,
             }
             s->crypto = qcrypto_block_open(s->crypto_opts, "encrypt.",
                                            qcow2_crypto_hdr_read_func,
-                                           bs, cflags, errp);
+                                           bs, cflags, 1, errp);
             if (!s->crypto) {
                 return -EINVAL;
             }
@@ -1445,7 +1445,7 @@ static int coroutine_fn qcow2_do_open(BlockDriverState *bs, QDict *options,
                 cflags |= QCRYPTO_BLOCK_OPEN_NO_IO;
             }
             s->crypto = qcrypto_block_open(s->crypto_opts, "encrypt.",
-                                           NULL, NULL, cflags, errp);
+                                           NULL, NULL, cflags, 1, errp);
             if (!s->crypto) {
                 ret = -EINVAL;
                 goto fail;
diff --git a/crypto/block-luks.c b/crypto/block-luks.c
index e486e7ee94..6bac79c3ab 100644
--- a/crypto/block-luks.c
+++ b/crypto/block-luks.c
@@ -636,6 +636,7 @@ qcrypto_block_luks_open(QCryptoBlock *block,
                         QCryptoBlockReadFunc readfunc,
                         void *opaque,
                         unsigned int flags,
+                        size_t n_threads,
                         Error **errp)
 {
     QCryptoBlockLUKS *luks;
@@ -836,11 +837,10 @@ qcrypto_block_luks_open(QCryptoBlock *block,
             goto fail;
         }
 
-        block->cipher = qcrypto_cipher_new(cipheralg,
-                                           ciphermode,
-                                           masterkey, masterkeylen,
-                                           errp);
-        if (!block->cipher) {
+        ret = qcrypto_block_init_cipher(block, cipheralg, ciphermode,
+                                        masterkey, masterkeylen, n_threads,
+                                        errp);
+        if (ret < 0) {
             ret = -ENOTSUP;
             goto fail;
         }
@@ -863,7 +863,7 @@ qcrypto_block_luks_open(QCryptoBlock *block,
 
  fail:
     g_free(masterkey);
-    qcrypto_cipher_free(block->cipher);
+    qcrypto_block_free_cipher(block);
     qcrypto_ivgen_free(block->ivgen);
     g_free(luks);
     g_free(password);
@@ -1030,11 +1030,9 @@ qcrypto_block_luks_create(QCryptoBlock *block,
 
 
     /* Setup the block device payload encryption objects */
-    block->cipher = qcrypto_cipher_new(luks_opts.cipher_alg,
-                                       luks_opts.cipher_mode,
-                                       masterkey, luks->header.key_bytes,
-                                       errp);
-    if (!block->cipher) {
+    if (qcrypto_block_init_cipher(block, luks_opts.cipher_alg,
+                                  luks_opts.cipher_mode, masterkey,
+                                  luks->header.key_bytes, 1, errp) < 0) {
         goto error;
     }
 
@@ -1341,7 +1339,7 @@ qcrypto_block_luks_create(QCryptoBlock *block,
     qcrypto_ivgen_free(ivgen);
     qcrypto_cipher_free(cipher);
 
-    qcrypto_cipher_free(block->cipher);
+    qcrypto_block_free_cipher(block);
     qcrypto_ivgen_free(block->ivgen);
 
     g_free(luks);
diff --git a/crypto/block-qcow.c b/crypto/block-qcow.c
index 36bf5f09b7..cefb3b2a7b 100644
--- a/crypto/block-qcow.c
+++ b/crypto/block-qcow.c
@@ -44,6 +44,7 @@ qcrypto_block_qcow_has_format(const uint8_t *buf G_GNUC_UNUSED,
 static int
 qcrypto_block_qcow_init(QCryptoBlock *block,
                         const char *keysecret,
+                        size_t n_threads,
                         Error **errp)
 {
     char *password;
@@ -71,11 +72,11 @@ qcrypto_block_qcow_init(QCryptoBlock *block,
         goto fail;
     }
 
-    block->cipher = qcrypto_cipher_new(QCRYPTO_CIPHER_ALG_AES_128,
-                                       QCRYPTO_CIPHER_MODE_CBC,
-                                       keybuf, G_N_ELEMENTS(keybuf),
-                                       errp);
-    if (!block->cipher) {
+    ret = qcrypto_block_init_cipher(block, QCRYPTO_CIPHER_ALG_AES_128,
+                                    QCRYPTO_CIPHER_MODE_CBC,
+                                    keybuf, G_N_ELEMENTS(keybuf),
+                                    n_threads, errp);
+    if (ret < 0) {
         ret = -ENOTSUP;
         goto fail;
     }
@@ -86,7 +87,7 @@ qcrypto_block_qcow_init(QCryptoBlock *block,
     return 0;
 
  fail:
-    qcrypto_cipher_free(block->cipher);
+    qcrypto_block_free_cipher(block);
     qcrypto_ivgen_free(block->ivgen);
     return ret;
 }
@@ -99,6 +100,7 @@ qcrypto_block_qcow_open(QCryptoBlock *block,
                         QCryptoBlockReadFunc readfunc G_GNUC_UNUSED,
                         void *opaque G_GNUC_UNUSED,
                         unsigned int flags,
+                        size_t n_threads,
                         Error **errp)
 {
     if (flags & QCRYPTO_BLOCK_OPEN_NO_IO) {
@@ -112,8 +114,8 @@ qcrypto_block_qcow_open(QCryptoBlock *block,
                        optprefix ? optprefix : "");
             return -1;
         }
-        return qcrypto_block_qcow_init(block,
-                                       options->u.qcow.key_secret, errp);
+        return qcrypto_block_qcow_init(block, options->u.qcow.key_secret,
+                                       n_threads, errp);
     }
 }
 
@@ -133,7 +135,7 @@ qcrypto_block_qcow_create(QCryptoBlock *block,
         return -1;
     }
     /* QCow2 has no special header, since everything is hardwired */
-    return qcrypto_block_qcow_init(block, options->u.qcow.key_secret, errp);
+    return qcrypto_block_qcow_init(block, options->u.qcow.key_secret, 1, errp);
 }
 
 
diff --git a/crypto/block.c b/crypto/block.c
index 3fe3de2ef8..d70d401f87 100644
--- a/crypto/block.c
+++ b/crypto/block.c
@@ -52,6 +52,7 @@ QCryptoBlock *qcrypto_block_open(QCryptoBlockOpenOptions *options,
                                  QCryptoBlockReadFunc readfunc,
                                  void *opaque,
                                  unsigned int flags,
+                                 size_t n_threads,
                                  Error **errp)
 {
     QCryptoBlock *block = g_new0(QCryptoBlock, 1);
@@ -69,11 +70,14 @@ QCryptoBlock *qcrypto_block_open(QCryptoBlockOpenOptions *options,
     block->driver = qcrypto_block_drivers[options->format];
 
     if (block->driver->open(block, options, optprefix,
-                            readfunc, opaque, flags, errp) < 0) {
+                            readfunc, opaque, flags, n_threads, errp) < 0)
+    {
         g_free(block);
         return NULL;
     }
 
+    qemu_mutex_init(&block->mutex);
+
     return block;
 }
 
@@ -105,6 +109,8 @@ QCryptoBlock *qcrypto_block_create(QCryptoBlockCreateOptions *options,
         return NULL;
     }
 
+    qemu_mutex_init(&block->mutex);
+
     return block;
 }
 
@@ -148,12 +154,97 @@ int qcrypto_block_encrypt(QCryptoBlock *block,
 
 QCryptoCipher *qcrypto_block_get_cipher(QCryptoBlock *block)
 {
-    return block->cipher;
+    /* Ciphers should be accessed through pop/push method to be thread-safe.
+     * Better, they should not be accessed externally at all (note, that
+     * pop/push are static functions)
+     * This function is used only in test with one thread (it's safe to skip
+     * pop/push interface), so it's enough to assert it here:
+     */
+    assert(block->n_ciphers <= 1);
+    return block->ciphers ? block->ciphers[0] : NULL;
+}
+
+
+static QCryptoCipher *qcrypto_block_pop_cipher(QCryptoBlock *block)
+{
+    QCryptoCipher *cipher;
+
+    qemu_mutex_lock(&block->mutex);
+
+    assert(block->n_free_ciphers > 0);
+    block->n_free_ciphers--;
+    cipher = block->ciphers[block->n_free_ciphers];
+
+    qemu_mutex_unlock(&block->mutex);
+
+    return cipher;
+}
+
+
+static void qcrypto_block_push_cipher(QCryptoBlock *block,
+                                      QCryptoCipher *cipher)
+{
+    qemu_mutex_lock(&block->mutex);
+
+    assert(block->n_free_ciphers < block->n_ciphers);
+    block->ciphers[block->n_free_ciphers] = cipher;
+    block->n_free_ciphers++;
+
+    qemu_mutex_unlock(&block->mutex);
+}
+
+
+int qcrypto_block_init_cipher(QCryptoBlock *block,
+                              QCryptoCipherAlgorithm alg,
+                              QCryptoCipherMode mode,
+                              const uint8_t *key, size_t nkey,
+                              size_t n_threads, Error **errp)
+{
+    size_t i;
+
+    assert(!block->ciphers && !block->n_ciphers && !block->n_free_ciphers);
+
+    block->ciphers = g_new0(QCryptoCipher *, n_threads);
+
+    for (i = 0; i < n_threads; i++) {
+        block->ciphers[i] = qcrypto_cipher_new(alg, mode, key, nkey, errp);
+        if (!block->ciphers[i]) {
+            qcrypto_block_free_cipher(block);
+            return -1;
+        }
+        block->n_ciphers++;
+        block->n_free_ciphers++;
+    }
+
+    return 0;
 }
 
 
+void qcrypto_block_free_cipher(QCryptoBlock *block)
+{
+    size_t i;
+
+    if (!block->ciphers) {
+        return;
+    }
+
+    assert(block->n_ciphers == block->n_free_ciphers);
+
+    for (i = 0; i < block->n_ciphers; i++) {
+        qcrypto_cipher_free(block->ciphers[i]);
+    }
+
+    g_free(block->ciphers);
+    block->ciphers = NULL;
+    block->n_ciphers = block->n_free_ciphers = 0;
+}
+
 QCryptoIVGen *qcrypto_block_get_ivgen(QCryptoBlock *block)
 {
+    /* ivgen should be accessed under mutex. However, this function is used only
+     * in test with one thread, so it's enough to assert it here:
+     */
+    assert(block->n_ciphers <= 1);
     return block->ivgen;
 }
 
@@ -184,8 +275,9 @@ void qcrypto_block_free(QCryptoBlock *block)
 
     block->driver->cleanup(block);
 
-    qcrypto_cipher_free(block->cipher);
+    qcrypto_block_free_cipher(block);
     qcrypto_ivgen_free(block->ivgen);
+    qemu_mutex_destroy(&block->mutex);
     g_free(block);
 }
 
@@ -199,6 +291,7 @@ typedef int (*QCryptoCipherEncDecFunc)(QCryptoCipher *cipher,
 static int do_qcrypto_block_cipher_encdec(QCryptoCipher *cipher,
                                           size_t niv,
                                           QCryptoIVGen *ivgen,
+                                          QemuMutex *ivgen_mutex,
                                           int sectorsize,
                                           uint64_t offset,
                                           uint8_t *buf,
@@ -218,10 +311,15 @@ static int do_qcrypto_block_cipher_encdec(QCryptoCipher *cipher,
     while (len > 0) {
         size_t nbytes;
         if (niv) {
-            if (qcrypto_ivgen_calculate(ivgen,
-                                        startsector,
-                                        iv, niv,
-                                        errp) < 0) {
+            if (ivgen_mutex) {
+                qemu_mutex_lock(ivgen_mutex);
+            }
+            ret = qcrypto_ivgen_calculate(ivgen, startsector, iv, niv, errp);
+            if (ivgen_mutex) {
+                qemu_mutex_unlock(ivgen_mutex);
+            }
+
+            if (ret < 0) {
                 goto cleanup;
             }
 
@@ -258,7 +356,7 @@ int qcrypto_block_cipher_decrypt_helper(QCryptoCipher *cipher,
                                         size_t len,
                                         Error **errp)
 {
-    return do_qcrypto_block_cipher_encdec(cipher, niv, ivgen, sectorsize,
+    return do_qcrypto_block_cipher_encdec(cipher, niv, ivgen, NULL, sectorsize,
                                           offset, buf, len,
                                           qcrypto_cipher_decrypt, errp);
 }
@@ -273,12 +371,11 @@ int qcrypto_block_cipher_encrypt_helper(QCryptoCipher *cipher,
                                         size_t len,
                                         Error **errp)
 {
-    return do_qcrypto_block_cipher_encdec(cipher, niv, ivgen, sectorsize,
+    return do_qcrypto_block_cipher_encdec(cipher, niv, ivgen, NULL, sectorsize,
                                           offset, buf, len,
                                           qcrypto_cipher_encrypt, errp);
 }
 
-
 int qcrypto_block_decrypt_helper(QCryptoBlock *block,
                                  int sectorsize,
                                  uint64_t offset,
@@ -286,12 +383,17 @@ int qcrypto_block_decrypt_helper(QCryptoBlock *block,
                                  size_t len,
                                  Error **errp)
 {
-    return do_qcrypto_block_cipher_encdec(block->cipher, block->niv,
-                                          block->ivgen,
-                                          sectorsize, offset, buf, len,
-                                          qcrypto_cipher_decrypt, errp);
-}
+    int ret;
+    QCryptoCipher *cipher = qcrypto_block_pop_cipher(block);
 
+    ret = do_qcrypto_block_cipher_encdec(cipher, block->niv, block->ivgen,
+                                         &block->mutex, sectorsize, offset, buf,
+                                         len, qcrypto_cipher_decrypt, errp);
+
+    qcrypto_block_push_cipher(block, cipher);
+
+    return ret;
+}
 
 int qcrypto_block_encrypt_helper(QCryptoBlock *block,
                                  int sectorsize,
@@ -300,8 +402,14 @@ int qcrypto_block_encrypt_helper(QCryptoBlock *block,
                                  size_t len,
                                  Error **errp)
 {
-    return do_qcrypto_block_cipher_encdec(block->cipher, block->niv,
-                                          block->ivgen,
-                                          sectorsize, offset, buf, len,
-                                          qcrypto_cipher_encrypt, errp);
+    int ret;
+    QCryptoCipher *cipher = qcrypto_block_pop_cipher(block);
+
+    ret = do_qcrypto_block_cipher_encdec(cipher, block->niv, block->ivgen,
+                                         &block->mutex, sectorsize, offset, buf,
+                                         len, qcrypto_cipher_encrypt, errp);
+
+    qcrypto_block_push_cipher(block, cipher);
+
+    return ret;
 }
diff --git a/tests/test-crypto-block.c b/tests/test-crypto-block.c
index fae4ffc453..d309d044ef 100644
--- a/tests/test-crypto-block.c
+++ b/tests/test-crypto-block.c
@@ -305,6 +305,7 @@ static void test_block(gconstpointer opaque)
                              test_block_read_func,
                              &header,
                              0,
+                             1,
                              NULL);
     g_assert(blk == NULL);
 
@@ -313,6 +314,7 @@ static void test_block(gconstpointer opaque)
                              test_block_read_func,
                              &header,
                              QCRYPTO_BLOCK_OPEN_NO_IO,
+                             1,
                              &error_abort);
 
     g_assert(qcrypto_block_get_cipher(blk) == NULL);
@@ -327,6 +329,7 @@ static void test_block(gconstpointer opaque)
                              test_block_read_func,
                              &header,
                              0,
+                             1,
                              &error_abort);
     g_assert(blk);
 
-- 
2.18.0

On Fri 07 Dec 2018 05:13:51 PM CET, Vladimir Sementsov-Ogievskiy wrote:
> @@ -148,12 +154,97 @@ int qcrypto_block_encrypt(QCryptoBlock *block,
>  
>  QCryptoCipher *qcrypto_block_get_cipher(QCryptoBlock *block)
>  {
> -    return block->cipher;
> +    /* Ciphers should be accessed through pop/push method to be thread-safe.
> +     * Better, they should not be accessed externally at all (note, that
> +     * pop/push are static functions)
> +     * This function is used only in test with one thread (it's safe to skip
> +     * pop/push interface), so it's enough to assert it here:
> +     */
> +    assert(block->n_ciphers <= 1);
> +    return block->ciphers ? block->ciphers[0] : NULL;

If this is only supposed to be called in test mode I think you can also
assert that g_test_initialized() is true.

And the same with qcrypto_block_get_ivgen() later in this patch.

> +int qcrypto_block_init_cipher(QCryptoBlock *block,
> +                              QCryptoCipherAlgorithm alg,
> +                              QCryptoCipherMode mode,
> +                              const uint8_t *key, size_t nkey,
> +                              size_t n_threads, Error **errp)
> +{
> +    size_t i;
> +
> +    assert(!block->ciphers && !block->n_ciphers && !block->n_free_ciphers);
> +
> +    block->ciphers = g_new0(QCryptoCipher *, n_threads);

You can use g_new() instead of g_new0() because you're anyway
overwriting all elements of the array.

But these are minor nits, the patchs looks good to me else.

Reviewed-by: Alberto Garcia <berto@igalia.com>

Berto

On Mon, Dec 10, 2018 at 03:06:59PM +0100, Alberto Garcia wrote:
> On Fri 07 Dec 2018 05:13:51 PM CET, Vladimir Sementsov-Ogievskiy wrote:
> > @@ -148,12 +154,97 @@ int qcrypto_block_encrypt(QCryptoBlock *block,
> >  
> >  QCryptoCipher *qcrypto_block_get_cipher(QCryptoBlock *block)
> >  {
> > -    return block->cipher;
> > +    /* Ciphers should be accessed through pop/push method to be thread-safe.
> > +     * Better, they should not be accessed externally at all (note, that
> > +     * pop/push are static functions)
> > +     * This function is used only in test with one thread (it's safe to skip
> > +     * pop/push interface), so it's enough to assert it here:
> > +     */
> > +    assert(block->n_ciphers <= 1);
> > +    return block->ciphers ? block->ciphers[0] : NULL;
> 
> If this is only supposed to be called in test mode I think you can also
> assert that g_test_initialized() is true.
> 
> And the same with qcrypto_block_get_ivgen() later in this patch.

I consider these APIs as being valid for use anywhere - it just
happens it is only used in the tests right now. So I think it is
ok to assert on n_cipers here.

> > +int qcrypto_block_init_cipher(QCryptoBlock *block,
> > +                              QCryptoCipherAlgorithm alg,
> > +                              QCryptoCipherMode mode,
> > +                              const uint8_t *key, size_t nkey,
> > +                              size_t n_threads, Error **errp)
> > +{
> > +    size_t i;
> > +
> > +    assert(!block->ciphers && !block->n_ciphers && !block->n_free_ciphers);
> > +
> > +    block->ciphers = g_new0(QCryptoCipher *, n_threads);
> 
> You can use g_new() instead of g_new0() because you're anyway
> overwriting all elements of the array.

I'd rather have it initialized to zero upfront, so if creating any
cipher in the array fails, we don't have uninitialized array elements
during later cleanup code.

> But these are minor nits, the patchs looks good to me else.
> 
> Reviewed-by: Alberto Garcia <berto@igalia.com>

Regards,
Daniel
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On Mon 10 Dec 2018 03:52:03 PM CET, Daniel P. Berrangé wrote:
>> > +int qcrypto_block_init_cipher(QCryptoBlock *block,
>> > +                              QCryptoCipherAlgorithm alg,
>> > +                              QCryptoCipherMode mode,
>> > +                              const uint8_t *key, size_t nkey,
>> > +                              size_t n_threads, Error **errp)
>> > +{
>> > +    size_t i;
>> > +
>> > +    assert(!block->ciphers && !block->n_ciphers && !block->n_free_ciphers);
>> > +
>> > +    block->ciphers = g_new0(QCryptoCipher *, n_threads);
>> 
>> You can use g_new() instead of g_new0() because you're anyway
>> overwriting all elements of the array.
>
> I'd rather have it initialized to zero upfront, so if creating any
> cipher in the array fails, we don't have uninitialized array elements
> during later cleanup code.

But it is the value of block->n_ciphers that determines the size of the
array, and that is only incremented after each successful iteration:

  for (i = 0; i < n_threads; i++) {
      block->ciphers[i] = qcrypto_cipher_new(alg, mode, key, nkey, errp);
      /* ... error handling ... */
      block->n_ciphers++;
      block->n_free_ciphers++;
  }

In other words, the cleanup code won't touch uninitialized elements
because it cannot even tell the difference between an index that points
to an uninitialized element of the array and an index that points beyond
the allocated memory.

Berto

On Mon, Dec 10, 2018 at 04:09:31PM +0100, Alberto Garcia wrote:
> On Mon 10 Dec 2018 03:52:03 PM CET, Daniel P. Berrangé wrote:
> >> > +int qcrypto_block_init_cipher(QCryptoBlock *block,
> >> > +                              QCryptoCipherAlgorithm alg,
> >> > +                              QCryptoCipherMode mode,
> >> > +                              const uint8_t *key, size_t nkey,
> >> > +                              size_t n_threads, Error **errp)
> >> > +{
> >> > +    size_t i;
> >> > +
> >> > +    assert(!block->ciphers && !block->n_ciphers && !block->n_free_ciphers);
> >> > +
> >> > +    block->ciphers = g_new0(QCryptoCipher *, n_threads);
> >> 
> >> You can use g_new() instead of g_new0() because you're anyway
> >> overwriting all elements of the array.
> >
> > I'd rather have it initialized to zero upfront, so if creating any
> > cipher in the array fails, we don't have uninitialized array elements
> > during later cleanup code.
> 
> But it is the value of block->n_ciphers that determines the size of the
> array, and that is only incremented after each successful iteration:
> 
>   for (i = 0; i < n_threads; i++) {
>       block->ciphers[i] = qcrypto_cipher_new(alg, mode, key, nkey, errp);
>       /* ... error handling ... */
>       block->n_ciphers++;
>       block->n_free_ciphers++;
>   }
> 
> In other words, the cleanup code won't touch uninitialized elements
> because it cannot even tell the difference between an index that points
> to an uninitialized element of the array and an index that points beyond
> the allocated memory.

.../correctly written/ cleanup code won't touch uninitialized elements...

I prefer to see the code be hardened against mistakes and so would always
zero-initialize everything unless there's compelling performance reason
not to in certain specific places.

Regards,
Daniel
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On Mon 10 Dec 2018 04:16:48 PM CET, Daniel P. Berrangé wrote:
>> In other words, the cleanup code won't touch uninitialized elements
>> because it cannot even tell the difference between an index that
>> points to an uninitialized element of the array and an index that
>> points beyond the allocated memory.
>
> .../correctly written/ cleanup code won't touch uninitialized elements...
>
> I prefer to see the code be hardened against mistakes and so would
> always zero-initialize everything unless there's compelling
> performance reason not to in certain specific places.

Ok, sounds reasonable.

Berto