virtio-crypto: fix possible integer and heap overflow

Because the 'size_t' type is 4 bytes in 32-bit platform, which
is the same with 'int'. It's easy to make 'max_len' to zero when
integer overflow and then cause heap overflow if 'max_len' is zero.

Using uint_64 instead of size_t to avoid the integer overflow.

Cc: qemu-stable@nongnu.org
Reported-by: Li Qiang <liqiang6-s@360.cn>
Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Tested-by: Li Qiang <liqiang6-s@360.cn>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/virtio/virtio-crypto.c

@@ -416,7 +416,7 @@ virtio_crypto_sym_op_helper(VirtIODevice *vdev,
     uint32_t hash_start_src_offset = 0, len_to_hash = 0;
     uint32_t cipher_start_src_offset = 0, len_to_cipher = 0;
 
-    size_t max_len, curr_size = 0;
+    uint64_t max_len, curr_size = 0;
     size_t s;
 
     /* Plain cipher */
@@ -441,7 +441,7 @@ virtio_crypto_sym_op_helper(VirtIODevice *vdev,
         return NULL;
     }
 
-    max_len = iv_len + aad_len + src_len + dst_len + hash_result_len;
+    max_len = (uint64_t)iv_len + aad_len + src_len + dst_len + hash_result_len;
     if (unlikely(max_len > vcrypto->conf.max_size)) {
         virtio_error(vdev, "virtio-crypto too big length");
         return NULL;