Re: [PATCH v2 7/9] crypto: virtio: Add IV buffer in structure virtio_crypto_sym_request

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Dec 04, 2025 at 07:25:02PM +0800, Bibo Mao wrote:
> Add IV buffer in structure virtio_crypto_sym_request to avoid unnecessary
> IV buffer allocation in encrypt/decrypt process. And IV buffer is cleared
> when encrypt/decrypt is finished.
> 
> Signed-off-by: Bibo Mao <maobibo@loongson.cn>
> ---
>  .../virtio/virtio_crypto_skcipher_algs.c      | 20 +++++++------------
>  1 file changed, 7 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/crypto/virtio/virtio_crypto_skcipher_algs.c b/drivers/crypto/virtio/virtio_crypto_skcipher_algs.c
> index a7c7c726e6d9..c911b7ba8f13 100644
> --- a/drivers/crypto/virtio/virtio_crypto_skcipher_algs.c
> +++ b/drivers/crypto/virtio/virtio_crypto_skcipher_algs.c
> @@ -30,9 +30,9 @@ struct virtio_crypto_sym_request {
>  
>  	/* Cipher or aead */
>  	uint32_t type;
> -	uint8_t *iv;
>  	/* Encryption? */
>  	bool encrypt;
> +	uint8_t iv[0];
>  };
>  
>  struct virtio_crypto_algo {
> @@ -402,12 +402,7 @@ __virtio_crypto_skcipher_do_req(struct virtio_crypto_sym_request *vc_sym_req,
>  	 * Avoid to do DMA from the stack, switch to using
>  	 * dynamically-allocated for the IV
>  	 */
> -	iv = kzalloc_node(ivsize, GFP_ATOMIC,
> -				dev_to_node(&vcrypto->vdev->dev));
> -	if (!iv) {
> -		err = -ENOMEM;
> -		goto free;
> -	}
> +	iv = vc_sym_req->iv;
>  	memcpy(iv, req->iv, ivsize);
>  	if (!vc_sym_req->encrypt)
>  		scatterwalk_map_and_copy(req->iv, req->src,
> @@ -416,7 +411,6 @@ __virtio_crypto_skcipher_do_req(struct virtio_crypto_sym_request *vc_sym_req,
>  
>  	sg_init_one(&iv_sg, iv, ivsize);
>  	sgs[num_out++] = &iv_sg;
> -	vc_sym_req->iv = iv;
>  
>  	/* Source data */
>  	for (sg = req->src; src_nents; sg = sg_next(sg), src_nents--)
> @@ -438,12 +432,10 @@ __virtio_crypto_skcipher_do_req(struct virtio_crypto_sym_request *vc_sym_req,
>  	virtqueue_kick(data_vq->vq);
>  	spin_unlock_irqrestore(&data_vq->lock, flags);
>  	if (unlikely(err < 0))
> -		goto free_iv;
> +		goto free;
>  
>  	return 0;
>  
> -free_iv:
> -	kfree_sensitive(iv);

so iv is no longer cleared on error. problem?

>  free:
>  	kfree(sgs);
>  	return err;
> @@ -501,8 +493,10 @@ static int virtio_crypto_skcipher_init(struct crypto_skcipher *tfm)
>  {
>  	struct virtio_crypto_skcipher_ctx *ctx = crypto_skcipher_ctx(tfm);
>  	struct skcipher_alg *alg = crypto_skcipher_alg(tfm);
> +	int size;
>  
> -	crypto_skcipher_set_reqsize(tfm, sizeof(struct virtio_crypto_sym_request));
> +	size = sizeof(struct virtio_crypto_sym_request) + crypto_skcipher_ivsize(tfm);
> +	crypto_skcipher_set_reqsize(tfm, size);
>  	ctx->alg = container_of(alg, struct virtio_crypto_algo, algo.base);
>  
>  	return 0;
> @@ -552,7 +546,7 @@ static void virtio_crypto_skcipher_finalize_req(
>  		scatterwalk_map_and_copy(req->iv, req->dst,
>  					 req->cryptlen - ivsize,
>  					 ivsize, 0);
> -	kfree_sensitive(vc_sym_req->iv);
> +	memzero_explicit(vc_sym_req->iv, ivsize);
>  	virtcrypto_clear_request(&vc_sym_req->base);
>  
>  	crypto_finalize_skcipher_request(vc_sym_req->base.dataq->engine,
> -- 
> 2.39.3