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

[Bibo Mao]

On 2025/12/4 下午8:48, Michael S. Tsirkin wrote:

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 <maob...@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?

yes, it is a problem, IV buffer should be cleared on error.
Will fix on next version.

Regards
Bibo Mao

  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