RE: [PATCH v3 4/5] virtio-crypto: adjust dst_len at ops callback

["Gonglei \(Arei\) via Virtualization" <virtualization@lists.linux-foundation.org>]

> -----Original Message-----
> From: zhenwei pi [mailto:pizhenwei@bytedance.com]
> Sent: Thursday, April 21, 2022 6:40 PM
> To: Gonglei (Arei) <arei.gonglei@huawei.com>; mst@redhat.com
> Cc: jasowang@redhat.com; herbert@gondor.apana.org.au;
> linux-kernel@vger.kernel.org; virtualization@lists.linux-foundation.org;
> linux-crypto@vger.kernel.org; helei.sig11@bytedance.com;
> davem@davemloft.net; zhenwei pi <pizhenwei@bytedance.com>
> Subject: [PATCH v3 4/5] virtio-crypto: adjust dst_len at ops callback
> 
> From: lei he <helei.sig11@bytedance.com>
> 
> For some akcipher operations(eg, decryption of pkcs1pad(rsa)), the length of
> returned result maybe less than akcipher_req->dst_len, we need to recalculate
> the actual dst_len through the virt-queue protocol.
> 
OK ...

> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Jason Wang <jasowang@redhat.com>
> Cc: Gonglei <arei.gonglei@huawei.com>
> Signed-off-by: lei he <helei.sig11@bytedance.com>
> Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
> ---
>  drivers/crypto/virtio/virtio_crypto_akcipher_algs.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/crypto/virtio/virtio_crypto_akcipher_algs.c
> b/drivers/crypto/virtio/virtio_crypto_akcipher_algs.c
> index 9561bc2df62b..82db86e088c2 100644
> --- a/drivers/crypto/virtio/virtio_crypto_akcipher_algs.c
> +++ b/drivers/crypto/virtio/virtio_crypto_akcipher_algs.c
> @@ -90,9 +90,12 @@ static void
> virtio_crypto_dataq_akcipher_callback(struct virtio_crypto_request *
>  	}
> 
>  	akcipher_req = vc_akcipher_req->akcipher_req;
> -	if (vc_akcipher_req->opcode != VIRTIO_CRYPTO_AKCIPHER_VERIFY)
> +	if (vc_akcipher_req->opcode != VIRTIO_CRYPTO_AKCIPHER_VERIFY) {
> +		/* actuall length maybe less than dst buffer */
> +		akcipher_req->dst_len = len - sizeof(vc_req->status);

...but why minus sizeof(vc_req->status)?


Regards,
-Gonglei


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