linux-kernel - Re: [PATCH] crypto: virtio - Erase some sensitive memory when it is freed

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Message-ID: <CAPpAL=wW6szqfPm8goUfM=c2cat9-tyuB-UgwRdtx7s23xe81g@mail.gmail.com>
Date: Tue, 4 Mar 2025 09:59:33 +0800
From: Lei Yang <leiyang@...hat.com>
To: Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc: "Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>, 
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Eugenio Pérez <eperezma@...hat.com>, 
	Gonglei <arei.gonglei@...wei.com>, Herbert Xu <herbert@...dor.apana.org.au>, 
	"David S. Miller" <davem@...emloft.net>, linux-kernel@...r.kernel.org, 
	kernel-janitors@...r.kernel.org, virtualization@...ts.linux.dev, 
	linux-crypto@...r.kernel.org
Subject: Re: [PATCH] crypto: virtio - Erase some sensitive memory when it is freed

QE tested this patch with virtio-net regression tests, everything works fine.

Tested-by: Lei Yang <leiyang@...hat.com>

On Tue, Mar 4, 2025 at 3:08 AM Christophe JAILLET
<christophe.jaillet@...adoo.fr> wrote:
>
> virtcrypto_clear_request() does the same as the code here, but uses
> kfree_sensitive() for one of the free operation.
>
> So, better safe than sorry, use virtcrypto_clear_request() directly to
> save a few lines of code and cleanly free the memory.
>
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---
> I've no idea if this is needed or not, but it looks not consistent to me.
>
> If safe as-is, maybe the kfree_sensitive() in virtcrypto_clear_request()
> should be removed instead.
> ---
>  drivers/crypto/virtio/virtio_crypto_core.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/crypto/virtio/virtio_crypto_core.c b/drivers/crypto/virtio/virtio_crypto_core.c
> index d0278eb568b9..0d522049f595 100644
> --- a/drivers/crypto/virtio/virtio_crypto_core.c
> +++ b/drivers/crypto/virtio/virtio_crypto_core.c
> @@ -480,10 +480,8 @@ static void virtcrypto_free_unused_reqs(struct virtio_crypto *vcrypto)
>
>         for (i = 0; i < vcrypto->max_data_queues; i++) {
>                 vq = vcrypto->data_vq[i].vq;
> -               while ((vc_req = virtqueue_detach_unused_buf(vq)) != NULL) {
> -                       kfree(vc_req->req_data);
> -                       kfree(vc_req->sgs);
> -               }
> +               while ((vc_req = virtqueue_detach_unused_buf(vq)) != NULL)
> +                       virtcrypto_clear_request(vc_req);
>                 cond_resched();
>         }
>  }
> --
> 2.48.1
>
>