netdev - Re: [RESEND PATCH v3] virtio_net: Fix mismatched buf address when unmapping for small packets

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <1726729783.1689022-1-xuanzhuo@linux.alibaba.com>
Date: Thu, 19 Sep 2024 15:09:43 +0800
From: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To: Wenbo Li <liwenbo.martin@...edance.com>
Cc: virtualization@...ts.linux.dev,
 netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 Wenbo Li <liwenbo.martin@...edance.com>,
 Jiahui Cen <cenjiahui@...edance.com>,
 Ying Fang <fangying.tommy@...edance.com>,
 mst@...hat.com,
 jasowang@...hat.com,
 eperezma@...hat.com,
 davem@...emloft.net,
 edumazet@...gle.com,
 kuba@...nel.org,
 pabeni@...hat.com
Subject: Re: [RESEND PATCH v3] virtio_net: Fix mismatched buf address when unmapping for small packets

On Thu, 19 Sep 2024 11:52:14 +0800, Wenbo Li <liwenbo.martin@...edance.com> wrote:
> Currently, the virtio-net driver will perform a pre-dma-mapping for
> small or mergeable RX buffer. But for small packets, a mismatched address
> without VIRTNET_RX_PAD and xdp_headroom is used for unmapping.
>
> That will result in unsynchronized buffers when SWIOTLB is enabled, for
> example, when running as a TDX guest.
>
> This patch unifies the address passed to the virtio core into the address
> of the virtnet header and fixes the mismatched buffer address.
>
> Changes from v2: unify the buf that passed to the virtio core in small
> and merge mode.
> Changes from v1: Use ctx to get xdp_headroom.
>
> Fixes: 295525e29a5b ("virtio_net: merge dma operations when filling mergeable buffers")
> Signed-off-by: Wenbo Li <liwenbo.martin@...edance.com>
> Signed-off-by: Jiahui Cen <cenjiahui@...edance.com>
> Signed-off-by: Ying Fang <fangying.tommy@...edance.com>
> ---
>  drivers/net/virtio_net.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 6f4781ec2b36..9446666c84aa 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1804,9 +1804,15 @@ static struct sk_buff *receive_small(struct net_device *dev,
>  				     struct virtnet_rq_stats *stats)
>  {
>  	unsigned int xdp_headroom = (unsigned long)ctx;
> -	struct page *page = virt_to_head_page(buf);
> +	struct page *page;

Because that here is head page, so you can keep the original code.

>  	struct sk_buff *skb;
>
> +	// We passed the address of virtnet header to virtio-core,
> +	// so truncate the padding.

Please check the kernel code style.

Thanks.

> +	buf -= VIRTNET_RX_PAD + xdp_headroom;
> +
> +	page = virt_to_head_page(buf);
> +
>  	len -= vi->hdr_len;
>  	u64_stats_add(&stats->bytes, len);
>
> @@ -2422,8 +2428,9 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
>  	if (unlikely(!buf))
>  		return -ENOMEM;
>
> -	virtnet_rq_init_one_sg(rq, buf + VIRTNET_RX_PAD + xdp_headroom,
> -			       vi->hdr_len + GOOD_PACKET_LEN);
> +	buf += VIRTNET_RX_PAD + xdp_headroom;
> +
> +	virtnet_rq_init_one_sg(rq, buf, vi->hdr_len + GOOD_PACKET_LEN);
>
>  	err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1, buf, ctx, gfp);
>  	if (err < 0) {
> --
> 2.20.1
>