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Message-ID: <64e378e1c7fed_1b7a7294fd@willemb.c.googlers.com.notmuch> Date: Mon, 21 Aug 2023 10:46:57 -0400 From: Willem de Bruijn <willemdebruijn.kernel@...il.com> To: Feng Liu <feliu@...dia.com>, virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Cc: Jason Wang <jasowang@...hat.com>, "Michael S . Tsirkin" <mst@...hat.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, "David S . Miller" <davem@...emloft.net>, Willem de Bruijn <willemdebruijn.kernel@...il.com>, Simon Horman <horms@...nel.org>, Bodong Wang <bodong@...dia.com>, Feng Liu <feliu@...dia.com>, Jiri Pirko <jiri@...dia.com> Subject: Re: [PATCH net-next v3] virtio_net: Introduce skb_vnet_common_hdr to avoid typecasting Feng Liu wrote: > The virtio_net driver currently deals with different versions and types > of virtio net headers, such as virtio_net_hdr_mrg_rxbuf, > virtio_net_hdr_v1_hash, etc. Due to these variations, the code relies > on multiple type casts to convert memory between different structures, > potentially leading to bugs when there are changes in these structures. > > Introduces the "struct skb_vnet_common_hdr" as a unifying header > structure using a union. With this approach, various virtio net header > structures can be converted by accessing different members of this > structure, thus eliminating the need for type casting and reducing the > risk of potential bugs. > > For example following code: > static struct sk_buff *page_to_skb(struct virtnet_info *vi, > struct receive_queue *rq, > struct page *page, unsigned int offset, > unsigned int len, unsigned int truesize, > unsigned int headroom) > { > [...] > struct virtio_net_hdr_mrg_rxbuf *hdr; > [...] > hdr_len = vi->hdr_len; > [...] > ok: > hdr = skb_vnet_hdr(skb); > memcpy(hdr, hdr_p, hdr_len); > [...] > } > > When VIRTIO_NET_F_HASH_REPORT feature is enabled, hdr_len = 20 > But the sizeof(*hdr) is 12, > memcpy(hdr, hdr_p, hdr_len); will copy 20 bytes to the hdr, > which make a potential risk of bug. And this risk can be avoided by > introducing struct skb_vnet_common_hdr. > > Change log > v1->v2 > feedback from Willem de Bruijn <willemdebruijn.kernel@...il.com> > feedback from Simon Horman <horms@...nel.org> > 1. change to use net-next tree. > 2. move skb_vnet_common_hdr inside kernel file instead of the UAPI header. > > v2->v3 > feedback from Willem de Bruijn <willemdebruijn.kernel@...il.com> > 1. fix typo in commit message. > 2. add original struct virtio_net_hdr into union > 3. remove virtio_net_hdr_mrg_rxbuf variable in receive_buf; > > Signed-off-by: Feng Liu <feliu@...dia.com> > Reviewed-by: Jiri Pirko <jiri@...dia.com> Reviewed-by: Willem de Bruijn <willemb@...gle.com> A similar solution as tpacket_uhdr.
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