netdev - Re: [PATCH net-next v13 11/12] virtio_net: Add support for TCP and UDP ethtool rules

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Message-ID: <aS8L--z0ezhkywT_@horms.kernel.org>
Date: Tue, 2 Dec 2025 15:55:39 +0000
From: Simon Horman <horms@...nel.org>
To: Daniel Jurgens <danielj@...dia.com>
Cc: netdev@...r.kernel.org, mst@...hat.com, jasowang@...hat.com,
	pabeni@...hat.com, virtualization@...ts.linux.dev, parav@...dia.com,
	shshitrit@...dia.com, yohadt@...dia.com, xuanzhuo@...ux.alibaba.com,
	eperezma@...hat.com, jgg@...pe.ca, kevin.tian@...el.com,
	kuba@...nel.org, andrew+netdev@...n.ch, edumazet@...gle.com
Subject: Re: [PATCH net-next v13 11/12] virtio_net: Add support for TCP and
 UDP ethtool rules

On Wed, Nov 26, 2025 at 01:35:38PM -0600, Daniel Jurgens wrote:

...

> @@ -6005,6 +6085,11 @@ static void parse_ip4(struct iphdr *mask, struct iphdr *key,
>  		mask->tos = l3_mask->tos;
>  		key->tos = l3_val->tos;
>  	}
> +
> +	if (l3_mask->proto) {
> +		mask->protocol = l3_mask->proto;
> +		key->protocol = l3_val->proto;
> +	}
>  }

Hi Daniel,

Claude Code with review-prompts flags an issue here,
which I can't convince myself is not the case.

If parse_ip4() is called for a IP_USER_FLOW, which use ethtool_usrip4_spec,
as does this function, then all is well.

However, it seems that it may also be called for TCP_V4_FLOW and UDP_V4_FLOW
flows, in which case accessing .proto will overrun the mask and key which
are actually struct ethtool_tcpip4_spec.

https://netdev-ai.bots.linux.dev/ai-review.html?id=51d97b85-5ca3-4cb8-a96a-0d6eab5e7196#patch-10

>  
>  static void parse_ip6(struct ipv6hdr *mask, struct ipv6hdr *key,
> @@ -6022,16 +6107,35 @@ static void parse_ip6(struct ipv6hdr *mask, struct ipv6hdr *key,
>  		memcpy(&mask->daddr, l3_mask->ip6dst, sizeof(mask->daddr));
>  		memcpy(&key->daddr, l3_val->ip6dst, sizeof(key->daddr));
>  	}
> +
> +	if (l3_mask->l4_proto) {
> +		mask->nexthdr = l3_mask->l4_proto;
> +		key->nexthdr = l3_val->l4_proto;
> +	}

Likewise here.

>  }

...