netdev - Re: [PATCH net] rtnetlink: Disallow FDB configuration for non-Ethernet device

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Message-ID: <03983d49-664a-12d6-ede4-e16a37af4563@gmail.com>
Date:   Sun, 28 Oct 2018 15:37:38 -0600
From:   David Ahern <dsahern@...il.com>
To:     Ido Schimmel <idosch@...lanox.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Cc:     "davem@...emloft.net" <davem@...emloft.net>,
        Vlad Yasevich <vyasevich@...il.com>
Subject: Re: [PATCH net] rtnetlink: Disallow FDB configuration for
 non-Ethernet device

On 10/27/18 2:39 PM, Ido Schimmel wrote:
> When an FDB entry is configured, the address is validated to have the
> length of an Ethernet address, but the device for which the address is
> configured can be of any type.
> 
> The above can result in the use of uninitialized memory when the address
> is later compared against existing addresses since 'dev->addr_len' is
> used and it may be greater than ETH_ALEN, as with ip6tnl devices.
> 
> Fix this by making sure that FDB entries are only configured for
> Ethernet devices.

...

> 
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index f679c7a7d761..728a97f9f700 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -3600,6 +3600,11 @@ static int rtnl_fdb_add(struct sk_buff *skb, struct nlmsghdr *nlh,
>  		return -EINVAL;
>  	}
>  
> +	if (dev->type != ARPHRD_ETHER) {
> +		NL_SET_ERR_MSG(extack, "invalid device type");

If only Ethernet devices are supported, then the error message can be
more specific: "FDB add only support for Ethernet devices"

> +		return -EINVAL;
> +	}
> +
>  	addr = nla_data(tb[NDA_LLADDR]);
>  
>  	err = fdb_vid_parse(tb[NDA_VLAN], &vid, extack);
> @@ -3704,6 +3709,11 @@ static int rtnl_fdb_del(struct sk_buff *skb, struct nlmsghdr *nlh,
>  		return -EINVAL;
>  	}
>  
> +	if (dev->type != ARPHRD_ETHER) {
> +		NL_SET_ERR_MSG(extack, "invalid device type");

same here.


> +		return -EINVAL;
> +	}
> +
>  	addr = nla_data(tb[NDA_LLADDR]);
>  
>  	err = fdb_vid_parse(tb[NDA_VLAN], &vid, extack);
>