netdev - Re: [PATCH nf v2] netfilter/osf: avoid OOB read

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Message-ID: <20230831133750.GB15759@breakpoint.cc>
Date: Thu, 31 Aug 2023 15:37:50 +0200
From: Florian Westphal <fw@...len.de>
To: Wander Lairson Costa <wander@...hat.com>
Cc: Pablo Neira Ayuso <pablo@...filter.org>,
	Jozsef Kadlecsik <kadlec@...filter.org>,
	Florian Westphal <fw@...len.de>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Fernando Fernandez Mancera <ffmancera@...eup.net>,
	"open list:NETFILTER" <netfilter-devel@...r.kernel.org>,
	"open list:NETFILTER" <coreteam@...filter.org>,
	"open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>,
	Lucas Leong <wmliang@...osec.exchange>, stable@...nel.org
Subject: Re: [PATCH nf v2] netfilter/osf: avoid OOB read

Wander Lairson Costa <wander@...hat.com> wrote:
> 
> diff --git a/net/netfilter/nfnetlink_osf.c b/net/netfilter/nfnetlink_osf.c
> index 8f1bfa6ccc2d..13fedf2aaa0f 100644
> --- a/net/netfilter/nfnetlink_osf.c
> +++ b/net/netfilter/nfnetlink_osf.c
> @@ -315,6 +315,9 @@ static int nfnl_osf_add_callback(struct sk_buff *skb,
>  
>  	f = nla_data(osf_attrs[OSF_ATTR_FINGER]);
>  
> +	if (f->opt_num > ARRAY_SIZE(f->opt))
> +		return -EINVAL;
> +

Hmm, this isn't enough; as far as I can see there is no validation
whatsover.

This should also check that all of:

 char    genre[MAXGENRELEN];
 char    version[MAXGENRELEN];
 char    subtype[MAXGENRELEN];

... have a NUL byte.  You could use strnlen() == ARRAY_SIZE() -> EINVAL
for those.

Maybe there is more to be validated, I did not followup with all the
nested structures buried in user_finger struct.