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Date:   Thu, 31 Aug 2023 15:37:50 +0200
From:   Florian Westphal <fw@strlen.de>
To:     Wander Lairson Costa <wander@redhat.com>
Cc:     Pablo Neira Ayuso <pablo@netfilter.org>,
        Jozsef Kadlecsik <kadlec@netfilter.org>,
        Florian Westphal <fw@strlen.de>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Fernando Fernandez Mancera <ffmancera@riseup.net>,
        "open list:NETFILTER" <netfilter-devel@vger.kernel.org>,
        "open list:NETFILTER" <coreteam@netfilter.org>,
        "open list:NETWORKING [GENERAL]" <netdev@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        Lucas Leong <wmliang@infosec.exchange>, stable@kernel.org
Subject: Re: [PATCH nf v2] netfilter/osf: avoid OOB read
Message-ID: <20230831133750.GB15759@breakpoint.cc>
References: <20230831123931.60606-1-wander@redhat.com>
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Wander Lairson Costa <wander@redhat.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.