linux-kernel - Re: [PATCH v5] audit: log nftables configuration change events once per table

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Message-ID: <20210331205310.GA3141668@madcap2.tricolour.ca>
Date:   Wed, 31 Mar 2021 16:53:10 -0400
From:   Richard Guy Briggs <rgb@...hat.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>
Cc:     Linux-Audit Mailing List <linux-audit@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        netfilter-devel@...r.kernel.org, Paul Moore <paul@...l-moore.com>,
        Eric Paris <eparis@...isplace.org>,
        Steve Grubb <sgrubb@...hat.com>,
        Florian Westphal <fw@...len.de>, Phil Sutter <phil@....cc>,
        twoerner@...hat.com, tgraf@...radead.org, dan.carpenter@...cle.com,
        Jones Desougi <jones.desougi+netfilter@...il.com>
Subject: Re: [PATCH v5] audit: log nftables configuration change events once
 per table

On 2021-03-31 22:22, Pablo Neira Ayuso wrote:
> On Fri, Mar 26, 2021 at 01:38:59PM -0400, Richard Guy Briggs wrote:
> > Reduce logging of nftables events to a level similar to iptables.
> > Restore the table field to list the table, adding the generation.
> > 
> > Indicate the op as the most significant operation in the event.
> 
> There's a UAF, Florian reported. I'm attaching an incremental fix.
> 
> nf_tables_commit_audit_collect() refers to the trans object which
> might have been already released.

Got it.  Thanks Pablo.  I didn't see it when running nft-test.py Where
was it reported?  Here I tried to stay out of the way by putting that
call at the end of the loop but that was obviously a mistake in
hindsight.  :-)

> commit e4d272948d25b66d86fc241cefd95281bfb1079e
> Author: Pablo Neira Ayuso <pablo@...filter.org>
> Date:   Wed Mar 31 22:19:51 2021 +0200
> 
>     netfilter: nf_tables: use-after-free
>     
>     Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
> 
> diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> index 5dd4bb7cabf5..01674c0d9103 100644
> --- a/net/netfilter/nf_tables_api.c
> +++ b/net/netfilter/nf_tables_api.c
> @@ -8063,6 +8063,8 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb)
>  	net->nft.gencursor = nft_gencursor_next(net);
>  
>  	list_for_each_entry_safe(trans, next, &net->nft.commit_list, list) {
> +		nf_tables_commit_audit_collect(&adl, trans->ctx.table,
> +					       trans->msg_type);
>  		switch (trans->msg_type) {
>  		case NFT_MSG_NEWTABLE:
>  			if (nft_trans_table_update(trans)) {
> @@ -8211,8 +8213,6 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb)
>  			}
>  			break;
>  		}
> -		nf_tables_commit_audit_collect(&adl, trans->ctx.table,
> -					       trans->msg_type);
>  	}
>  
>  	nft_commit_notify(net, NETLINK_CB(skb).portid);


- RGB

--
Richard Guy Briggs <rgb@...hat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635