linux-kernel - Re: [PATCH net] netfilter: nf_tables: fix pointer math issue in nft_byteorder

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Date: Tue, 6 Feb 2024 12:29:51 +0100
From: Pablo Neira Ayuso <pablo@...filter.org>
To: Florian Westphal <fw@...len.de>
Cc: Michal Kubecek <mkubecek@...e.cz>,
	Dan Carpenter <dan.carpenter@...aro.org>,
	Jozsef Kadlecsik <kadlec@...filter.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netfilter-devel@...r.kernel.org, coreteam@...filter.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org, andrea.mattiazzo@...e.com
Subject: Re: [PATCH net] netfilter: nf_tables: fix pointer math issue in
 nft_byteorder_eval()

On Tue, Feb 06, 2024 at 12:11:12PM +0100, Florian Westphal wrote:
> Michal Kubecek <mkubecek@...e.cz> wrote:
> > I stumbled upon this when the issue got a CVE id (sigh) and I share
> > Andrea's (Cc-ed) concern that the fix is incomplete. While the fix,
> > commit c301f0981fdd ("netfilter: nf_tables: fix pointer math issue in
> > nft_byteorder_eval()") now, fixes the destination side, src is still
> > a pointer to u32, i.e. we are reading 64-bit values with relative
> > offsets which are multiples of 32 bits.
> > 
> > Shouldn't we fix this as well, e.g. like indicated below?
> 
> No, please remove multi-elem support instead, nothing uses this feature.

See attached patch.

I posted this:

https://patchwork.ozlabs.org/project/netfilter-devel/patch/20240202120602.5122-1-pablo@netfilter.org/

I can replace it by the attached patch if you prefer. This can only
help in the future to microoptimize some set configurations, where
several byteorder can be coalesced into one single expression.

View attachment "remove-multiword.patch" of type "text/x-diff" (1959 bytes)