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Message-ID: <20231103102546.GB8035@breakpoint.cc>
Date: Fri, 3 Nov 2023 11:25:46 +0100
From: Florian Westphal <fw@...len.de>
To: Pablo Neira Ayuso <pablo@...filter.org>
Cc: Florian Westphal <fw@...len.de>,
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
Subject: Re: [PATCH net] netfilter: nf_tables: fix pointer math issue in
nft_byteorder_eval()
Pablo Neira Ayuso <pablo@...filter.org> wrote:
> On Fri, Nov 03, 2023 at 10:18:01AM +0100, Florian Westphal wrote:
> > Dan Carpenter <dan.carpenter@...aro.org> wrote:
> > > The problem is in nft_byteorder_eval() where we are iterating through a
> > > loop and writing to dst[0], dst[1], dst[2] and so on... On each
> > > iteration we are writing 8 bytes. But dst[] is an array of u32 so each
> > > element only has space for 4 bytes. That means that every iteration
> > > overwrites part of the previous element.
> > >
> > > I spotted this bug while reviewing commit caf3ef7468f7 ("netfilter:
> > > nf_tables: prevent OOB access in nft_byteorder_eval") which is a related
> > > issue. I think that the reason we have not detected this bug in testing
> > > is that most of time we only write one element.
> >
> > LGTM, thanks Dan. We will route this via nf.git.
>
> Thanks for your patch.
>
> One question, is this update really required?
I think so, yes. Part of this bug here is that this helper-niceness
masks whats really happening in the caller (advancing in strides of
'u32', rather than 'u64').
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