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

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Message-ID: <20231103091801.GA8035@breakpoint.cc>
Date:   Fri, 3 Nov 2023 10:18:01 +0100
From:   Florian Westphal <fw@...len.de>
To:     Dan Carpenter <dan.carpenter@...aro.org>
Cc:     Florian Westphal <fw@...len.de>,
        Pablo Neira Ayuso <pablo@...filter.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()

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.