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Date:   Fri, 1 Sep 2023 10:15:06 +0200
From:   Pablo Neira Ayuso <pablo@netfilter.org>
To:     Jakub Kicinski <kuba@kernel.org>
Cc:     joao@overdrivepizza.com, netfilter-devel@vger.kernel.org,
        coreteam@netfilter.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, kadlec@netfilter.org, fw@strlen.de,
        davem@davemloft.net, edumazet@google.com, pabeni@redhat.com,
        rkannoth@marvell.com, wojciech.drewek@intel.com,
        steen.hegenlund@microhip.com, keescook@chromium.org,
        Joao Moreira <joao.moreira@intel.com>
Subject: Re: [PATCH 0/2] Prevent potential write out of bounds
Message-ID: <ZPGdihJLKXOj7rDI@calendula>
References: <20230901010437.126631-1-joao@overdrivepizza.com>
 <20230831182800.25e5d4d9@kernel.org>
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On Thu, Aug 31, 2023 at 06:28:00PM -0700, Jakub Kicinski wrote:
> On Thu, 31 Aug 2023 18:04:35 -0700 joao@overdrivepizza.com wrote:
> > The function flow_rule_alloc in net/core/flow_offload.c [2] gets an
> > unsigned int num_actions (line 10) and later traverses the actions in
> > the rule (line 24) setting hw.stats to FLOW_ACTION_HW_STATS_DONT_CARE.
> > 
> > Within the same file, the loop in the line 24 compares a signed int
> > (i) to an unsigned int (num_actions), and then uses i as an array
> > index. If an integer overflow happens, then the array within the loop
> > is wrongly indexed, causing a write out of bounds.
> > 
> > After checking with maintainers, it seems that the front-end caps the
> > maximum value of num_action, thus it is not possible to reach the given
> > write out of bounds, yet, still, to prevent disasters it is better to
> > fix the signedness here.
> 
> How did you find this? The commit messages should include info
> about how the issue was discovered.

This is net-next material IMO, none of the existing interfaces uses
such a large number of actions for this to be an issue.