netdev - Re: [PATCH] netfilter: nf_flow_table: fix big-endian integer overflow

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Date:   Wed, 11 Dec 2019 23:04:21 +0100
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>,
        "David S. Miller" <davem@...emloft.net>, wenxu <wenxu@...oud.cn>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] netfilter: nf_flow_table: fix big-endian integer overflow

Hi Arnd,

On Tue, Dec 10, 2019 at 09:24:28PM +0100, Arnd Bergmann wrote:
> In some configurations, gcc reports an integer overflow:
> 
> net/netfilter/nf_flow_table_offload.c: In function 'nf_flow_rule_match':
> net/netfilter/nf_flow_table_offload.c:80:21: error: unsigned conversion from 'int' to '__be16' {aka 'short unsigned int'} changes value from '327680' to '0' [-Werror=overflow]
>    mask->tcp.flags = TCP_FLAG_RST | TCP_FLAG_FIN;
>                      ^~~~~~~~~~~~
> 
> From what I can tell, we want the upper 16 bits of these constants,
> so they need to be shifted in cpu-endian mode.
> 
> Fixes: c29f74e0df7a ("netfilter: nf_flow_table: hardware offload support")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> I'm not sure if this is the correct fix, please check carefully

Thanks. I posted this one:

https://patchwork.ozlabs.org/patch/1206384/

The flow dissector matching on tcp flags seems also broken on big-endian.