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

From: Pablo Neira Ayuso
Date: Wed Dec 11 2019 - 17:04:29 EST

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@xxxxxxxx>
> ---
> I'm not sure if this is the correct fix, please check carefully

Thanks. I posted this one:

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