Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Tue, 26 Nov 2019 12:06:03 +0100 | Subject | nf_flow on big-endian (was: Re: linux-next: build warning after merge of the net-next tree) |
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On Thu, Nov 21, 2019 at 8:36 AM Stephen Rothwell <sfr@canb.auug.org.au> wrote: > After merging the net-next tree, today's linux-next build (powerpc > allyesconfig) produced this warning: > > net/netfilter/nf_flow_table_offload.c: In function 'nf_flow_rule_match': > net/netfilter/nf_flow_table_offload.c:80:21: warning: unsigned conversion from 'int' to '__be16' {aka 'short unsigned int'} changes value from '327680' to '0' [-Woverflow] > 80 | mask->tcp.flags = TCP_FLAG_RST | TCP_FLAG_FIN; > | ^~~~~~~~~~~~ > > Introduced by commit > > c29f74e0df7a ("netfilter: nf_flow_table: hardware offload support")
This is now upstream, and must be completely broken on big-endian platforms.
The other user of the flags field looks buggy, too (net/core/flow_dissector.c:__skb_flow_dissect_tcp()[*]):
key_tcp->flags = (*(__be16 *) &tcp_flag_word(th) & htons(0x0FFF));
Disclaimer: I'm not familiar with the code or protocol, so below are just my gut feelings.
struct flow_dissector_key_tcp { __be16 flags; };
Does this have to be __be16, i.e. does it go over the wire? If not, this should probably be __u16, and set using "be32_to_cpu(flags) >> 16"? If yes, "cpu_to_be16(be32_to_cpu(flags) >> 16)"? (Ugh, needs convenience macros)
[*] ac4bb5de27010e41 ("net: flow_dissector: add support for dissection of tcp flags")
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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