From: Kees Cook <k...@kernel.org> Date: Mon, 16 Dec 2024 18:59:55 -0800
> This switches to using a manually constructed form of struct tagging > to avoid issues with C++ being unable to parse tagged structs within > anonymous unions, even under 'extern "C"': > > ../linux/include/uapi/linux/pkt_cls.h:25124: error: ‘struct > tc_u32_sel::<unnamed union>::tc_u32_sel_hdr,’ invalid; an anonymous union may > only have public non-static data members [-fpermissive] I worked around that like this in the past: [0] As I'm not sure it would be fine to fix every such occurrence manually by open-coding. What do you think? > > To avoid having multiple struct member lists, use a define to declare > them. > > Reported-by: cfer...@google.com > Closes: https://lore.kernel.org/linux-hardening/z1hzpe3we5as8...@google.com/ > Fixes: 216203bdc228 ("UAPI: net/sched: Use __struct_group() in flex struct > tc_u32_sel") > Link: https://lore.kernel.org/r/202412120927.943DFEDD@keescook > Signed-off-by: Kees Cook <k...@kernel.org> > --- > Cc: Jakub Kicinski <k...@kernel.org> > Cc: Jamal Hadi Salim <j...@mojatatu.com> > Cc: Cong Wang <xiyou.wangc...@gmail.com> > Cc: Jiri Pirko <j...@resnulli.us> > Cc: net...@vger.kernel.org > --- > include/uapi/linux/pkt_cls.h | 34 +++++++++++++++++++++------------- > 1 file changed, 21 insertions(+), 13 deletions(-) > > diff --git a/include/uapi/linux/pkt_cls.h b/include/uapi/linux/pkt_cls.h > index 2c32080416b5..02aee6ed6bf0 100644 > --- a/include/uapi/linux/pkt_cls.h > +++ b/include/uapi/linux/pkt_cls.h > @@ -245,20 +245,28 @@ struct tc_u32_key { > int offmask; > }; > > +#define tc_u32_sel_hdr_members \ > + unsigned char flags; \ > + unsigned char offshift; \ > + unsigned char nkeys; \ > + __be16 offmask; \ > + __u16 off; \ > + short offoff; \ > + short hoff; \ > + __be32 hmask > + > +struct tc_u32_sel_hdr { > + tc_u32_sel_hdr_members; > +}; > + > struct tc_u32_sel { > - /* New members MUST be added within the __struct_group() macro below. */ > - __struct_group(tc_u32_sel_hdr, hdr, /* no attrs */, > - unsigned char flags; > - unsigned char offshift; > - unsigned char nkeys; > - > - __be16 offmask; > - __u16 off; > - short offoff; > - > - short hoff; > - __be32 hmask; > - ); > + /* Open-coded struct_group() to avoid C++ errors. */ > + union { > + struct tc_u32_sel_hdr hdr; > + struct { > + tc_u32_sel_hdr_members; > + }; > + }; > struct tc_u32_key keys[]; > }; [0] https://github.com/alobakin/linux/commit/2a065c7bae821f5fa85fff6f97fbbd460f4aa0f3 Thanks, Olek
