Messages in this thread | | | Date | Fri, 4 Aug 2023 19:33:33 +0200 | Subject | Re: [PATCH net-next 1/3] virtchnl: fix fake 1-elem arrays in structs allocated as `nents + 1` - 1 | From | Alexander Lobakin <> |
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From: Kees Cook <keescook@chromium.org> Date: Fri, 4 Aug 2023 10:29:48 -0700
> On Fri, Aug 04, 2023 at 05:42:19PM +0200, Alexander Lobakin wrote: >> From: Kees Cook <keescook@chromium.org> >> Date: Fri, 4 Aug 2023 01:27:02 -0700 >> >>> On Fri, Jul 28, 2023 at 05:52:05PM +0200, Alexander Lobakin wrote: >>>> The two most problematic virtchnl structures are virtchnl_rss_key and >>>> virtchnl_rss_lut. Their "flex" arrays have the type of u8, thus, when >>>> allocating / checking, the actual size is calculated as `sizeof + >>>> nents - 1 byte`. But their sizeof() is not 1 byte larger than the size >>>> of such structure with proper flex array, it's two bytes larger due to >>>> the padding. That said, their size is always 1 byte larger unless >>>> there are no tail elements -- then it's +2 bytes. >>>> Add virtchnl_struct_size() macro which will handle this case (and later >>>> other cases as well). Make its calling conv the same as we call >>>> struct_size() to allow it to be drop-in, even though it's unlikely to >>>> become possible to switch to generic API. The macro will calculate a >>>> proper size of a structure with a flex array at the end, so that it >>>> becomes transparent for the compilers, but add the difference from the >>>> old values, so that the real size of sorta-ABI-messages doesn't change. >>>> Use it on the allocation side in IAVF and the receiving side (defined >>>> as static inline in virtchnl.h) for the mentioned two structures. >>>> >>>> Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com> >>> >>> This is a novel approach to solving the ABI issues for a 1-elem >>> conversion, but I have been convinced it's a workable approach here. :) >>> Thanks for doing this conversion! >>> >>> Reviewed-by: Kees Cook <keescook@chromium.org> >>> >> >> Thanks a lot! >> You gave Reviewed-by for patches #1 and #3, does it mean the whole >> series or something is wrong with the patch #2? :D > > Hm, maybe delivery was delayed? I see it on lore: > https://lore.kernel.org/all/202308040128.667940394B@keescook/ >
Nevermind, my mail rules did put it in the folder other than the one where the main thread was, sorry :s Much thanks, I'm now a fan of _Generic() too :D
Olek
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