On Fri, Oct 28, 2022 at 09:18:39AM +0200, Christian König wrote: > Am 28.10.22 um 07:10 schrieb Paulo Miguel Almeida: > > One-element arrays are deprecated, and we are replacing them with > > flexible array members instead. So, replace one-element array with > > flexible-array member in struct _ATOM_FAKE_EDID_PATCH_RECORD and > > refactor the rest of the code accordingly. > > > > This helps with the ongoing efforts to tighten the FORTIFY_SOURCE > > routines on memcpy() and help us make progress towards globally > > enabling -fstrict-flex-arrays=3 [1]. > > > > Link: https://github.com/KSPP/linux/issues/79 > > Link: https://github.com/KSPP/linux/issues/238 > > Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836 [1] > > I'm not sure if that's a good idea. We had multiple attempts to refactor > this now and it always caused a regression. > > Additional to that the header in question came from our BIOS team and isn't > following Linux styles in general. > > Alex what do you think? Fake flexible arrays (i.e. 1-element arrays) are deprecated in Linux[1] (and, frankly, deprecated in C since 1999 and even well before then given the 0-sized extension that was added in GCC), so we can't continue to bring them into kernel sources. Their use breaks both compile-time and run-time bounds checking efforts, etc. All that said, converting away from them can be tricky, and I think such conversions need to explicitly show how they were checked for binary differences[2]. Paulo, can you please check for deltas and report your findings in the commit log? Note that add struct_size() use in the same patch may result in binary differences, so for more complex cases, you may want to split the 1-element conversion from the struct_size() conversions. -Kees [1] https://docs.kernel.org/process/deprecated.html#zero-length-and-one-element-arrays [2] https://outflux.net/blog/archives/2022/06/24/finding-binary-differences/ -- Kees Cook
