On Wed, Oct 16, 2024 at 04:18:19AM +0200, Jan Hendrik Farr wrote: > On 15 18:22:50, Bill Wendling wrote: > > On Thu, Oct 3, 2024 at 4:33 AM Jan Hendrik Farr <ker...@jfarr.cc> wrote: > > > On 02 11:18:57, Thorsten Blum wrote: > > > > On 28. Sep 2024, at 22:34, Kees Cook <k...@kernel.org> wrote: > > > > > [...] > > > > > > > > > > Sorry, I've been out of commission with covid. Globally disabling this > > > > > macro for clang is not the right solution (way too big a hammer). > > > > > > > > > > Until Bill has a fix, we can revert commit > > > > > 86e92eeeb23741a072fe7532db663250ff2e726a, as the problem is limited to > > > > > certain situations where 'counted_by' is in use. > > > > > > > > I already encountered two other related __counted_by() issues [1][2] > > > > that are now being reverted. Would it be an option to disable it > > > > globally, but only for Clang < v19 (where it looks like it'll be fixed)? > > > > > > > > Otherwise adding __counted_by() might be a slippery slope for a long > > > > time and the edge cases don't seem to be that rare anymore. > > > > > > > > Thanks, > > > > Thorsten > > > > > > > > [1] > > > > https://lore.kernel.org/all/20240909162725.1805-2-thorsten.b...@toblux.com/ > > > > [2] > > > > https://lore.kernel.org/all/20240923213809.235128-2-thorsten.b...@linux.dev/ > > > > > > This issue is now fixed on the llvm main branch: > > > https://github.com/llvm/llvm-project/commit/882457a2eedbe6d53161b2f78fcf769fc9a93e8a > > > > > > So presumably this will go into 19.1.2, not sure what this means for > > > distros that ship clang 18. Will they have to be notified to backport > > > this? > > > > > FYI, Clang 19.1.2 shipped with your fix in it. > > > > Thx for the info. > > How should we continue with the "off by 4" issue? The way I see it either > the kernel has to change struct_size (lots of work) or clang has to get > an option to follow the kernels behavior. I'm in favor of adding an > option to clang.
I'm planning on checking how much impact there is on the kernel to fix struct_size() to be precise. It really does need to match __bdos for Clang and GCC. -Kees -- Kees Cook
