On Thu, Aug 19, 2021 at 09:57:36AM +0900, Masahiro Yamada wrote: > cmd_update_lto_symversions merges all the existing *.symversions, but > some of them might be stale. > > If the last EXPORT_SYMBOL is removed from a C file, the *.symversions > file is not deleted or updated. It contains stale CRCs, which will be > used for linking the vmlinux or modules. > > It is not a big deal when the EXPORT_SYMBOL is really removed. However, > when the EXPORT_SYMBOL is moved to another file, the same __crc_<symbol> > will appear twice in the merged *.symversions, possibly with different > CRCs if the function argument is changed at the same time. It would > cause potential breakage of module versioning. > > If no EXPORT_SYMBOL is found, let's remove *.symversions explicitly. Ah, and this was an issue for non-LTO builds too? Regardless, nice catch. Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> -Kees > > Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx> > --- > > scripts/Makefile.build | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/scripts/Makefile.build b/scripts/Makefile.build > index 279363266455..585dae34746a 100644 > --- a/scripts/Makefile.build > +++ b/scripts/Makefile.build > @@ -177,6 +177,8 @@ cmd_modversions_c = \ > if $(NM) $@ 2>/dev/null | grep -q __ksymtab; then \ > $(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes)) \ > > $@.symversions; \ > + else \ > + rm -f $@.symversions; \ > fi; > else > cmd_modversions_c = \ > -- > 2.30.2 > -- Kees Cook
