Messages in this thread | | | From | Masahiro Yamada <> | Date | Wed, 4 Oct 2017 23:33:38 +0900 | Subject | Re: [PATCH 2/3] Makefile: Move stackprotector availability out of Kconfig |
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Hi Kees,
2017-10-03 4:20 GMT+09:00 Kees Cook <keescook@chromium.org>: > Various portions of the kernel, especially per-architecture pieces, > need to know if the compiler is building it with the stack protector. > This was done in the arch/Kconfig with 'select', but this doesn't > allow a way to do auto-detected compiler support. In preparation for > creating an on-if-available default, move the logic for the definition of > CONFIG_CC_STACKPROTECTOR into the Makefile. > > Cc: Masahiro Yamada <yamada.masahiro@socionext.com> > Cc: Michal Marek <mmarek@suse.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: Laura Abbott <labbott@redhat.com> > Cc: Nicholas Piggin <npiggin@gmail.com> > Cc: Al Viro <viro@zeniv.linux.org.uk> > Cc: linux-kbuild@vger.kernel.org > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > Makefile | 7 +++++-- > arch/Kconfig | 8 -------- > 2 files changed, 5 insertions(+), 10 deletions(-) > > diff --git a/Makefile b/Makefile > index d1119941261c..e122a9cf0399 100644 > --- a/Makefile > +++ b/Makefile > @@ -688,8 +688,11 @@ else > stackp-flag := $(call cc-option, -fno-stack-protector) > endif > endif > -# Find arch-specific stack protector compiler sanity-checking script. > -ifdef CONFIG_CC_STACKPROTECTOR > +ifdef stackp-name > + # If the stack protector has been selected, inform the rest of the build. > + KBUILD_CFLAGS += -DCONFIG_CC_STACKPROTECTOR > + KBUILD_AFLAGS += -DCONFIG_CC_STACKPROTECTOR > + # Find arch-specific stack protector compiler sanity-checking script. > stackp-path := $(srctree)/scripts/gcc-$(SRCARCH)_$(BITS)-has-stack-protector.sh > stackp-check := $(wildcard $(stackp-path)) > endif
I have not tested this series, but I think this commit is bad (with the follow-up patch applied).
I thought of this scenario:
[1] Kernel is configured with CONFIG_CC_STACKPROTECTOR_AUTO
[2] Kernel is built with a compiler without stack protector support.
[3] CONFIG_CC_STACKPROTECTOR is not defined, so __stack_chk_fail() is not compiled.
[4] Out-of-tree modules are compiled with a compiler with stack protector support. __stack_chk_fail() is inserted to functions of the modules.
[5] insmod fails because reference to __stack_chk_fail() can not be resolved.
I think "select CC_STACKPROTECTOR" should be kept in Kconfig.
-- Best Regards Masahiro Yamada
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