On 7/22/19 12:10 PM, Arnd Bergmann wrote:
> objtool points out several conditions that it does not like, depending
> on the combination with other configuration options and compiler
> variants:
>
> stack protector:
> lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch()+0xbf: call to
> __stack_chk_fail() with UACCESS enabled
> lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch_v1()+0xbe: call
> to __stack_chk_fail() with UACCESS enabled
>
> stackleak plugin:
> lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch()+0x4a: call to
> stackleak_track_stack() with UACCESS enabled
> lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch_v1()+0x4a: call
> to stackleak_track_stack() with UACCESS enabled
>
> kasan:
> lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch()+0x25: call to
> memcpy() with UACCESS enabled
> lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch_v1()+0x25: call
> to memcpy() with UACCESS enabled
>
> The stackleak and kasan options just need to be disabled for this file
> as we do for other files already. For the stack protector, we already
> attempt to disable it, but this fails on clang because the check is
> mixed with the gcc specific -fno-conserve-stack option, so we need to
> test them separately.
>
> Fixes: 42440c1f9911 ("lib/ubsan: add type mismatch handler for new GCC/Clang")
There was no uaccess validataion at that time, so the right fixes line is
probably this:
Fixes: d08965a27e84 ("x86/uaccess, ubsan: Fix UBSAN vs. SMAP")
> Link: https://lore.kernel.org/lkml/20190617123109.667090-1-a...@arndb.de/t/
> Cc: sta...@vger.kernel.org
> Signed-off-by: Arnd Bergmann <a...@arndb.de>
> ---
> lib/Makefile | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/lib/Makefile b/lib/Makefile
> index 095601ce371d..320e3b632dd3 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -279,7 +279,8 @@ obj-$(CONFIG_UCS2_STRING) += ucs2_string.o
> obj-$(CONFIG_UBSAN) += ubsan.o
>
> UBSAN_SANITIZE_ubsan.o := n
> -CFLAGS_ubsan.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
> +KASAN_SANITIZE_ubsan.o := n
> +CFLAGS_ubsan.o := $(call cc-option, -fno-conserve-stack) $(call cc-option,
> -fno-stack-protector) $(DISABLE_STACKLEAK_PLUGIN)
$(call cc-option, -fno-conserve-stack) can be removed entirely. It's just copy
paste from kasan Makefile.
It was added in kasan purely for performance reasons.
Not sure that it's needed even in kasan Makefile, the code which was
the reason for adding fno-conserve-stack might not get into the final version
of KASAN patches.
