From: Arnd Bergmann arnd@arndb.de Subject: ubsan: build ubsan.c more conservatively

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. According to Andrey Ryabinin, that option is not even needed, dropping it here fixes the stackprotector issue.

Link: http://lkml.kernel.org/r/20190722125139.1335385-1-arnd@arndb.de Link: https://lore.kernel.org/lkml/20190617123109.667090-1-arnd@arndb.de/t/ Link: https://lore.kernel.org/lkml/20190722091050.2188664-1-arnd@arndb.de/t/ Fixes: d08965a27e84 ("x86/uaccess, ubsan: Fix UBSAN vs. SMAP") Signed-off-by: Arnd Bergmann arnd@arndb.de Reviewed-by: Andrey Ryabinin aryabinin@virtuozzo.com Cc: Josh Poimboeuf jpoimboe@redhat.com Cc: Peter Zijlstra peterz@infradead.org Cc: Arnd Bergmann arnd@arndb.de Cc: Borislav Petkov bp@alien8.de Cc: Dmitry Vyukov dvyukov@google.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Ingo Molnar mingo@kernel.org Cc: Kees Cook keescook@chromium.org Cc: Matthew Wilcox willy@infradead.org Cc: Ard Biesheuvel ard.biesheuvel@linaro.org Cc: Andy Shevchenko andriy.shevchenko@linux.intel.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

lib/Makefile | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/lib/Makefile~ubsan-build-ubsanc-more-conservatively +++ a/lib/Makefile @@ -279,7 +279,8 @@ obj-$(CONFIG_UCS2_STRING) += ucs2_string obj-$(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-stack-protector) $(DISABLE_STACKLEAK_PLUGIN)

obj-$(CONFIG_SBITMAP) += sbitmap.o

_