From: Andrey Konovalov andreyknvl@google.com

commit 0e410e158e5baa1300bdf678cea4f4e0cf9d8b94 upstream.

With KASAN enabled the kernel has two different memset() functions, one with KASAN checks (memset) and one without (__memset). KASAN uses some macro tricks to use the proper version where required. For example memset() calls in mm/slub.c are without KASAN checks, since they operate on poisoned slab object metadata.

The issue is that clang emits memset() calls even when there is no memset() in the source code. They get linked with improper memset() implementation and the kernel fails to boot due to a huge amount of KASAN reports during early boot stages.

The solution is to add -fno-builtin flag for files with KASAN_SANITIZE := n marker.

Link: http://lkml.kernel.org/r/8ffecfffe04088c52c42b92739c2bd8a0bcb3f5e.1516384594... Signed-off-by: Andrey Konovalov andreyknvl@google.com Acked-by: Nick Desaulniers ndesaulniers@google.com Cc: Masahiro Yamada yamada.masahiro@socionext.com Cc: Michal Marek michal.lkml@markovi.net Cc: Andrey Ryabinin aryabinin@virtuozzo.com Cc: Alexander Potapenko glider@google.com Cc: Dmitry Vyukov dvyukov@google.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org [ Nick : Backported to 4.4 avoiding KUBSAN ] Signed-off-by: Nick Desaulniers ndesaulniers@google.com --- Makefile | 3 ++- scripts/Makefile.kasan | 3 +++ scripts/Makefile.lib | 2 +- 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile index ee92a12e3a4b..4fdd43dd14aa 100644 --- a/Makefile +++ b/Makefile @@ -418,7 +418,8 @@ export MAKE AWK GENKSYMS INSTALLKERNEL PERL PYTHON UTS_MACHINE export HOSTCXX HOSTCXXFLAGS LDFLAGS_MODULE CHECK CHECKFLAGS

export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS LDFLAGS -export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE CFLAGS_GCOV CFLAGS_KASAN +export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE CFLAGS_GCOV +export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE export KBUILD_AFLAGS AFLAGS_KERNEL AFLAGS_MODULE export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_LDFLAGS_MODULE export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan index 37323b0df374..2624d4bf9a45 100644 --- a/scripts/Makefile.kasan +++ b/scripts/Makefile.kasan @@ -28,4 +28,7 @@ else CFLAGS_KASAN := $(CFLAGS_KASAN_MINIMAL) endif endif + +CFLAGS_KASAN_NOSANITIZE := -fno-builtin + endif diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index 24914e7de944..a2d0e6d32659 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -126,7 +126,7 @@ endif ifeq ($(CONFIG_KASAN),y) _c_flags += $(if $(patsubst n%,, \ $(KASAN_SANITIZE_$(basetarget).o)$(KASAN_SANITIZE)y), \ - $(CFLAGS_KASAN)) + $(CFLAGS_KASAN), $(CFLAGS_KASAN_NOSANITIZE)) endif

# If building the kernel in a separate objtree expand all occurrences