The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 0e410e158e5baa1300bdf678cea4f4e0cf9d8b94 Mon Sep 17 00:00:00 2001

From: Andrey Konovalov andreyknvl@google.com Date: Tue, 6 Feb 2018 15:36:00 -0800 Subject: [PATCH] kasan: don't emit builtin calls when sanitization is off

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

diff --git a/Makefile b/Makefile index 11aff0f9e105..0d49ff4022fb 100644 --- a/Makefile +++ b/Makefile @@ -434,7 +434,8 @@ export MAKE LEX YACC 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_KASAN CFLAGS_UBSAN +export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE +export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE CFLAGS_UBSAN 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 1ce7115aa499..94c9e65cc83a 100644 --- a/scripts/Makefile.kasan +++ b/scripts/Makefile.kasan @@ -31,4 +31,7 @@ else endif

CFLAGS_KASAN += $(call cc-option, -fsanitize-address-use-after-scope) + +CFLAGS_KASAN_NOSANITIZE := -fno-builtin + endif diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index 5fdc1a19b02c..5589bae34af6 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -121,7 +121,7 @@ endif ifeq ($(CONFIG_KASAN),y) _c_flags += $(if $(patsubst n%,, \ $(KASAN_SANITIZE_$(basetarget).o)$(KASAN_SANITIZE)y), \ - $(CFLAGS_KASAN)) + $(CFLAGS_KASAN), $(CFLAGS_KASAN_NOSANITIZE)) endif

ifeq ($(CONFIG_UBSAN),y)