kasan: don't emit builtin calls when sanitization is off

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.git.andreyknvl@google.com
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>
[ Sami: Backported to 4.9 avoiding c5caf21ab0cf8 and e7c52b84fb ]
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/Makefile b/Makefile
index fea2fe577185bd50a30d4464098c042a6d88bde9..62fbcc04bf70f51b1e23454aed2b449454e32bb5 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -417,7 +417,8 @@ 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_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 37323b0df374b1a89fb256a4077165bc05376421..2624d4bf9a4542be4f4d312fe029b47553d90805 100644 (file)
--- 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 ae0f9ab1a70d995f8ec2612ef8ceb669507b5c54..c954040c3cf2f16141698681b5af9a33f7bb6bb6 100644 (file)
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -127,7 +127,7 @@ 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)