+ kasan-fix-gcc-mem-intrinsic-prefix-with-sw-tags.patch added to mm-hotfixes-unstable branch

+ kasan-fix-gcc-mem-intrinsic-prefix-with-sw-tags.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: kasan: fix GCC mem-intrinsic prefix with sw tags
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     kasan-fix-gcc-mem-intrinsic-prefix-with-sw-tags.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kasan-fix-gcc-mem-intrinsic-prefix-with-sw-tags.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Ada Couprie Diaz <ada.coupriediaz@arm.com>
Subject: kasan: fix GCC mem-intrinsic prefix with sw tags
Date: Thu, 21 Aug 2025 13:07:35 +0100

GCC doesn't support "hwasan-kernel-mem-intrinsic-prefix", only
"asan-kernel-mem-intrinsic-prefix"[0], while LLVM supports both.  This is
already taken into account when checking
"CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX", but not in the KASAN Makefile
adding those parameters when "CONFIG_KASAN_SW_TAGS" is enabled.

Replace the version check with "CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX",
which already validates that mem-intrinsic prefix parameter can be used,
and choose the correct name depending on compiler.

GCC 13 and above trigger "CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX" which
prevents `mem{cpy,move,set}()` being redefined in "mm/kasan/shadow.c"
since commit 36be5cba99f6 ("kasan: treat meminstrinsic as builtins in
uninstrumented files"), as we expect the compiler to prefix those calls
with `__(hw)asan_` instead.  But as the option passed to GCC has been
incorrect, the compiler has not been emitting those prefixes, effectively
never calling the instrumented versions of `mem{cpy,move,set}()` with
"CONFIG_KASAN_SW_TAGS" enabled.

If "CONFIG_FORTIFY_SOURCES" is enabled, this issue would be mitigated as
it redefines `mem{cpy,move,set}()` and properly aliases the
`__underlying_mem*()` that will be called to the instrumented versions.

[0]: https://gcc.gnu.org/onlinedocs/gcc-13.4.0/gcc/Optimize-Options.html

Link: https://lkml.kernel.org/r/20250821120735.156244-1-ada.coupriediaz@arm.com
Signed-off-by: Ada Couprie Diaz <ada.coupriediaz@arm.com>
Fixes: 36be5cba99f6 ("kasan: treat meminstrinsic as builtins in uninstrumented files")
Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 scripts/Makefile.kasan |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

--- a/scripts/Makefile.kasan~kasan-fix-gcc-mem-intrinsic-prefix-with-sw-tags
+++ a/scripts/Makefile.kasan
@@ -86,10 +86,14 @@ kasan_params += hwasan-instrument-stack=
 		hwasan-use-short-granules=0 \
 		hwasan-inline-all-checks=0
 
-# Instrument memcpy/memset/memmove calls by using instrumented __hwasan_mem*().
-ifeq ($(call clang-min-version, 150000)$(call gcc-min-version, 130000),y)
-	kasan_params += hwasan-kernel-mem-intrinsic-prefix=1
-endif
+# Instrument memcpy/memset/memmove calls by using instrumented __(hw)asan_mem*().
+ifdef CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX
+	ifdef CONFIG_CC_IS_GCC
+		kasan_params += asan-kernel-mem-intrinsic-prefix=1
+	else
+		kasan_params += hwasan-kernel-mem-intrinsic-prefix=1
+	endif
+endif # CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX
 
 endif # CONFIG_KASAN_SW_TAGS
 
_

Patches currently in -mm which might be from ada.coupriediaz@arm.com are

kasan-fix-gcc-mem-intrinsic-prefix-with-sw-tags.patch