From: Kees Cook Date: Sat, 26 Jul 2025 06:44:26 +0000 (-0700) Subject: kstack_erase: Disable kstack_erase for all of arm compressed boot code X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=431a380f935e2c74cbaeac65367c70fc18903315;p=thirdparty%2Fkernel%2Flinux.git kstack_erase: Disable kstack_erase for all of arm compressed boot code When building with CONFIG_KSTACK_ERASE=y and CONFIG_ARM_ATAG_DTB_COMPAT=y, the compressed boot environment encounters an undefined symbol error: ld.lld: error: undefined symbol: __sanitizer_cov_stack_depth >>> referenced by atags_to_fdt.c:135 This occurs because the compiler instruments the atags_to_fdt() function with sanitizer coverage calls, but the minimal compressed boot environment lacks access to sanitizer runtime support. The compressed boot environment already disables stack protector with -fno-stack-protector. Similarly disable sanitizer coverage by adding $(DISABLE_KSTACK_ERASE) to the general compiler flags (and remove it from the one place it was noticed before), which contains the appropriate flags to prevent sanitizer instrumentation. This follows the same pattern used in other early boot contexts where sanitizer runtime support is unavailable. Reported-by: Linux Kernel Functional Testing Closes: https://lore.kernel.org/all/CA+G9fYtBk8qnpWvoaFwymCx5s5i-5KXtPGpmf=_+UKJddCOnLA@mail.gmail.com Reported-by: Nathan Chancellor Closes: https://lore.kernel.org/all/20250726004313.GA3650901@ax162 Suggested-by: Nathan Chancellor Tested-by: Nathan Chancellor Signed-off-by: Kees Cook --- diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile index f9075edfd773a..a159120d1e42e 100644 --- a/arch/arm/boot/compressed/Makefile +++ b/arch/arm/boot/compressed/Makefile @@ -9,7 +9,6 @@ OBJS = HEAD = head.o OBJS += misc.o decompress.o -CFLAGS_decompress.o += $(DISABLE_KSTACK_ERASE) ifeq ($(CONFIG_DEBUG_UNCOMPRESS),y) OBJS += debug.o AFLAGS_head.o += -DDEBUG @@ -96,6 +95,7 @@ KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING ccflags-y := -fpic $(call cc-option,-mno-single-pic-base,) -fno-builtin \ -I$(srctree)/scripts/dtc/libfdt -fno-stack-protector \ + $(DISABLE_KSTACK_ERASE) \ -I$(obj) ccflags-remove-$(CONFIG_FUNCTION_TRACER) += -pg asflags-y := -DZIMAGE