This is a note to let you know that I've just added the patch titled
Makefile: link with -z noexecstack --no-warn-rwx-segments
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
makefile-link-with-z-noexecstack-no-warn-rwx-segments.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 0d362be5b14200b77ecc2127936a5ff82fbffe41 Mon Sep 17 00:00:00 2001
From: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Date: Wed, 10 Aug 2022 15:24:40 -0700
Subject: Makefile: link with -z noexecstack --no-warn-rwx-segments
From: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
commit 0d362be5b14200b77ecc2127936a5ff82fbffe41 upstream.
Users of GNU ld (BFD) from binutils 2.39+ will observe multiple
instances of a new warning when linking kernels in the form:
ld: warning: vmlinux: missing .note.GNU-stack section implies executable stack
ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker
ld: warning: vmlinux has a LOAD segment with RWX permissions
Generally, we would like to avoid the stack being executable. Because
there could be a need for the stack to be executable, assembler sources
have to opt-in to this security feature via explicit creation of the
.note.GNU-stack feature (which compilers create by default) or command
line flag --noexecstack. Or we can simply tell the linker the
production of such sections is irrelevant and to link the stack as
--noexecstack.
LLVM's LLD linker defaults to -z noexecstack, so this flag isn't
strictly necessary when linking with LLD, only BFD, but it doesn't hurt
to be explicit here for all linkers IMO. --no-warn-rwx-segments is
currently BFD specific and only available in the current latest release,
so it's wrapped in an ld-option check.
While the kernel makes extensive usage of ELF sections, it doesn't use
permissions from ELF segments.
Link: https://lore.kernel.org/linux-block/3af4127a-f453-4cf7-f133-a181cce06f73@xxxxxxxxx/
Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=ba951afb99912da01a6e8434126b8fac7aa75107
Link: https://github.com/llvm/llvm-project/issues/57009
Reported-and-tested-by: Jens Axboe <axboe@xxxxxxxxx>
Suggested-by: Fangrui Song <maskray@xxxxxxxxxx>
Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
Makefile | 5 +++++
1 file changed, 5 insertions(+)
--- a/Makefile
+++ b/Makefile
@@ -870,6 +870,11 @@ ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATI
LDFLAGS_vmlinux += $(call ld-option, --gc-sections,)
endif
+KBUILD_LDFLAGS += -z noexecstack
+ifeq ($(CONFIG_LD_IS_BFD),y)
+KBUILD_LDFLAGS += $(call ld-option,--no-warn-rwx-segments)
+endif
+
ifeq ($(CONFIG_STRIP_ASM_SYMS),y)
LDFLAGS_vmlinux += $(call ld-option, -X,)
endif
Patches currently in stable-queue which might be from ndesaulniers@xxxxxxxxxx are
queue-4.9/arm-crypto-comment-out-gcc-warning-that-breaks-clang-builds.patch
queue-4.9/makefile-link-with-z-noexecstack-no-warn-rwx-segments.patch
queue-4.9/x86-link-vdso-and-boot-with-z-noexecstack-no-warn-rwx-segments.patch
