This is a note to let you know that I've just added the patch titled
x86: link vdso and boot 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:
x86-link-vdso-and-boot-with-z-noexecstack-no-warn-rw.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.
commit 48743dd7af756c78525a20ebeb0fa2aaa3ad56af
Author: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Date: Wed Aug 10 15:24:41 2022 -0700
x86: link vdso and boot with -z noexecstack --no-warn-rwx-segments
commit ffcf9c5700e49c0aee42dcba9a12ba21338e8136 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: arch/x86/boot/pmjump.o: 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: arch/x86/boot/compressed/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>
diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile
index d1df7d2e31b1..ffa96111eacc 100644
--- a/arch/x86/boot/Makefile
+++ b/arch/x86/boot/Makefile
@@ -100,7 +100,7 @@ $(obj)/zoffset.h: $(obj)/compressed/vmlinux FORCE
AFLAGS_header.o += -I$(objtree)/$(obj)
$(obj)/header.o: $(obj)/zoffset.h
-LDFLAGS_setup.elf := -m elf_i386 -T
+LDFLAGS_setup.elf := -m elf_i386 -z noexecstack -T
$(obj)/setup.elf: $(src)/setup.ld $(SETUP_OBJS) FORCE
$(call if_changed,ld)
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 7be7acd6a540..3985eb76d12a 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -54,6 +54,12 @@ else
LDFLAGS += $(shell $(LD) --help 2>&1 | grep -q "\-z noreloc-overflow" \
&& echo "-z noreloc-overflow -pie --no-dynamic-linker")
endif
+
+LDFLAGS += -z noexecstack
+ifeq ($(CONFIG_LD_IS_BFD),y)
+LDFLAGS += $(call ld-option,--no-warn-rwx-segments)
+endif
+
LDFLAGS_vmlinux := -T
hostprogs-y := mkpiggy
diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index 0d3ebdfa0739..99597d3648f3 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -168,7 +168,7 @@ quiet_cmd_vdso = VDSO $@
VDSO_LDFLAGS = -shared $(call ld-option, --hash-style=both) \
$(call ld-option, --build-id) $(call ld-option, --eh-frame-hdr) \
- -Bsymbolic
+ -Bsymbolic -z noexecstack
GCOV_PROFILE := n
#
