linux-hardening - [PATCH v5 07/27] x86/build: Check W^X of vmlinux during build

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Date:   Tue, 14 Mar 2023 13:13:34 +0300
From:   Evgeniy Baskov <baskov@...ras.ru>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Evgeniy Baskov <baskov@...ras.ru>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexey Khoroshilov <khoroshilov@...ras.ru>,
        Peter Jones <pjones@...hat.com>,
        Gerd Hoffmann <kraxel@...hat.com>,
        "Limonciello, Mario" <mario.limonciello@....com>,
        joeyli <jlee@...e.com>, lvc-project@...uxtesting.org,
        x86@...nel.org, linux-efi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH v5 07/27] x86/build: Check W^X of vmlinux during build

Check if there are simultaneously writable and executable
program segments in vmlinux ELF image and fail build if there are any.

This would prevent accidental introduction of RWX segments.

Tested-by: Mario Limonciello <mario.limonciello@....com>
Signed-off-by: Evgeniy Baskov <baskov@...ras.ru>
---
 arch/x86/boot/compressed/Makefile | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 6b6cfe607bdb..0c6e25279ec1 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -112,12 +112,17 @@ vmlinux-objs-$(CONFIG_EFI) += $(obj)/efi.o
 vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_mixed.o
 vmlinux-objs-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a
 
+quiet_cmd_objcopy_and_wx_check = $(quiet_cmd_objcopy)
+cmd_objcopy_and_wx_check = if $(OBJDUMP) -p $< | grep "flags .wx" > /dev/null; then \
+				   (echo >&2 "$<: Simultaneously writable and executable sections are prohibited"; \
+				    /bin/false); else $(cmd_objcopy); fi
+
 $(obj)/vmlinux: $(vmlinux-objs-y) FORCE
 	$(call if_changed,ld)
 
 OBJCOPYFLAGS_vmlinux.bin :=  -R .comment -S
 $(obj)/vmlinux.bin: vmlinux FORCE
-	$(call if_changed,objcopy)
+	$(call if_changed,objcopy_and_wx_check)
 
 targets += $(patsubst $(obj)/%,%,$(vmlinux-objs-y)) vmlinux.bin.all vmlinux.relocs
 
-- 
2.39.2