linux-kernel - [PATCH 5.4 007/120] efi/libstub: Disable Shadow Call Stack

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Date:   Mon, 26 Sep 2022 12:10:40 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, James Morse <james.morse@....com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Will Deacon <will@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 007/120] efi/libstub: Disable Shadow Call Stack

From: Sami Tolvanen <samitolvanen@...gle.com>

[ Upstream commit cc49c71d2abe99c1c2c9bedf0693ad2d3ee4a067 ]

Shadow stacks are not available in the EFI stub, filter out SCS flags.

Suggested-by: James Morse <james.morse@....com>
Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
Acked-by: Ard Biesheuvel <ardb@...nel.org>
Signed-off-by: Will Deacon <will@...nel.org>
Stable-dep-of: 1a3887924a7e ("efi: libstub: Disable struct randomization")
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/firmware/efi/libstub/Makefile | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index 8c5b5529dbc0..f3540d5dd276 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -31,6 +31,9 @@ KBUILD_CFLAGS			:= $(cflags-y) -DDISABLE_BRANCH_PROFILING \
 				   $(call cc-option,-fno-addrsig) \
 				   -D__DISABLE_EXPORTS
 
+# remove SCS flags from all objects in this directory
+KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS))
+
 GCOV_PROFILE			:= n
 KASAN_SANITIZE			:= n
 UBSAN_SANITIZE			:= n
-- 
2.35.1