From 4ce1e94175696b8f5f6fa29f09f7ef56724ddc2a Mon Sep 17 00:00:00 2001
From: Kees Cook <keescook@chromium.org>
Date: Tue, 30 May 2023 17:34:15 -0700
Subject: [PATCH] s390/purgatory: Do not use fortified string functions
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With the addition of -fstrict-flex-arrays=3, struct sha256_state's
trailing array is no longer ignored by CONFIG_FORTIFY_SOURCE:
struct sha256_state {
u32 state[SHA256_DIGEST_SIZE / 4];
u64 count;
u8 buf[SHA256_BLOCK_SIZE];
};
This means that the memcpy() calls with "buf" as a destination in
sha256.c's code will attempt to perform run-time bounds checking, which
could lead to calling missing functions, specifically a potential
WARN_ONCE, which isn't callable from purgatory.
Reported-by: Thorsten Leemhuis <linux@leemhuis.info>
Closes: https://lore.kernel.org/lkml/175578ec-9dec-7a9c-8d3a-43f24ff86b92@leemhuis.info/
Bisected-by: "Joan Bruguera Micó" <joanbrugueram@gmail.com>
Fixes: df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3")
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Linux Kernel Functional Testing <lkft@linaro.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: linux-s390@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20230531003414.never.050-kees@kernel.org
---
arch/s390/purgatory/Makefile | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/s390/purgatory/Makefile b/arch/s390/purgatory/Makefile
index 32573b4f9bd20..cf14740abd1c7 100644
--- a/arch/s390/purgatory/Makefile
+++ b/arch/s390/purgatory/Makefile
@@ -10,7 +10,7 @@ PURGATORY_OBJS = $(addprefix $(obj)/,$(purgatory-y))
$(obj)/sha256.o: $(srctree)/lib/crypto/sha256.c FORCE
$(call if_changed_rule,cc_o_c)
-CFLAGS_sha256.o := -D__DISABLE_EXPORTS
+CFLAGS_sha256.o := -D__DISABLE_EXPORTS -D__NO_FORTIFY
$(obj)/mem.o: $(srctree)/arch/s390/lib/mem.S FORCE
$(call if_changed_rule,as_o_S)
--
2.30.2