From: Kees Cook <keescook@chromium.org>
To: Paul Walmsley <paul.walmsley@sifive.com>
Cc: "Kees Cook" <keescook@chromium.org>,
"Thorsten Leemhuis" <linux@leemhuis.info>,
"Joan Bruguera Micó" <joanbrugueram@gmail.com>,
"Palmer Dabbelt" <palmer@dabbelt.com>,
"Albert Ou" <aou@eecs.berkeley.edu>,
"Masahiro Yamada" <masahiroy@kernel.org>,
"Conor Dooley" <conor.dooley@microchip.com>,
"Nick Desaulniers" <ndesaulniers@google.com>,
"Alyssa Ross" <hi@alyssa.is>,
"Heiko Stuebner" <heiko.stuebner@vrull.eu>,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
linux-riscv@lists.infradead.org,
"Andrew Jones" <ajones@ventanamicro.com>,
linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: [PATCH v2] riscv/purgatory: Do not use fortified string functions
Date: Thu, 1 Jun 2023 09:00:28 -0700 [thread overview]
Message-ID: <20230601160025.gonna.868-kees@kernel.org> (raw)
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: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Conor Dooley <conor.dooley@microchip.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Alyssa Ross <hi@alyssa.is>
Cc: Heiko Stuebner <heiko.stuebner@vrull.eu>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: linux-riscv@lists.infradead.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
v2: - only limit fortify for sha256 (conor)
v1: https://lore.kernel.org/lkml/20230531003404.never.167-kees@kernel.org
---
arch/riscv/purgatory/Makefile | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/riscv/purgatory/Makefile b/arch/riscv/purgatory/Makefile
index 5730797a6b40..8c73360c42bb 100644
--- a/arch/riscv/purgatory/Makefile
+++ b/arch/riscv/purgatory/Makefile
@@ -31,7 +31,7 @@ $(obj)/strncmp.o: $(srctree)/arch/riscv/lib/strncmp.S FORCE
$(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
CFLAGS_string.o := -D__DISABLE_EXPORTS
CFLAGS_ctype.o := -D__DISABLE_EXPORTS
--
2.34.1
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next reply other threads:[~2023-06-01 16:00 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-01 16:00 Kees Cook [this message]
2023-06-01 17:34 ` [PATCH v2] riscv/purgatory: Do not use fortified string functions Conor Dooley
2023-06-01 18:27 ` Kees Cook
2023-06-01 20:17 ` Palmer Dabbelt
2023-06-01 20:31 ` Kees Cook
2023-06-01 21:04 ` Palmer Dabbelt
2023-06-01 20:20 ` patchwork-bot+linux-riscv
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