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From: Arnd Bergmann <arnd@kernel.org>
To: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Nathan Chancellor <natechancellor@gmail.com>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Marco Elver <elver@google.com>,
	George Popescu <georgepope@android.com>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com
Subject: [PATCH] ubsan: disable unsigned-integer-overflow sanitizer with clang
Date: Wed, 30 Dec 2020 16:47:35 +0100
Message-ID: <20201230154749.746641-1-arnd@kernel.org> (raw)

From: Arnd Bergmann <arnd@arndb.de>

Building ubsan kernels even for compile-testing introduced these
warnings in my randconfig environment:

crypto/blake2b_generic.c:98:13: error: stack frame size of 9636 bytes in function 'blake2b_compress' [-Werror,-Wframe-larger-than=]
static void blake2b_compress(struct blake2b_state *S,
crypto/sha512_generic.c:151:13: error: stack frame size of 1292 bytes in function 'sha512_generic_block_fn' [-Werror,-Wframe-larger-than=]
static void sha512_generic_block_fn(struct sha512_state *sst, u8 const *src,
lib/crypto/curve25519-fiat32.c:312:22: error: stack frame size of 2180 bytes in function 'fe_mul_impl' [-Werror,-Wframe-larger-than=]
static noinline void fe_mul_impl(u32 out[10], const u32 in1[10], const u32 in2[10])
lib/crypto/curve25519-fiat32.c:444:22: error: stack frame size of 1588 bytes in function 'fe_sqr_impl' [-Werror,-Wframe-larger-than=]
static noinline void fe_sqr_impl(u32 out[10], const u32 in1[10])

Further testing showed that this is caused by
-fsanitize=unsigned-integer-overflow.

The one in blake2b immediately overflows the 8KB stack area on 32-bit
architectures, so better ensure this never happens by making this
option gcc-only.

Fixes: d0a3ac549f38 ("ubsan: enable for all*config builds")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 lib/Kconfig.ubsan | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan
index 8b635fd75fe4..e23873282ba7 100644
--- a/lib/Kconfig.ubsan
+++ b/lib/Kconfig.ubsan
@@ -122,6 +122,8 @@ config UBSAN_SIGNED_OVERFLOW
 
 config UBSAN_UNSIGNED_OVERFLOW
 	bool "Perform checking for unsigned arithmetic overflow"
+	# clang hugely expands stack usage with -fsanitize=object-size
+	depends on !CC_IS_CLANG
 	depends on $(cc-option,-fsanitize=unsigned-integer-overflow)
 	help
 	  This option enables -fsanitize=unsigned-integer-overflow which checks
-- 
2.29.2


             reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-30 15:47 Arnd Bergmann [this message]
2020-12-30 16:13 ` Marco Elver
2021-01-04 22:33   ` Nathan Chancellor
2021-01-04 23:33     ` Andrew Morton
2021-01-04 23:34       ` Nathan Chancellor
2021-01-05  9:25     ` Arnd Bergmann
2021-01-06  9:12       ` Arnd Bergmann
2021-01-06 21:38         ` Nathan Chancellor
2021-01-06 22:06           ` Arnd Bergmann
2021-01-07  3:34             ` Nathan Chancellor
2021-01-06 21:57 ` Kees Cook
2021-01-06 22:12   ` Arnd Bergmann
2021-01-06 23:17     ` Kees Cook
2021-01-06 23:40       ` Arnd Bergmann
2021-01-07 16:09     ` Arnd Bergmann
2021-01-07 17:22       ` Kees Cook
2021-01-07 18:15         ` Nathan Chancellor
2021-01-07 20:41           ` Arnd Bergmann

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