diff options
| author | Nathan Chancellor <nathan@kernel.org> | 2025-06-09 15:45:20 -0700 |
|---|---|---|
| committer | Eric Biggers <ebiggers@google.com> | 2025-06-15 18:14:54 -0700 |
| commit | 2f13daee2a72bb962f5fd356c3a263a6f16da965 (patch) | |
| tree | f3415720a2d9e396fd9b296024da25c2654e13e9 /lib/crypto | |
| parent | e202196b8aa249d78ab87eae56bbe0e71e3dc39c (diff) | |
lib/crypto/curve25519-hacl64: Disable KASAN with clang-17 and older
After commit 6f110a5e4f99 ("Disable SLUB_TINY for build testing"), which
causes CONFIG_KASAN to be enabled in allmodconfig again, arm64
allmodconfig builds with clang-17 and older show an instance of
-Wframe-larger-than (which breaks the build with CONFIG_WERROR=y):
lib/crypto/curve25519-hacl64.c:757:6: error: stack frame size (2336) exceeds limit (2048) in 'curve25519_generic' [-Werror,-Wframe-larger-than]
757 | void curve25519_generic(u8 mypublic[CURVE25519_KEY_SIZE],
| ^
When KASAN is disabled, the stack usage is roughly quartered:
lib/crypto/curve25519-hacl64.c:757:6: error: stack frame size (608) exceeds limit (128) in 'curve25519_generic' [-Werror,-Wframe-larger-than]
757 | void curve25519_generic(u8 mypublic[CURVE25519_KEY_SIZE],
| ^
Using '-Rpass-analysis=stack-frame-layout' shows the following variables
and many, many 8-byte spills when KASAN is enabled:
Offset: [SP-144], Type: Variable, Align: 8, Size: 40
Offset: [SP-464], Type: Variable, Align: 8, Size: 320
Offset: [SP-784], Type: Variable, Align: 8, Size: 320
Offset: [SP-864], Type: Variable, Align: 32, Size: 80
Offset: [SP-896], Type: Variable, Align: 32, Size: 32
Offset: [SP-1016], Type: Variable, Align: 8, Size: 120
When KASAN is disabled, there are still spills but not at many and the
variables list is smaller:
Offset: [SP-192], Type: Variable, Align: 32, Size: 80
Offset: [SP-224], Type: Variable, Align: 32, Size: 32
Offset: [SP-344], Type: Variable, Align: 8, Size: 120
Disable KASAN for this file when using clang-17 or older to avoid
blowing out the stack, clearing up the warning.
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: "Jason A. Donenfeld" <Jason@zx2c4.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250609-curve25519-hacl64-disable-kasan-clang-v1-1-08ea0ac5ccff@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Diffstat (limited to 'lib/crypto')
| -rw-r--r-- | lib/crypto/Makefile | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/lib/crypto/Makefile b/lib/crypto/Makefile index 3e79283b617d9..18664127ecd66 100644 --- a/lib/crypto/Makefile +++ b/lib/crypto/Makefile @@ -35,6 +35,10 @@ obj-$(CONFIG_CRYPTO_LIB_CURVE25519_GENERIC) += libcurve25519-generic.o libcurve25519-generic-y := curve25519-fiat32.o libcurve25519-generic-$(CONFIG_ARCH_SUPPORTS_INT128) := curve25519-hacl64.o libcurve25519-generic-y += curve25519-generic.o +# clang versions prior to 18 may blow out the stack with KASAN +ifeq ($(call clang-min-version, 180000),) +KASAN_SANITIZE_curve25519-hacl64.o := n +endif obj-$(CONFIG_CRYPTO_LIB_CURVE25519) += libcurve25519.o libcurve25519-y += curve25519.o |