6.6-stable review patch. If anyone has any objections, please let me know.
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From: Nathan Chancellor nathan@kernel.org
commit 2f13daee2a72bb962f5fd356c3a263a6f16da965 upstream.
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-... Signed-off-by: Eric Biggers ebiggers@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- lib/crypto/Makefile | 4 ++++ 1 file changed, 4 insertions(+)
--- a/lib/crypto/Makefile +++ b/lib/crypto/Makefile @@ -30,6 +30,10 @@ obj-$(CONFIG_CRYPTO_LIB_CURVE25519_GENER libcurve25519-generic-y := curve25519-fiat32.o libcurve25519-generic-$(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