* [PATCH] crypto: lib/curve25519-hacl64 - Disable KASAN with clang-17 and older
@ 2025-06-09 22:45 Nathan Chancellor
2025-06-10 9:42 ` Ard Biesheuvel
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Nathan Chancellor @ 2025-06-09 22:45 UTC (permalink / raw)
To: Eric Biggers, Jason A. Donenfeld, Ard Biesheuvel
Cc: linux-crypto, llvm, patches, Nathan Chancellor
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>
---
lib/crypto/Makefile | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/lib/crypto/Makefile b/lib/crypto/Makefile
index 3e79283b617d..18664127ecd6 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
---
base-commit: 19272b37aa4f83ca52bdf9c16d5d81bdd1354494
change-id: 20250609-curve25519-hacl64-disable-kasan-clang-faf6e97315e4
Best regards,
--
Nathan Chancellor <nathan@kernel.org>
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] crypto: lib/curve25519-hacl64 - Disable KASAN with clang-17 and older
2025-06-09 22:45 [PATCH] crypto: lib/curve25519-hacl64 - Disable KASAN with clang-17 and older Nathan Chancellor
@ 2025-06-10 9:42 ` Ard Biesheuvel
2025-06-10 17:41 ` Jason A. Donenfeld
2025-06-10 18:42 ` Eric Biggers
2 siblings, 0 replies; 4+ messages in thread
From: Ard Biesheuvel @ 2025-06-10 9:42 UTC (permalink / raw)
To: Nathan Chancellor
Cc: Eric Biggers, Jason A. Donenfeld, linux-crypto, llvm, patches
On Tue, 10 Jun 2025 at 00:45, Nathan Chancellor <nathan@kernel.org> wrote:
>
> 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: Ard Biesheuvel <ardb@kernel.org>
> ---
> lib/crypto/Makefile | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/lib/crypto/Makefile b/lib/crypto/Makefile
> index 3e79283b617d..18664127ecd6 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
>
> ---
> base-commit: 19272b37aa4f83ca52bdf9c16d5d81bdd1354494
> change-id: 20250609-curve25519-hacl64-disable-kasan-clang-faf6e97315e4
>
> Best regards,
> --
> Nathan Chancellor <nathan@kernel.org>
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] crypto: lib/curve25519-hacl64 - Disable KASAN with clang-17 and older
2025-06-09 22:45 [PATCH] crypto: lib/curve25519-hacl64 - Disable KASAN with clang-17 and older Nathan Chancellor
2025-06-10 9:42 ` Ard Biesheuvel
@ 2025-06-10 17:41 ` Jason A. Donenfeld
2025-06-10 18:42 ` Eric Biggers
2 siblings, 0 replies; 4+ messages in thread
From: Jason A. Donenfeld @ 2025-06-10 17:41 UTC (permalink / raw)
To: Nathan Chancellor
Cc: Eric Biggers, Ard Biesheuvel, linux-crypto, llvm, patches
On Mon, Jun 09, 2025 at 03:45:20PM -0700, Nathan Chancellor wrote:
> 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>
> ---
> lib/crypto/Makefile | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/lib/crypto/Makefile b/lib/crypto/Makefile
> index 3e79283b617d..18664127ecd6 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
Seems reasonable. We've had a hassle with this for a while.
Acked-by: Jason A. Donenfeld <Jason@zx2c4.com>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] crypto: lib/curve25519-hacl64 - Disable KASAN with clang-17 and older
2025-06-09 22:45 [PATCH] crypto: lib/curve25519-hacl64 - Disable KASAN with clang-17 and older Nathan Chancellor
2025-06-10 9:42 ` Ard Biesheuvel
2025-06-10 17:41 ` Jason A. Donenfeld
@ 2025-06-10 18:42 ` Eric Biggers
2 siblings, 0 replies; 4+ messages in thread
From: Eric Biggers @ 2025-06-10 18:42 UTC (permalink / raw)
To: Nathan Chancellor
Cc: Jason A. Donenfeld, Ard Biesheuvel, linux-crypto, llvm, patches
On Mon, Jun 09, 2025 at 03:45:20PM -0700, Nathan Chancellor wrote:
> 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>
> ---
> lib/crypto/Makefile | 4 ++++
> 1 file changed, 4 insertions(+)
>
Applied to https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git/log/?h=libcrypto-fixes
Thanks!
- Eric
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2025-06-10 18:43 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-06-09 22:45 [PATCH] crypto: lib/curve25519-hacl64 - Disable KASAN with clang-17 and older Nathan Chancellor
2025-06-10 9:42 ` Ard Biesheuvel
2025-06-10 17:41 ` Jason A. Donenfeld
2025-06-10 18:42 ` Eric Biggers
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).