[PATCH 6.12] lib/crypto: arm/curve25519: Disable on CPU_BIG_ENDIAN

[PATCH 6.12] lib/crypto: arm/curve25519: Disable on CPU_BIG_ENDIAN

[Eric Biggers]

commit 44e8241c51f762aafa50ed116da68fd6ecdcc954 upstream.

On big endian arm kernels, the arm optimized Curve25519 code produces
incorrect outputs and fails the Curve25519 test.  This has been true
ever since this code was added.

It seems that hardly anyone (or even no one?) actually uses big endian
arm kernels.  But as long as they're ostensibly supported, we should
disable this code on them so that it's not accidentally used.

Note: for future-proofing, use !CPU_BIG_ENDIAN instead of
CPU_LITTLE_ENDIAN.  Both of these are arch-specific options that could
get removed in the future if big endian support gets dropped.

Fixes: d8f1308a025f ("crypto: arm/curve25519 - wire up NEON implementation")
Cc: stable@vger.kernel.org
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20251104054906.716914-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
---
 arch/arm/crypto/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/crypto/Kconfig b/arch/arm/crypto/Kconfig
index f87e63b2212e..df2ae5c6af95 100644
--- a/arch/arm/crypto/Kconfig
+++ b/arch/arm/crypto/Kconfig
@@ -2,11 +2,11 @@
 
 menu "Accelerated Cryptographic Algorithms for CPU (arm)"
 
 config CRYPTO_CURVE25519_NEON
 	tristate
-	depends on KERNEL_MODE_NEON
+	depends on KERNEL_MODE_NEON && !CPU_BIG_ENDIAN
 	select CRYPTO_KPP
 	select CRYPTO_LIB_CURVE25519_GENERIC
 	select CRYPTO_ARCH_HAVE_LIB_CURVE25519
 	default CRYPTO_LIB_CURVE25519_INTERNAL
 	help

base-commit: 8a243ecde1f6447b8e237f2c1c67c0bb67d16d67
-- 
2.51.2

Re: [PATCH 6.12] lib/crypto: arm/curve25519: Disable on CPU_BIG_ENDIAN

[Sasha Levin]

Subject: lib/crypto: arm/curve25519: Disable on CPU_BIG_ENDIAN

Thanks!

Re: [PATCH 6.12] lib/crypto: arm/curve25519: Disable on CPU_BIG_ENDIAN

[Eric Biggers]

On Sun, Nov 16, 2025 at 12:19:42PM -0500, Sasha Levin wrote:
> Subject: lib/crypto: arm/curve25519: Disable on CPU_BIG_ENDIAN
> 
> Thanks!

I assume that you meant to write something meaningful in this message.
Also, you forgot to include all the original recipients in Cc.

- Eric

Re: [PATCH 6.12] lib/crypto: arm/curve25519: Disable on CPU_BIG_ENDIAN

[Sasha Levin]

On Sun, Nov 16, 2025 at 11:42:24AM -0800, Eric Biggers wrote:
>On Sun, Nov 16, 2025 at 12:19:42PM -0500, Sasha Levin wrote:
>> Subject: lib/crypto: arm/curve25519: Disable on CPU_BIG_ENDIAN
>>
>> Thanks!
>
>I assume that you meant to write something meaningful in this message.

What else did you expect to see here?

>Also, you forgot to include all the original recipients in Cc.

Yes! I'm trying to automate this workflow, and this is one of the issues I've
fixes with the scripts.

-- 
Thanks,
Sasha

Re: [PATCH 6.12] lib/crypto: arm/curve25519: Disable on CPU_BIG_ENDIAN

[Eric Biggers]

On Sun, Nov 16, 2025 at 07:42:34PM -0500, Sasha Levin wrote:
> On Sun, Nov 16, 2025 at 11:42:24AM -0800, Eric Biggers wrote:
> > On Sun, Nov 16, 2025 at 12:19:42PM -0500, Sasha Levin wrote:
> > > Subject: lib/crypto: arm/curve25519: Disable on CPU_BIG_ENDIAN
> > > 
> > > Thanks!
> > 
> > I assume that you meant to write something meaningful in this message.
> 
> What else did you expect to see here?

Maybe some actual information that wasn't already in the email that
you're replying to?  What are you trying to accomplish?

- Eric

Re: [PATCH 6.12] lib/crypto: arm/curve25519: Disable on CPU_BIG_ENDIAN

[Sasha Levin]

On Sun, Nov 16, 2025 at 05:25:13PM -0800, Eric Biggers wrote:
>On Sun, Nov 16, 2025 at 07:42:34PM -0500, Sasha Levin wrote:
>> On Sun, Nov 16, 2025 at 11:42:24AM -0800, Eric Biggers wrote:
>> > On Sun, Nov 16, 2025 at 12:19:42PM -0500, Sasha Levin wrote:
>> > > Subject: lib/crypto: arm/curve25519: Disable on CPU_BIG_ENDIAN
>> > >
>> > > Thanks!
>> >
>> > I assume that you meant to write something meaningful in this message.
>>
>> What else did you expect to see here?
>
>Maybe some actual information that wasn't already in the email that
>you're replying to?  What are you trying to accomplish?

Letting you know that your backport was queued up?

"b4 ty"?

Do you want a pretty ascii art here?

   _____                                   _                                          _                _                     _   _ 
  |_   _|                                 | |                                        | |              | |                   | | | |
    | |     __ _ _   _  ___ _   _  ___  __| |  _   _ _ __    _   _  ___  _   _ _ __  | |__   __ _  ___| | ___ __   ___  _ __| |_| |
    | |    / _` | | | |/ _ \ | | |/ _ \/ _` | | | | | '_ \  | | | |/ _ \| | | | '__| | '_ \ / _` |/ __| |/ / '_ \ / _ \| '__| __| |
   _| |_  | (_| | |_| |  __/ |_| |  __/ (_| | | |_| | |_) | | |_| | (_) | |_| | |    | |_) | (_| | (__|   <| |_) | (_) | |  | |_|_|
  |_____|  \__, |\__,_|\___|\__,_|\___|\__,_|  \__,_| .__/   \__, |\___/ \__,_|_|    |_.__/ \__,_|\___|_|\_\ .__/ \___/|_|   \__(_)
              | |                                   | |       __/ |                                        | |                     
              |_|                                   |_|      |___/                                         |_|                     

-- 
Thanks,
Sasha

Re: [PATCH 6.12] lib/crypto: arm/curve25519: Disable on CPU_BIG_ENDIAN

[Eric Biggers]

On Sun, Nov 16, 2025 at 08:43:12PM -0500, Sasha Levin wrote:
> On Sun, Nov 16, 2025 at 05:25:13PM -0800, Eric Biggers wrote:
> > On Sun, Nov 16, 2025 at 07:42:34PM -0500, Sasha Levin wrote:
> > > On Sun, Nov 16, 2025 at 11:42:24AM -0800, Eric Biggers wrote:
> > > > On Sun, Nov 16, 2025 at 12:19:42PM -0500, Sasha Levin wrote:
> > > > > Subject: lib/crypto: arm/curve25519: Disable on CPU_BIG_ENDIAN
> > > > >
> > > > > Thanks!
> > > >
> > > > I assume that you meant to write something meaningful in this message.
> > > 
> > > What else did you expect to see here?
> > 
> > Maybe some actual information that wasn't already in the email that
> > you're replying to?  What are you trying to accomplish?
> 
> Letting you know that your backport was queued up?

Maybe you should have mentioned that then?

- Eric

Re: [PATCH 6.12] lib/crypto: arm/curve25519: Disable on CPU_BIG_ENDIAN

[Sasha Levin]

On Sun, Nov 16, 2025 at 05:50:52PM -0800, Eric Biggers wrote:
>On Sun, Nov 16, 2025 at 08:43:12PM -0500, Sasha Levin wrote:
>> On Sun, Nov 16, 2025 at 05:25:13PM -0800, Eric Biggers wrote:
>> > On Sun, Nov 16, 2025 at 07:42:34PM -0500, Sasha Levin wrote:
>> > > On Sun, Nov 16, 2025 at 11:42:24AM -0800, Eric Biggers wrote:
>> > > > On Sun, Nov 16, 2025 at 12:19:42PM -0500, Sasha Levin wrote:
>> > > > > Subject: lib/crypto: arm/curve25519: Disable on CPU_BIG_ENDIAN
>> > > > >
>> > > > > Thanks!
>> > > >
>> > > > I assume that you meant to write something meaningful in this message.
>> > >
>> > > What else did you expect to see here?
>> >
>> > Maybe some actual information that wasn't already in the email that
>> > you're replying to?  What are you trying to accomplish?
>>
>> Letting you know that your backport was queued up?
>
>Maybe you should have mentioned that then?

Oh!

Apparently if I call git-send-email with --subject, it'll still strip the first
line from the patch file.

The first line was "This patch has been queued up for the ${KERNEL_VERSION}
stable tree." :)

Thanks for pointing it out, I've fixed up the script.

-- 
Thanks,
Sasha