[PATCH] crypto: x86/curve25519 - fix cpu feature checking logic in mod_exit

[PATCH] crypto: x86/curve25519 - fix cpu feature checking logic in mod_exit

[Hangbin Liu]

In curve25519_mod_init() the curve25519_alg will be registered only when
(X86_FEATURE_BMI2 && X86_FEATURE_ADX). But in curve25519_mod_exit()
it still checks (X86_FEATURE_BMI2 || X86_FEATURE_ADX) when do crypto
unregister. This will trigger a BUG_ON in crypto_unregister_alg() as
alg->cra_refcnt is 0 if the cpu only supports one of X86_FEATURE_BMI2
and X86_FEATURE_ADX.

Fixes: 07b586fe0662 ("crypto: x86/curve25519 - replace with formally verified implementation")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
---
 arch/x86/crypto/curve25519-x86_64.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/crypto/curve25519-x86_64.c b/arch/x86/crypto/curve25519-x86_64.c
index 6706b6cb1d0f..38caf61cd5b7 100644
--- a/arch/x86/crypto/curve25519-x86_64.c
+++ b/arch/x86/crypto/curve25519-x86_64.c
@@ -1500,7 +1500,7 @@ static int __init curve25519_mod_init(void)
 static void __exit curve25519_mod_exit(void)
 {
 	if (IS_REACHABLE(CONFIG_CRYPTO_KPP) &&
-	    (boot_cpu_has(X86_FEATURE_BMI2) || boot_cpu_has(X86_FEATURE_ADX)))
+	    static_branch_likely(&curve25519_use_bmi2_adx))
 		crypto_unregister_kpp(&curve25519_alg);
 }
 
-- 
2.26.3

Re: [PATCH] crypto: x86/curve25519 - fix cpu feature checking logic in mod_exit

[Jason A. Donenfeld]

On Thu, Jun 3, 2021 at 7:53 AM Hangbin Liu <liuhangbin@gmail.com> wrote:
>
> In curve25519_mod_init() the curve25519_alg will be registered only when
> (X86_FEATURE_BMI2 && X86_FEATURE_ADX). But in curve25519_mod_exit()
> it still checks (X86_FEATURE_BMI2 || X86_FEATURE_ADX) when do crypto
> unregister. This will trigger a BUG_ON in crypto_unregister_alg() as
> alg->cra_refcnt is 0 if the cpu only supports one of X86_FEATURE_BMI2
> and X86_FEATURE_ADX.
>
> Fixes: 07b586fe0662 ("crypto: x86/curve25519 - replace with formally verified implementation")
> Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
> ---
>  arch/x86/crypto/curve25519-x86_64.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/crypto/curve25519-x86_64.c b/arch/x86/crypto/curve25519-x86_64.c
> index 6706b6cb1d0f..38caf61cd5b7 100644
> --- a/arch/x86/crypto/curve25519-x86_64.c
> +++ b/arch/x86/crypto/curve25519-x86_64.c
> @@ -1500,7 +1500,7 @@ static int __init curve25519_mod_init(void)
>  static void __exit curve25519_mod_exit(void)
>  {
>         if (IS_REACHABLE(CONFIG_CRYPTO_KPP) &&
> -           (boot_cpu_has(X86_FEATURE_BMI2) || boot_cpu_has(X86_FEATURE_ADX)))
> +           static_branch_likely(&curve25519_use_bmi2_adx))
>                 crypto_unregister_kpp(&curve25519_alg);
>  }

Looks like the error is actually that the `||` should be a `&&`. But
if you'd like to branch on that static key instead, that's fine.

Cc: stable@vger.kernel.org
Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com>

Re: [PATCH] crypto: x86/curve25519 - fix cpu feature checking logic in mod_exit

[Hangbin Liu]

On Thu, Jun 3, 2021 at 6:24 PM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
> >         if (IS_REACHABLE(CONFIG_CRYPTO_KPP) &&
> > -           (boot_cpu_has(X86_FEATURE_BMI2) || boot_cpu_has(X86_FEATURE_ADX)))
> > +           static_branch_likely(&curve25519_use_bmi2_adx))
> >                 crypto_unregister_kpp(&curve25519_alg);
> >  }
>
> Looks like the error is actually that the `||` should be a `&&`. But
> if you'd like to branch on that static key instead, that's fine.

Yes, the code would be shorter by checking the static key :)

Thanks
hangbin

Re: [PATCH] crypto: x86/curve25519 - fix cpu feature checking logic in mod_exit

[Herbert Xu]

On Thu, Jun 03, 2021 at 01:53:40AM -0400, Hangbin Liu wrote:
> In curve25519_mod_init() the curve25519_alg will be registered only when
> (X86_FEATURE_BMI2 && X86_FEATURE_ADX). But in curve25519_mod_exit()
> it still checks (X86_FEATURE_BMI2 || X86_FEATURE_ADX) when do crypto
> unregister. This will trigger a BUG_ON in crypto_unregister_alg() as
> alg->cra_refcnt is 0 if the cpu only supports one of X86_FEATURE_BMI2
> and X86_FEATURE_ADX.
> 
> Fixes: 07b586fe0662 ("crypto: x86/curve25519 - replace with formally verified implementation")
> Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
> ---
>  arch/x86/crypto/curve25519-x86_64.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH] crypto: x86/curve25519 - fix cpu feature checking logic in mod_exit

[Jason A. Donenfeld]

Hi Herbert,

Is there a reason why in
https://git.kernel.org/pub/scm/linux/kernel/git/herbert/cryptodev-2.6.git/patch/?id=1b82435d17774f3eaab35dce239d354548aa9da2
you didn't mark it with the Cc: stable@ line that I included above my
Reviewed-by? Netdev no longer has their own stable process. Do you
have something else in mind for this?

Jason

Re: [PATCH] crypto: x86/curve25519 - fix cpu feature checking logic in mod_exit

[Herbert Xu]

On Fri, Jun 11, 2021 at 12:07:43PM +0200, Jason A. Donenfeld wrote:
> Hi Herbert,
> 
> Is there a reason why in
> https://git.kernel.org/pub/scm/linux/kernel/git/herbert/cryptodev-2.6.git/patch/?id=1b82435d17774f3eaab35dce239d354548aa9da2
> you didn't mark it with the Cc: stable@ line that I included above my
> Reviewed-by? Netdev no longer has their own stable process. Do you
> have something else in mind for this?

Hi Jason:

This patch has a Fixes header set and it'll be automatically pushed
to stable.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt