linux-kernel - Re: [PATCH v2] KEYS: trusted: Remove redundant static calls usage

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Message-ID: <CAB=+i9RGN0+S1siV7qjiZLSpfVMzsSu-8bTQ2yRi_zkRTiRbXQ@mail.gmail.com>
Date:   Fri, 6 Oct 2023 14:56:26 +0900
From:   Hyeonggon Yoo <42.hyeyoo@...il.com>
To:     Sumit Garg <sumit.garg@...aro.org>
Cc:     torvalds@...ux-foundation.org, jarkko@...nel.org,
        peterz@...radead.org, zohar@...ux.ibm.com,
        linux-kernel@...r.kernel.org, linux-integrity@...r.kernel.org,
        jejb@...ux.ibm.com, David.Kaplan@....com, bp@...en8.de,
        mingo@...nel.org, x86@...nel.org, regressions@...mhuis.info
Subject: Re: [PATCH v2] KEYS: trusted: Remove redundant static calls usage

On Fri, Oct 6, 2023 at 2:18 PM Sumit Garg <sumit.garg@...aro.org> wrote:
>
> Static calls invocations aren't well supported from module __init and
> __exit functions. Especially the static call from cleanup_trusted() led
> to a crash on x86 kernel with CONFIG_DEBUG_VIRTUAL=y.
>
> However, the usage of static call invocations for trusted_key_init()
> and trusted_key_exit() don't add any value from either a performance or
> security perspective. Hence switch to use indirect function calls instead.
>
> Note here that although it will fix the current crash report, ultimately
> the static call infrastructure should be fixed to either support its
> future usage from module __init and __exit functions or not.
>
> Reported-by: Hyeonggon Yoo <42.hyeyoo@...il.com>
> Link: https://lore.kernel.org/lkml/ZRhKq6e5nF%2F4ZIV1@fedora/#t
> Fixes: 5d0682be3189 ("KEYS: trusted: Add generic trusted keys framework")
> Signed-off-by: Sumit Garg <sumit.garg@...aro.org>

I verified that this patch fixes the original problem.
Thanks!

Feel free to add:
Tested-By: Hyeonggon Yoo <42.hyeyoo@...il.com>


Hyeonggon

> ---
>
> Changes in v2:
> - Polish commit message as per comments from Mimi
>
>  security/keys/trusted-keys/trusted_core.c | 13 +++++--------
>  1 file changed, 5 insertions(+), 8 deletions(-)
>
> diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c
> index c6fc50d67214..85fb5c22529a 100644
> --- a/security/keys/trusted-keys/trusted_core.c
> +++ b/security/keys/trusted-keys/trusted_core.c
> @@ -44,13 +44,12 @@ static const struct trusted_key_source trusted_key_sources[] = {
>  #endif
>  };
>
> -DEFINE_STATIC_CALL_NULL(trusted_key_init, *trusted_key_sources[0].ops->init);
>  DEFINE_STATIC_CALL_NULL(trusted_key_seal, *trusted_key_sources[0].ops->seal);
>  DEFINE_STATIC_CALL_NULL(trusted_key_unseal,
>                         *trusted_key_sources[0].ops->unseal);
>  DEFINE_STATIC_CALL_NULL(trusted_key_get_random,
>                         *trusted_key_sources[0].ops->get_random);
> -DEFINE_STATIC_CALL_NULL(trusted_key_exit, *trusted_key_sources[0].ops->exit);
> +static void (*trusted_key_exit)(void);
>  static unsigned char migratable;
>
>  enum {
> @@ -359,19 +358,16 @@ static int __init init_trusted(void)
>                 if (!get_random)
>                         get_random = kernel_get_random;
>
> -               static_call_update(trusted_key_init,
> -                                  trusted_key_sources[i].ops->init);
>                 static_call_update(trusted_key_seal,
>                                    trusted_key_sources[i].ops->seal);
>                 static_call_update(trusted_key_unseal,
>                                    trusted_key_sources[i].ops->unseal);
>                 static_call_update(trusted_key_get_random,
>                                    get_random);
> -               static_call_update(trusted_key_exit,
> -                                  trusted_key_sources[i].ops->exit);
> +               trusted_key_exit = trusted_key_sources[i].ops->exit;
>                 migratable = trusted_key_sources[i].ops->migratable;
>
> -               ret = static_call(trusted_key_init)();
> +               ret = trusted_key_sources[i].ops->init();
>                 if (!ret)
>                         break;
>         }
> @@ -388,7 +384,8 @@ static int __init init_trusted(void)
>
>  static void __exit cleanup_trusted(void)
>  {
> -       static_call_cond(trusted_key_exit)();
> +       if (trusted_key_exit)
> +               (*trusted_key_exit)();
>  }
>
>  late_initcall(init_trusted);
> --
> 2.34.1
>