linux-kernel - Re: [PATCH v2 1/4] kselftests/arm64: add a basic Pointer Authentication test

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Message-ID: <fa24987e-c8e9-0130-d2bc-ec114a729491@gmail.com>
Date:   Thu, 17 Sep 2020 14:38:01 +0100
From:   Boyan Karatotev <boian4o1@...il.com>
To:     Amit Kachhap <amit.kachhap@....com>,
        Boyan Karatotev <boyan.karatotev@....com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     vincenzo.frascino@....com, Shuah Khan <shuah@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
Subject: Re: [PATCH v2 1/4] kselftests/arm64: add a basic Pointer
 Authentication test

On 16/09/2020 1:11 pm, Amit Kachhap wrote:
> On 8/31/20 4:34 PM, Boyan Karatotev wrote:
>> PAuth signs and verifies return addresses on the stack. It does so by
>> +
>> +/* check that a corrupted PAC results in SIGSEGV */
>> +TEST_SIGNAL(corrupt_pac, SIGSEGV)
>> +{
>> +    ASSERT_PAUTH_ENABLED();
>> +
>> +    pac_corruptor();
>
> With 8.6-Pauth extension merged in arm tree [1]. It makes sense to
> verify PAC corruption for both SIGSEGV and SIGILL signals.
>
> Code something like below handles both the cases.
>
>
-----------------------------------------------------------------------------------
>
>  int exec_sign_all(struct signatures *signed_vals, size_t val)
> @@ -187,12 +188,29 @@ int exec_sign_all(struct signatures *signed_vals,
> size_t val)
>         return 0;
>  }
>
> -/* check that a corrupted PAC results in SIGSEGV */
> -TEST_SIGNAL(corrupt_pac, SIGSEGV)
> +sigjmp_buf jmpbuf;
> +void pac_signal_handler(int signum, siginfo_t *si, void *uc)
>  {
> -       ASSERT_PAUTH_ENABLED();
> +       if (signum == SIGSEGV || signum == SIGILL) {
> +               siglongjmp(jmpbuf, 1);
> +       }
> +}
> +
> +/* check that a corrupted PAC results in SIGSEGV or SIGILL */
> +TEST(corrupt_pac)
> +{
> +       struct sigaction sa;
>
> -       pac_corruptor();
> +       ASSERT_PAUTH_ENABLED();
> +       if (sigsetjmp(jmpbuf, 1) == 0) {
> +               sa.sa_sigaction = pac_signal_handler;
> +               sa.sa_flags = SA_SIGINFO;
> +               sigemptyset(&sa.sa_mask);
> +               sigaction(SIGSEGV, &sa, NULL);
> +               sigaction(SIGILL, &sa, NULL);
> +               pac_corruptor();
> +               ASSERT_TRUE(0) TH_LOG("SIGSEGV/SIGILL signal did not
> occur");
> +       }
>  }
>
>  /*
> @@ -265,7 +283,7 @@ TEST(single_thread_different_keys)
>
>                 tmp = n_same_single_set(&signed_vals, nkeys);
>
---------------------------------------------------------------------------------------
>
>
>
> Thanks,
> Amit Daniel
>
> [1]:
>
https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/log/?h=for-next/ptrauth

Okay, I will add this and post it with the next version.

Regards,
Boyan