linux-kernel - Re: [PATCH] x86/asm/entry/32, selftests: Add test_syscall

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Message-ID: <CAGXu5jLojq53z82Z0_Wo2qXSxDjZ1ZGmiCKoBO9pmDYG1DyeUQ@mail.gmail.com>
Date:	Wed, 10 Jun 2015 13:20:40 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Denys Vlasenko <dvlasenk@...hat.com>
Cc:	"CC: Ingo Molnar <mingo@...nel.org>, Linus Torvalds
	<torvalds@...ux-foundation.org>, Steven Rostedt <rostedt@...dmis.org>,
	Borislav Petkov <bp@...en8.de>, H. Peter Anvin" 
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/asm/entry/32, selftests: Add test_syscall_vdso test

On Wed, Jun 10, 2015 at 1:15 PM, Denys Vlasenko <dvlasenk@...hat.com> wrote:
> On 06/10/2015 10:00 PM, Kees Cook wrote:
>>> +       printf("[SKIP]\tAT_SYSINFO not supplied, can't test\n");
>>> +       exit(0); /* this is not a test failure */
>>
>> Why is that not a test failure? It would mean it didn't actually test
>> anything, which seems like a failure to me.
>
> Are you objecting to comment wording, or to exiting with 0?
>
> I exit with 0 because no bug was detected.

It seemed like a test failure to me: you're failing open ("couldn't
configure test, I guess everything is okay") instead of failing closed
("couldn't configure test, something is terribly wrong").

If you can't locate how to make a syscall, then the test should fail,
IMO, since it was not possible to perform the test, so you don't know
if flags are being correctly handled across syscalls.

-Kees

-- 
Kees Cook
Chrome OS Security
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