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Date: Wed, 6 Dec 2017 12:40:42 -0800
From: Kees Cook <keescook@...omium.org>
To: Laura Abbott <labbott@...hat.com>
Cc: Alexander Popov <alex.popov@...ux.com>, kernel-hardening@...ts.openwall.com, 
	PaX Team <pageexec@...email.hu>, Brad Spengler <spender@...ecurity.net>, 
	Ingo Molnar <mingo@...nel.org>, Andy Lutomirski <luto@...nel.org>, Tycho Andersen <tycho@...ho.ws>, 
	Mark Rutland <mark.rutland@....com>, Ard Biesheuvel <ard.biesheuvel@...aro.org>, 
	Borislav Petkov <bp@...en8.de>, Thomas Gleixner <tglx@...utronix.de>, "H . Peter Anvin" <hpa@...or.com>, 
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, X86 ML <x86@...nel.org>
Subject: Re: [PATCH RFC v6 5/6] fs/proc: Show STACKLEAK metrics in the /proc
 file system

On Wed, Dec 6, 2017 at 11:22 AM, Laura Abbott <labbott@...hat.com> wrote:
> On 12/05/2017 03:33 PM, Alexander Popov wrote:
>> diff --git a/fs/proc/base.c b/fs/proc/base.c
>> index 28fa852..3569446 100644
>> --- a/fs/proc/base.c
>> +++ b/fs/proc/base.c
>> @@ -2884,6 +2884,17 @@ static int proc_pid_patch_state(struct seq_file *m,
>> struct pid_namespace *ns,
>>   }
>>   #endif /* CONFIG_LIVEPATCH */
>>   +#ifdef CONFIG_STACKLEAK_METRICS
>> +static int proc_lowest_stack(struct seq_file *m, struct pid_namespace
>> *ns,
>> +                               struct pid *pid, struct task_struct *task)
>> +{
>> +       seq_printf(m, "prev_lowest_stack: %pK\nlowest_stack: %pK\n",
>> +                  (void *)task->thread.prev_lowest_stack,
>> +                  (void *)task->thread.lowest_stack);
>> +       return 0;
>> +}
>> +#endif /* CONFIG_STACKLEAK_METRICS */
>> +
>
>
> This just prints the hashed value with the new pointer leak work.
> I don't think we want to print the fully exposed value via %px so
> it's not clear how valuable this proc file is now.

Maybe print the size, not the location?

-Kees

-- 
Kees Cook
Pixel Security

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