linux-kernel - Re: [PATCH][RESEND] lib/vsprintf: make-printk-non-secret printks all addresses as unhashed

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Message-ID: <202102031234.9BF349F@keescook>
Date:   Wed, 3 Feb 2021 12:35:07 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Timur Tabi <timur@...nel.org>, Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        linux-kernel@...r.kernel.org, vbabka@...e.cz, linux-mm@...ck.org,
        willy@...radead.org, akpm@...ux-foundation.org,
        torvalds@...ux-foundation.org, roman.fietze@...na.com,
        john.ogness@...utronix.de,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        akinobu.mita@...il.com
Subject: Re: [PATCH][RESEND] lib/vsprintf: make-printk-non-secret printks all
 addresses as unhashed

On Wed, Feb 03, 2021 at 03:25:13PM -0500, Steven Rostedt wrote:
> On Wed, 3 Feb 2021 12:02:05 -0800
> Kees Cook <keescook@...omium.org> wrote:
> 
> > On Wed, Feb 03, 2021 at 12:58:41PM -0600, Timur Tabi wrote:
> > > On 2/3/21 7:31 AM, Petr Mladek wrote:  
> > > > Also please make sure that lib/test_printf.c will work with
> > > > the new option.  
> > > 
> > > As you suspected, it doesn't work:
> > > 
> > > [  206.966478] test_printf: loaded.
> > > [  206.966528] test_printf: plain 'p' does not appear to be hashed
> > > [  206.966740] test_printf: failed 1 out of 388 tests
> > > 
> > > What should I do about this?
> > > 
> > > On one hand, it is working as expected: %p is not hashed, and that should be
> > > a warning.
> > > 
> > > On the other hand, maybe test_printf should be aware of the command line
> > > parameter and test to make sure that %p is NOT hashed?  
> > 
> > It seems like it'd be best for the test to fail, yes? It _is_ a problem
> > that %p is unhashed; it's just that the failure was intended.
> > 
> 
> I disagree.
> 
> With a big notice that all pointers of unhashed, I don't think we need to
> print it failed when we expect it to fail.
> 
> If anything, skip the test and state:
> 
>   test_printf: hash test skipped because "make-printk-non-secret" is on the
>   command line.

Yeah, I'm fine with "fail" or "skip". "pass" is mainly what I don't
like. :)

-- 
Kees Cook