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Date:   Fri, 12 Feb 2021 12:52:01 +0100
From:   Petr Mladek <pmladek@suse.com>
To:     Timur Tabi <timur@kernel.org>
Cc:     Steven Rostedt <rostedt@goodmis.org>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Matthew Wilcox <willy@infradead.org>,
        akpm@linux-foundation.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        roman.fietze@magna.com, Kees Cook <keescook@chromium.org>,
        John Ogness <john.ogness@linutronix.de>,
        akinobu.mita@gmail.com, glider@google.com,
        Andrey Konovalov <andreyknvl@google.com>,
        Marco Elver <elver@google.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Pavel Machek <pavel@ucw.cz>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org
Subject: Re: [PATCH 3/3] lib/vsprintf: make-printk-non-secret printks all
 addresses as unhashed
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References: <20210210051814.845713-1-timur@kernel.org>
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 <YCPily3XZY4Cw6tU@alley>
 <ca1371e2-8df3-3e28-b5d6-b4bc0fbe6b70@kernel.org>
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Hi,

I have realized that I did not comment the two ideas.

On Wed 2021-02-10 11:27:45, Timur Tabi wrote:
> 
> 
> On 2/10/21 7:41 AM, Petr Mladek wrote:
> > 
> > The option causes that vsprintf() will not hash pointers. Yes, it is
> > primary used by printk(). But it is used also in some other
> > interfaces, especially trace_printk(), seq_buf() API. The naked
> > pointers might appear more or less anywhere, including procfs,
> > sysfs, debugfs.
>
> Fair point.  Shouldn't calls to seq_buf_printf() (and any printk usage that
> always exists in the context of a user-space process) use %pK anyway?

seq_buf is a handy API that might be used for different purpose.
For example, it seems to be used ftrace where people might want
to see real pointers when debugging.

> Hmmm.... maybe vsprintf() should automatically replace %p with %pK if it
> detects a user-space context?

I am not sure if there is an easy and reliable way how to detect the
user-space context. On some architectures, it might be possible to
guess it by the address of the buffer. But it will not work when
the message is temporary printed into a local buffer and copied
later.

Let's keep it simple. Heuristics often become very complex over time.

Best Regards,
Petr