Re: [PATCH 3/3] lib/vsprintf: make-printk-non-secret printks all addresses as unhashed

Petr Mladek
2021-02-12T11:54:34Z

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