Re: [PATCH] vsprintf: Make "null" pointer dereference more robust

Petr Mladek
2018-03-05T14:53:10Z

On Fri 2018-03-02 16:17:34, Andy Shevchenko wrote:
> On Fri, 2018-03-02 at 13:53 +0100, Petr Mladek wrote:
> > %p has many modifiers where the pointer is dereferenced. An invalid
> > pointer might cause kernel to crash silently.
> >
> > Note that printk() formats the string under logbuf_lock. Any recursive
> > printks are redirected to the printk_safe implementation and the
> > messages
> > are stored into per-CPU buffers. These buffers might be eventually
> > flushed
> > in printk_safe_flush_on_panic() but it is not guaranteed.
> >
> > In general, we should do our best to get useful message from printk().
> > All pointers to the first memory page must be invalid. Let's prevent
> > the dereference and print "(null)" in this case. This is already done
> > in many other situations, including "%s" format handling and many
> > page fault handlers.
> >
>
>
> With such explanation it makes at least clear for the reader why it's
> done.
>
> Thanks!
>
> Would you be okay if I take this one as a first in my series and
> resubmit the series based on it?

Makes sense. Feel free to go on.

Best Regards,
Petr