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Date:   Thu, 15 Mar 2018 13:01:17 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc:     Petr Mladek <pmladek@suse.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        "Tobin C . Harding" <me@tobin.cc>, Joe Perches <joe@perches.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Michal Hocko <mhocko@suse.cz>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Subject: Re: [PATCH v3] vsprintf: Prevent crash when dereferencing invalid
 pointers
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On Thu, 15 Mar 2018 17:03:09 +0900
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> wrote:

> On (03/15/18 16:58), Sergey Senozhatsky wrote:
> > On (03/14/18 15:09), Petr Mladek wrote:
> > [..]  
> > > +static const char *check_pointer_access(const void *ptr)
> > > +{
> > > +	unsigned char byte;
> > > +
> > > +	if (!ptr)
> > > +		return "(null)";
> > > +
> > > +	if (probe_kernel_read(&byte, ptr, 1))  
> >                                         ^^^^^
> > Why one byte? 			     sizeof(ptr)?  
> 
> I think there is a shorter version - probe_kernel_address(),
> which, seems, was designed for this particular kind of stuff.
> 
> 	void *p;
> 
> 	if (probe_kernel_address(ptr, p))
> 		....
>

Agreed.

-- Steve