linux-kernel - Re: [PATCH v3] vsprintf: Prevent crash when dereferencing invalid pointers

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Message-ID: <20180329145312.4uqygrjqy3fqyl26@pathway.suse.cz>
Date:   Thu, 29 Mar 2018 16:53:12 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        "Tobin C . Harding" <me@...in.cc>, Joe Perches <joe@...ches.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.cz>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [PATCH v3] vsprintf: Prevent crash when dereferencing invalid
 pointers

On Fri 2018-03-16 20:19:35, Andy Shevchenko wrote:
> On Thu, 2018-03-15 at 16:26 +0100, Petr Mladek wrote:
> > On Thu 2018-03-15 15:09:03, Andy Shevchenko wrote:
> > > On Wed, 2018-03-14 at 15:09 +0100, Petr Mladek wrote:
> > > > We already prevent crash when dereferencing some obviously broken
> > > > pointers. But the handling is not consistent. Sometimes we print
> > > > "(null)"
> > > > only for pure NULL pointer, sometimes for pointers in the first
> > > > page and 
> > > 
> > > 
> > > > sometimes also for pointers in the last page (error codes).
> > > 
> > > I still think that printing a hex value of the error code is much
> > > better
> > > than some odd "(efault)".
> > 
> > Do you mean (err:0e)? Google gives rather confusing answers for this.
> 
> More like "(0xHHHH)" (we have already more than 512 error code numbers.

Hmm, I have never seen the error code in this form. Also google gives
rather confusing results when searching, for example for "(0x000E)".

Best Regards,
Petr