linux-kernel - RE: [PATCH] vsprintf: Do not break early boot with probing addresses

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Message-ID: <096d6c9c17b3484484d9d9d3f3aa3a7c@AcuMS.aculab.com>
Date:   Mon, 13 May 2019 08:52:41 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'christophe leroy' <christophe.leroy@....fr>,
        Steven Rostedt <rostedt@...dmis.org>,
        Petr Mladek <pmladek@...e.com>
CC:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        "Tobin C . Harding" <me@...in.cc>, Michal Hocko <mhocko@...e.cz>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        "Sergey Senozhatsky" <sergey.senozhatsky.work@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Michael Ellerman" <mpe@...erman.id.au>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        Russell Currey <ruscur@...sell.cc>,
        "Stephen Rothwell" <sfr@...abs.org>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: RE: [PATCH] vsprintf: Do not break early boot with probing addresses

From: christophe leroy
> Sent: 10 May 2019 18:35
> Le 10/05/2019 à 18:24, Steven Rostedt a écrit :
> > On Fri, 10 May 2019 10:42:13 +0200
> > Petr Mladek <pmladek@...e.com> wrote:
> >
> >>   static const char *check_pointer_msg(const void *ptr)
> >>   {
> >> -	char byte;
> >> -
> >>   	if (!ptr)
> >>   		return "(null)";
> >>
> >> -	if (probe_kernel_address(ptr, byte))
> >> +	if ((unsigned long)ptr < PAGE_SIZE || IS_ERR_VALUE(ptr))
> >>   		return "(efault)";

"efault" looks a bit like a spellling mistake for "default".

> > 	< PAGE_SIZE ?
> >
> > do you mean: < TASK_SIZE ?
> 
> I guess not.
> 
> Usually, < PAGE_SIZE means NULL pointer dereference (via the member of a
> struct)

Maybe the caller should pass in a short buffer so that you can return
"(err-%d)" or "(null+%#x)" ?

	David

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