From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Shevchenko Subject: Re: [PATCH] vsprintf: Do not break early boot with probing addresses Date: Mon, 13 May 2019 12:13:20 +0300 Message-ID: <20190513091320.GK9224@smile.fi.intel.com> References: <20190510081635.GA4533@jagdpanzerIV> <20190510084213.22149-1-pmladek@suse.com> <20190510122401.21a598f6@gandalf.local.home> <096d6c9c17b3484484d9d9d3f3aa3a7c@AcuMS.aculab.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <096d6c9c17b3484484d9d9d3f3aa3a7c@AcuMS.aculab.com> Sender: linux-kernel-owner@vger.kernel.org To: David Laight Cc: 'christophe leroy' , Steven Rostedt , Petr Mladek , Linus Torvalds , Rasmus Villemoes , "Tobin C . Harding" , Michal Hocko , Sergey Senozhatsky , Sergey Senozhatsky , "linux-kernel@vger.kernel.org" , Michael Ellerman , "linuxppc-dev@lists.ozlabs.org" , Russell Currey , Stephen Rothwell , Heiko Carstens , "linux-arch@vger.kernel.org" , "linux-s390@vger.kernel.org" List-Id: linux-arch.vger.kernel.org On Mon, May 13, 2019 at 08:52:41AM +0000, David Laight wrote: > 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 wrote: > > >> - 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". It's a special, thus it's in parenthesis, though somebody can be misguided. > > 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)" ? In both cases it should be limited to the size of pointer (8 or 16 characters). Something like "(e:%4d)" would work for error codes. The "(null)" is good enough by itself and already an established practice.. -- With Best Regards, Andy Shevchenko From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga07.intel.com ([134.134.136.100]:34770 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728616AbfEMJN1 (ORCPT ); Mon, 13 May 2019 05:13:27 -0400 Date: Mon, 13 May 2019 12:13:20 +0300 From: Andy Shevchenko Subject: Re: [PATCH] vsprintf: Do not break early boot with probing addresses Message-ID: <20190513091320.GK9224@smile.fi.intel.com> References: <20190510081635.GA4533@jagdpanzerIV> <20190510084213.22149-1-pmladek@suse.com> <20190510122401.21a598f6@gandalf.local.home> <096d6c9c17b3484484d9d9d3f3aa3a7c@AcuMS.aculab.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <096d6c9c17b3484484d9d9d3f3aa3a7c@AcuMS.aculab.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: David Laight Cc: 'christophe leroy' , Steven Rostedt , Petr Mladek , Linus Torvalds , Rasmus Villemoes , "Tobin C . Harding" , Michal Hocko , Sergey Senozhatsky , Sergey Senozhatsky , "linux-kernel@vger.kernel.org" , Michael Ellerman , "linuxppc-dev@lists.ozlabs.org" , Russell Currey , Stephen Rothwell , Heiko Carstens , "linux-arch@vger.kernel.org" , "linux-s390@vger.kernel.org" , Martin Schwidefsky Message-ID: <20190513091320.1ZqC-JL0QLpgZiAEDAqK_gfjSO6wDFbjpn4v4t2QXOE@z> On Mon, May 13, 2019 at 08:52:41AM +0000, David Laight wrote: > 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 wrote: > > >> - 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". It's a special, thus it's in parenthesis, though somebody can be misguided. > > 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)" ? In both cases it should be limited to the size of pointer (8 or 16 characters). Something like "(e:%4d)" would work for error codes. The "(null)" is good enough by itself and already an established practice.. -- With Best Regards, Andy Shevchenko