From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 20 Apr 2011 22:34:54 -0400 (EDT) From: Stephen Powell Message-ID: <248142179.74791.1303353294865.JavaMail.root@md01.wow.synacor.com> In-Reply-To: <20110418115141.GA3157@osiris.boeblingen.de.ibm.com> Subject: Re: [OOPS s390] Unable to handle kernel pointer dereference at virtual kernel address (null) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-Archive: List-Post: To: Heiko Carstens Cc: Jan Glauber , Jonathan Nieder , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, 622570@bugs.debian.org List-ID: On Mon, 18 Apr 2011 07:51:41 -0400 (EDT), Heiko Carstens wrote: > > That's a bug in the pfault interrupt code. After a cleanup patch which > simplified lowcore accesses we are left with a dereference which shouldn't > be there. The patch below should fix it. > The bug was introduced with 2.6.37-rc1. > > diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c > index 9217e33..4cf85fe 100644 > --- a/arch/s390/mm/fault.c > +++ b/arch/s390/mm/fault.c > @@ -558,9 +558,9 @@ static void pfault_interrupt(unsigned int ext_int_code, > * Get the token (= address of the task structure of the affected task). > */ > #ifdef CONFIG_64BIT > - tsk = *(struct task_struct **) param64; > + tsk = (struct task_struct *) param64; > #else > - tsk = *(struct task_struct **) param32; > + tsk = (struct task_struct *) param32; > #endif > > if (subcode & 0x0080) { I applied the above patch and re-built the kernel. I did not apply Jan Glauber's suggested patch, since Heiko's suggested patch seemed to be a "direct hit". I have had the server up for more than 24 hours now, which is definitely a good sign. Without this patch, I've not been able to keep a 2.6.38 s390x kernel up for more than a few hours. Unfortunately, since I can't reproduce the problem on demand, I cannot say with 100% certainty that the problem is fixed, but it looks good and makes sense. -- .''`. Stephen Powell : :' : `. `'` `-