Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760732Ab2EWSQj (ORCPT ); Wed, 23 May 2012 14:16:39 -0400 Received: from relay1.sgi.com ([192.48.179.29]:48826 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756860Ab2EWSQi (ORCPT ); Wed, 23 May 2012 14:16:38 -0400 Date: Wed, 23 May 2012 13:16:36 -0500 From: Dimitri Sivanich To: Thomas Gleixner Cc: Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Suresh Siddha , Yinghai Lu , Naga Chumbalkar , Jacob Pan , linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86: check for valid irq_cfg pointer in smp_irq_move_cleanup_interrupt Message-ID: <20120523181636.GA2032@sgi.com> References: <20120521164959.GE16454@sgi.com> <20120521211917.GA25567@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1687 Lines: 49 On Mon, May 21, 2012 at 11:34:32PM +0200, Thomas Gleixner wrote: > Don't misunderstand me. The patch is correct, just the explanation > sucks. > Hopefully this explanation is descriptive enough. A NULL pointer dereference can occur in smp_irq_move_cleanup_interrupt() if we haven't yet setup the irq_cfg pointer in the irq_desc.irq_data.chip_data. In create_irq_nr() there is a window where we have set vector_irq in __assign_irq_vector(), but not yet called irq_set_chip_data() to set the irq_cfg pointer. Should an IRQ_MOVE_CLEANUP_VECTOR hit the cpu in question during this time, smp_irq_move_cleanup_interrupt() will attempt to process the aforementioned irq, but panic when accessing irq_cfg. Only continue processing the irq if irq_cfg is non-NULL. Signed-off-by: Dimitri Sivanich --- arch/x86/kernel/apic/io_apic.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) Index: linux/arch/x86/kernel/apic/io_apic.c =================================================================== --- linux.orig/arch/x86/kernel/apic/io_apic.c +++ linux/arch/x86/kernel/apic/io_apic.c @@ -2478,9 +2478,12 @@ asmlinkage void smp_irq_move_cleanup_int if (!desc) continue; - cfg = irq_cfg(irq); raw_spin_lock(&desc->lock); + cfg = irq_cfg(irq); + if (!cfg) + goto unlock; + /* * Check if the irq migration is in progress. If so, we * haven't received the cleanup request yet for this irq. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/