From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754497AbZKSRc4 (ORCPT ); Thu, 19 Nov 2009 12:32:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754290AbZKSRcy (ORCPT ); Thu, 19 Nov 2009 12:32:54 -0500 Received: from relay3.sgi.com ([192.48.152.1]:43087 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753845AbZKSRcF (ORCPT ); Thu, 19 Nov 2009 12:32:05 -0500 From: Robin Holt Message-Id: <20091119173209.848367000@alcatraz.americas.sgi.com> User-Agent: quilt/0.47-1 Date: Thu, 19 Nov 2009 11:32:03 -0600 To: Ingo Molnar , tglx@linutronix.de Cc: Robin Holt , Jack Steiner , linux-kernel Subject: [patch 6/8] x86: UV - XPC NULL deref when mesq becomes empty. References: <20091119173157.337874000@alcatraz.americas.sgi.com> Content-Disposition: inline; filename=xpc_fix_xpc_get_fifo_entry_uv Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Under heavy load conditions, our set of xpc messages may become exhausted. The code handles this correctly with the exception of the management code which hits a NULL pointer dereference. To: Ingo Molnar To: tglx@linutronix.de Signed-off-by: Robin Holt Cc: Jack Steiner Cc: linux-kernel@vger.kernel.org --- drivers/misc/sgi-xp/xpc_uv.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) Index: linux-x86/drivers/misc/sgi-xp/xpc_uv.c =================================================================== --- linux-x86.orig/drivers/misc/sgi-xp/xpc_uv.c 2009-11-18 21:41:23.000000000 -0600 +++ linux-x86/drivers/misc/sgi-xp/xpc_uv.c 2009-11-18 21:41:26.000000000 -0600 @@ -949,11 +949,13 @@ xpc_get_fifo_entry_uv(struct xpc_fifo_he head->first = first->next; if (head->first == NULL) head->last = NULL; + + head->n_entries--; + BUG_ON(head->n_entries < 0); + + first->next = NULL; } - head->n_entries--; - BUG_ON(head->n_entries < 0); spin_unlock_irqrestore(&head->lock, irq_flags); - first->next = NULL; return first; }