From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754428AbaDRRJn (ORCPT ); Fri, 18 Apr 2014 13:09:43 -0400 Received: from mail-qa0-f48.google.com ([209.85.216.48]:42143 "EHLO mail-qa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752335AbaDRRJj (ORCPT ); Fri, 18 Apr 2014 13:09:39 -0400 Date: Fri, 18 Apr 2014 13:09:35 -0400 From: Tejun Heo To: Lai Jiangshan Cc: linux-kernel@vger.kernel.org, Andrew Morton , Jean Delvare , Monam Agarwal , Jeff Layton , Andreas Gruenbacher , Stephen Hemminger Subject: Re: [PATCH 3/8] idr: fix NULL pointer dereference when ida_remove(unallocated_id) Message-ID: <20140418170935.GA23576@htj.dyndns.org> References: <1397825404-12039-1-git-send-email-laijs@cn.fujitsu.com> <1397825404-12039-4-git-send-email-laijs@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1397825404-12039-4-git-send-email-laijs@cn.fujitsu.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 18, 2014 at 08:49:50PM +0800, Lai Jiangshan wrote: > If the ida has at least one existed_id, and when an special unallocated_id existing id or allocated id when an unallocated id which meets a certain condition is passed to... > is passed to the ida_remove(), the system will crash because it hits NULL > pointer dereference. > > This special unallocated_id is that it shares the same lowest idr layer with The condition is that the ID shares the... > an exsited_id, but the idr slot is different(if the unallocated_id is allocated). the existing ID, would be different if the unallocated ID were to be allocated. > In this case the supposed idr slot of the unallocated_id is NULL, matching for > It means @bitmap == NULL, and when the code dereference it, it crash the kernel. causing @bitmap to be NULL which the function dereferences without checking crashing the kernel. > > See the test code: > > static void test3(void) > { > int id; > DEFINE_IDA(test_ida); > > printk(KERN_INFO "Start test3\n"); > if (ida_pre_get(&test_ida, GFP_KERNEL) < 0) return; > if (ida_get_new(&test_ida, &id) < 0) return; > ida_remove(&test_ida, 4000); /* bug: null deference here */ > printk(KERN_INFO "End of test3\n"); > } > > It only happens when unallocated_id, it is caller's fault. It is not It happens only when the caller tries to free an unallocated ID which is the caller's fault. > a bug. But it is better to add the proper check and complains instead and complain rather than crashing the kernel > of crashing the kernel. > > Signed-off-by: Lai Jiangshan Acked-by: Tejun Heo Thanks. -- tejun