From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751261AbaH1Lcn (ORCPT ); Thu, 28 Aug 2014 07:32:43 -0400 Received: from mx1.redhat.com ([209.132.183.28]:31220 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750858AbaH1Lcm (ORCPT ); Thu, 28 Aug 2014 07:32:42 -0400 Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20140826154129.GA4481@ada> References: <20140826154129.GA4481@ada> To: Andreea-Cristina Bernat Cc: dhowells@redhat.com, shemming@brocade.com, linux-kernel@vger.kernel.org, paulmck@linux.vnet.ibm.com Subject: Re: [PATCH RFC] rcu: assoc_array: Add critical section to avoid a bug MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <3613.1409225551.1@warthog.procyon.org.uk> Date: Thu, 28 Aug 2014 12:32:31 +0100 Message-ID: <3614.1409225551@warthog.procyon.org.uk> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andreea-Cristina Bernat wrote: > * The function "assoc_array_gc()" could be preempted between the call to > "assoc_array_apply_edit()" call and the assignment > "edit->array->nr_leaves_on_tree = nr_leaves_on_tree;", so the grace > period could complete. The bug is real, but this patch isn't the right solution. The edit script should be considered inaccessible to a function the moment it calls assoc_array_apply_edit() or assoc_array_cancel_edit(). I think this is a better way. David --- assoc_array.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) commit 10c26fcc224c0515e15272515e7b9006cb08adc8 Author: David Howells Date: Wed Aug 27 18:39:44 2014 +0100 KEYS: Fix use-after-free in assoc_array_gc() An edit script should be considered inaccessible by a function once it has called assoc_array_apply_edit() or assoc_array_cancel_edit(). However, assoc_array_gc() is accessing the edit script just after the gc_complete: label. Reported-by: Andreea-Cristina Bernat Signed-off-by: David Howells diff --git a/lib/assoc_array.c b/lib/assoc_array.c index c0b1007011e1..ae146f0734eb 100644 --- a/lib/assoc_array.c +++ b/lib/assoc_array.c @@ -1735,7 +1735,7 @@ ascend_old_tree: gc_complete: edit->set[0].to = new_root; assoc_array_apply_edit(edit); - edit->array->nr_leaves_on_tree = nr_leaves_on_tree; + array->nr_leaves_on_tree = nr_leaves_on_tree; return 0; enomem: