From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752112AbeESA2T (ORCPT ); Fri, 18 May 2018 20:28:19 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:41420 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750957AbeESA2R (ORCPT ); Fri, 18 May 2018 20:28:17 -0400 Date: Fri, 18 May 2018 17:28:15 -0700 From: Matthew Wilcox To: Andrew Morton Cc: Roman Kagan , linux-kernel@vger.kernel.org Subject: Re: [PATCH] idr: fix invalid ptr dereference on item delete Message-ID: <20180519002815.GA21615@bombadil.infradead.org> References: <20180518175025.GD6361@bombadil.infradead.org> <20180518153138.459c78a83c6bada41b4b187d@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180518153138.459c78a83c6bada41b4b187d@linux-foundation.org> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 18, 2018 at 03:31:38PM -0700, Andrew Morton wrote: > On Fri, 18 May 2018 10:50:25 -0700 Matthew Wilcox wrote: > > If the radix tree underlying the IDR happens to be full and we attempt > > to remove an id which is larger than any id in the IDR, we will call > > __radix_tree_delete() with an uninitialised 'slot' pointer, at which > > point anything could happen. This was easiest to hit with a single entry > > at id 0 and attempting to remove a non-0 id, but it could have happened > > with 64 entries and attempting to remove an id >= 64. > > > > Fixes: 0a835c4f090a ("Reimplement IDR and IDA using the radix tree") > > Reported-by: syzbot+35666cba7f0a337e2e79@syzkaller.appspotmail.com > > Debugged-by: Roman Kagan > > Signed-off-by: Matthew Wilcox > > Neither of the changelogs I'm seeing attempt to describe the end-user > impact of the bug. People like to know that so they can decide which > kernel version(s) need patching, so please always remember it. The problem is that it could be user-triggerable a dozen different ways. > Looknig at the sysbot report, the impact is at least "privileged user > can trigger a WARN", but I assume there could be worse, > as-yet-undiscovered impacts. So I'm thinking a cc:stable is needed, > yes? I thought if I used the Fixes: tag it would automatically get picked up. Did I misunderstand? I can imagine many different parts of the kernel that use the IDR could trigger such a warning (although syzbot should probably have tripped over them before now) so I wouldn't downplay it to "only privileged users".