From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_2 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 09687C3A589 for ; Tue, 20 Aug 2019 14:38:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DA47022CF7 for ; Tue, 20 Aug 2019 14:38:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729842AbfHTOii (ORCPT ); Tue, 20 Aug 2019 10:38:38 -0400 Received: from mx2.suse.de ([195.135.220.15]:53000 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728248AbfHTOii (ORCPT ); Tue, 20 Aug 2019 10:38:38 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 4B72DAE87; Tue, 20 Aug 2019 14:38:37 +0000 (UTC) Message-ID: <1566311916.11678.26.camel@suse.com> Subject: Re: KASAN: use-after-free Read in iowarrior_disconnect From: Oliver Neukum To: Alan Stern Cc: keescook@chromium.org, gustavo@embeddedor.com, andreyknvl@google.com, syzkaller-bugs@googlegroups.com, gregkh@linuxfoundation.org, syzbot , linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org Date: Tue, 20 Aug 2019 16:38:36 +0200 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.6 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Am Dienstag, den 20.08.2019, 10:18 -0400 schrieb Alan Stern: > On Mon, 19 Aug 2019, Oliver Neukum wrote: > > > Am Montag, den 19.08.2019, 07:48 -0700 schrieb syzbot: > > > Hello, > > > > > > syzbot found the following crash on: > > > > > > HEAD commit: d0847550 usb-fuzzer: main usb gadget fuzzer driver > > > git tree: https://github.com/google/kasan.git usb-fuzzer > > > console output: https://syzkaller.appspot.com/x/log.txt?x=139be302600000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=dbc9c80cc095da19 > > > dashboard link: https://syzkaller.appspot.com/bug?extid=cfe6d93e0abab9a0de05 > > > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12fe6b02600000 > > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1548189c600000 > > > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > > Reported-by: syzbot+cfe6d93e0abab9a0de05@syzkaller.appspotmail.com > > > > > > > #syz test: https://github.com/google/kasan.git d0847550 > > There's no need for us to work at cross purposes on this. We can go > with your approach. > > However, the code is more complicated than your patch accounts for. > The wait can finish in several different ways: > > (1) The control URB succeeds and the interrupt URB gets an > acknowledgment. > > (2) The control URB completes with an error. > > (3) The wait times out. > > (4) A disconnect occurs. I absolutely agree. There is something quite wrong in this driver. Unfortunately this is likely exploitable by a malicious gadget, so just ignoring this is a bad option. I will need to go through the logic. Or do you want to have a shot at it? The patch was really only for testing. I wanted to know whether I was hitting this very issue. This driver will need more surgery. Regards Oliver