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=-7.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham 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 D187DC47404 for ; Fri, 11 Oct 2019 12:45:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B5BCC21D80 for ; Fri, 11 Oct 2019 12:45:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728184AbfJKMpp (ORCPT ); Fri, 11 Oct 2019 08:45:45 -0400 Received: from mga06.intel.com ([134.134.136.31]:62385 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728147AbfJKMpp (ORCPT ); Fri, 11 Oct 2019 08:45:45 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 11 Oct 2019 05:45:44 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.67,284,1566889200"; d="scan'208";a="219380772" Received: from mattu-haswell.fi.intel.com (HELO [10.237.72.170]) ([10.237.72.170]) by fmsmga004.fm.intel.com with ESMTP; 11 Oct 2019 05:45:43 -0700 Subject: Re: [PATCH 8/8] xhci: Fix NULL pointer dereference in xhci_clear_tt_buffer_complete() From: Mathias Nyman To: Johan Hovold Cc: gregkh@linuxfoundation.org, USB , Alan Stern References: <1570190373-30684-1-git-send-email-mathias.nyman@linux.intel.com> <1570190373-30684-9-git-send-email-mathias.nyman@linux.intel.com> <20191007140245.GD13531@localhost> Message-ID: <1c4b7107-f5e1-4a69-2a73-0e339c7e1072@linux.intel.com> Date: Fri, 11 Oct 2019 15:47:46 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On 8.10.2019 11.15, Mathias Nyman wrote: > On 7.10.2019 17.02, Johan Hovold wrote: >> >> I didn't have time to look into this myself last week, or comment on the >> patch before Greg picked it up, but this clearly isn't the right fix. >> >> As your comment suggests, ep->hcpriv may indeed be NULL here if USB core >> have allocated a new udev. But this only happens after USB has freed the >> old usb_device and the new one happens to get the same address. >> > > You're right, that fix doesn't solve the actual issue, it avoids a few specific > null pointer dereference cases, but leaves both root cause and several other > use-after-free cases open. > >> Note that even the usb_host_endpoint itself (ep) has then been freed and >> reallocated since it is member of struct usb_device, and it is the >> use-after-free that needs fixing. >> >> I've even been able to trigger another NULL-deref in this function >> before a new udev has been allocated, due to the virt dev having been >> freed by xhci_free_dev as part of usb_release_dev: >> >> It seems the xhci clear-tt implementation was incomplete since it did >> not take care to wait for any ongoing work before disabling the >> endpoint. EHCI does this in ehci_endpoint_disable(), but xhci doesn't >> even implement that callback. >> > > So it seems, it might be possible to remove pending clear_tt work for > most endpoints in the .drop_endpoint callbacks, but ep0 is different, > it isn't dropped, we might need to implement the endpoint_disable() > callback for this. > I was able to reproduce the use-after-free issue by faking a endpoint halt, and resetting the endpoint early in enumeration at Get device descriptor request. To fix this I added the endpoint_disable() callback that will wait for clear_tt_work to finish before returning, similar to the ehci solution. It works in my case. the endpoint_disable() callback is called by usb core both before dropping xhci endpoints belonging to a interface, and separately for ep0 before udev is freed during enumeration retry. Both the hack that triggers the issue (LS/FS behind HS bug won't ever enumerate with this) and the fix to prevent use after free can be found in clear_tt_fix branch: git://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git clear_tt_fix I'll send the fix out to the list as well, any chance you could try that out? -Mathias