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=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 2747FC433B4 for ; Thu, 20 May 2021 09:47:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0C336619BE for ; Thu, 20 May 2021 09:47:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233546AbhETJs3 (ORCPT ); Thu, 20 May 2021 05:48:29 -0400 Received: from mail.kernel.org ([198.145.29.99]:47338 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233685AbhETJp5 (ORCPT ); Thu, 20 May 2021 05:45:57 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 36DF4613F3; Thu, 20 May 2021 09:33:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1621503223; bh=KRE7qo20NlnPA64qN5TVxj7c29c/IWFnQZhyhpJmiZg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qZImb1lEW74v+ezkWCNoFl0zqKbBTLIbWJcAXX1/bx0gzTM/2yiaWoyNFfnnRESgl JsjMGIPfU0KHnOZfC5sySY2Y8tvKEnVbcpiqETviOYtof2bCWVNGYFr8zcVpNlH9GJ op7ue1R0gqHYav5rsjYEIC8JfV3dr47ciQyVoKXg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+eb4674092e6cc8d9e0bd@syzkaller.appspotmail.com, Alan Stern , Anirudh Rayabharam Subject: [PATCH 4.19 107/425] usb: gadget: dummy_hcd: fix gpf in gadget_setup Date: Thu, 20 May 2021 11:17:56 +0200 Message-Id: <20210520092134.970828005@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210520092131.308959589@linuxfoundation.org> References: <20210520092131.308959589@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Anirudh Rayabharam commit 4a5d797a9f9c4f18585544237216d7812686a71f upstream. Fix a general protection fault reported by syzbot due to a race between gadget_setup() and gadget_unbind() in raw_gadget. The gadget core is supposed to guarantee that there won't be any more callbacks to the gadget driver once the driver's unbind routine is called. That guarantee is enforced in usb_gadget_remove_driver as follows: usb_gadget_disconnect(udc->gadget); if (udc->gadget->irq) synchronize_irq(udc->gadget->irq); udc->driver->unbind(udc->gadget); usb_gadget_udc_stop(udc); usb_gadget_disconnect turns off the pullup resistor, telling the host that the gadget is no longer connected and preventing the transmission of any more USB packets. Any packets that have already been received are sure to processed by the UDC driver's interrupt handler by the time synchronize_irq returns. But this doesn't work with dummy_hcd, because dummy_hcd doesn't use interrupts; it uses a timer instead. It does have code to emulate the effect of synchronize_irq, but that code doesn't get invoked at the right time -- it currently runs in usb_gadget_udc_stop, after the unbind callback instead of before. Indeed, there's no way for usb_gadget_remove_driver to invoke this code before the unbind callback. To fix this, move the synchronize_irq() emulation code to dummy_pullup so that it runs before unbind. Also, add a comment explaining why it is necessary to have it there. Reported-by: syzbot+eb4674092e6cc8d9e0bd@syzkaller.appspotmail.com Suggested-by: Alan Stern Acked-by: Alan Stern Signed-off-by: Anirudh Rayabharam Link: https://lore.kernel.org/r/20210419033713.3021-1-mail@anirudhrb.com Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/usb/gadget/udc/dummy_hcd.c | 23 +++++++++++++++-------- 1 file changed, 15 insertions(+), 8 deletions(-) --- a/drivers/usb/gadget/udc/dummy_hcd.c +++ b/drivers/usb/gadget/udc/dummy_hcd.c @@ -914,6 +914,21 @@ static int dummy_pullup(struct usb_gadge spin_lock_irqsave(&dum->lock, flags); dum->pullup = (value != 0); set_link_state(dum_hcd); + if (value == 0) { + /* + * Emulate synchronize_irq(): wait for callbacks to finish. + * This seems to be the best place to emulate the call to + * synchronize_irq() that's in usb_gadget_remove_driver(). + * Doing it in dummy_udc_stop() would be too late since it + * is called after the unbind callback and unbind shouldn't + * be invoked until all the other callbacks are finished. + */ + while (dum->callback_usage > 0) { + spin_unlock_irqrestore(&dum->lock, flags); + usleep_range(1000, 2000); + spin_lock_irqsave(&dum->lock, flags); + } + } spin_unlock_irqrestore(&dum->lock, flags); usb_hcd_poll_rh_status(dummy_hcd_to_hcd(dum_hcd)); @@ -1015,14 +1030,6 @@ static int dummy_udc_stop(struct usb_gad spin_lock_irq(&dum->lock); dum->ints_enabled = 0; stop_activity(dum); - - /* emulate synchronize_irq(): wait for callbacks to finish */ - while (dum->callback_usage > 0) { - spin_unlock_irq(&dum->lock); - usleep_range(1000, 2000); - spin_lock_irq(&dum->lock); - } - dum->driver = NULL; spin_unlock_irq(&dum->lock);