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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6F45EC433FE for ; Sat, 7 May 2022 14:27:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1376812AbiEGObH (ORCPT ); Sat, 7 May 2022 10:31:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36238 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234096AbiEGObF (ORCPT ); Sat, 7 May 2022 10:31:05 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E97722DFC; Sat, 7 May 2022 07:27:18 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 79108608C3; Sat, 7 May 2022 14:27:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6414AC385A5; Sat, 7 May 2022 14:27:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1651933637; bh=8jXCjBGJJPxlr9V8Zv0vyc5vMNnF06uj4+zEg0fhpsc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=A3vs/lC4UGjixwmTZ9Oc+ZggDjdz1Rio+dfRcyFx7B9JZjuC7EHZZPCA20XyTJCu9 YCpuNVkfTX/txbkqNDZISV9INKPVYCJjLXJTUnJP1Va2ekU3OnXEAjfu91Z5UwOT+K it/aFKi6szvE0V0mqKFCApv/KF/ECV+RzSz2dQsc= Date: Sat, 7 May 2022 16:27:14 +0200 From: Greg KH To: Schspa Shi Cc: andreyknvl@gmail.com, balbi@kernel.org, jj251510319013@gmail.com, stern@rowland.harvard.edu, jannh@google.com, Julia.Lawall@inria.fr, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+dc7c3ca638e773db07f6@syzkaller.appspotmail.com Subject: Re: [PATCH] usb: gadget: fix race when gadget driver register via ioctl Message-ID: References: <20220507120851.29948-1-schspa@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220507120851.29948-1-schspa@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, May 07, 2022 at 08:08:51PM +0800, Schspa Shi wrote: > The usb_gadget_register_driver doesn't have inside locks to protect the > driver, and If there is two threads are registered at the same time via > the ioctl syscall, the system will crash as syzbot reported. > > Call trace as: > driver_register+0x220/0x3a0 drivers/base/driver.c:171 > usb_gadget_register_driver_owner+0xfb/0x1e0 > drivers/usb/gadget/udc/core.c:1546 > raw_ioctl_run drivers/usb/gadget/legacy/raw_gadget.c:513 [inline] > raw_ioctl+0x1883/0x2730 drivers/usb/gadget/legacy/raw_gadget.c:1220 > > This routine allows two processes to register the same driver instance > via ioctl syscall. which lead to a race condition. > > We can fix it by adding a driver_lock to avoid double register. > > Reported-by: syzbot+dc7c3ca638e773db07f6@syzkaller.appspotmail.com > Link: https://lore.kernel.org/all/000000000000e66c2805de55b15a@google.com/ > > Signed-off-by: Schspa Shi > --- > drivers/usb/gadget/legacy/raw_gadget.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/usb/gadget/legacy/raw_gadget.c b/drivers/usb/gadget/legacy/raw_gadget.c > index b3be8db1ff63..d7ff9c2b5397 100644 > --- a/drivers/usb/gadget/legacy/raw_gadget.c > +++ b/drivers/usb/gadget/legacy/raw_gadget.c > @@ -155,7 +155,9 @@ struct raw_dev { > spinlock_t lock; > > const char *udc_name; > + /* Protected by driver_lock for reentrant registration */ > struct usb_gadget_driver driver; > + struct mutex driver_lock; Why are you adding another lock here? What's wrong with the existing lock in this structure that requires an additional one? > > /* Reference to misc device: */ > struct device *dev; > @@ -188,6 +190,8 @@ static struct raw_dev *dev_new(void) > spin_lock_init(&dev->lock); > init_completion(&dev->ep0_done); > raw_event_queue_init(&dev->queue); > + mutex_init(&dev->driver_lock); > + > return dev; > } > > @@ -398,7 +402,9 @@ static int raw_release(struct inode *inode, struct file *fd) > spin_unlock_irqrestore(&dev->lock, flags); > > if (unregister) { > + mutex_lock(&dev->driver_lock); > ret = usb_gadget_unregister_driver(&dev->driver); > + mutex_unlock(&dev->driver_lock); > if (ret != 0) > dev_err(dev->dev, > "usb_gadget_unregister_driver() failed with %d\n", > @@ -510,7 +516,9 @@ static int raw_ioctl_run(struct raw_dev *dev, unsigned long value) > } > spin_unlock_irqrestore(&dev->lock, flags); > > + mutex_lock(&dev->driver_lock); > ret = usb_gadget_register_driver(&dev->driver); > + mutex_unlock(&dev->driver_lock); How can unregister race with register? What ioctl is causing this race? What userspace program is doing this? Only one userspace program should be accessing this at once, right? confused, greg k-h