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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=no 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 C91FDECE58E for ; Mon, 7 Oct 2019 15:09:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A9EA52070B for ; Mon, 7 Oct 2019 15:09:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728590AbfJGPJy (ORCPT ); Mon, 7 Oct 2019 11:09:54 -0400 Received: from iolanthe.rowland.org ([192.131.102.54]:60272 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1727711AbfJGPJy (ORCPT ); Mon, 7 Oct 2019 11:09:54 -0400 Received: (qmail 4356 invoked by uid 2102); 7 Oct 2019 11:09:53 -0400 Received: from localhost (sendmail-bs@127.0.0.1) by localhost with SMTP; 7 Oct 2019 11:09:53 -0400 Date: Mon, 7 Oct 2019 11:09:53 -0400 (EDT) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Mauro Carvalho Chehab , Hans Verkuil cc: linux-media@vger.kernel.org, USB list , Subject: [PATCH 2/2 RESEND] media: usbvision: Fix races among open, close, and disconnect Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Visual inspection of the usbvision driver shows that it suffers from three races between its open, close, and disconnect handlers. In particular, the driver is careful to update its usbvision->user and usbvision->remove_pending flags while holding the private mutex, but: usbvision_v4l2_close() and usbvision_radio_close() don't hold the mutex while they check the value of usbvision->remove_pending; usbvision_disconnect() doesn't hold the mutex while checking the value of usbvision->user; and also, usbvision_v4l2_open() and usbvision_radio_open() don't check whether the device has been unplugged before allowing the user to open the device files. Each of these can potentially lead to usbvision_release() being called twice and use-after-free errors. This patch fixes the races by reading the flags while the mutex is still held and checking for pending removes before allowing an open to succeed. Signed-off-by: Alan Stern CC: --- [as1920] drivers/media/usb/usbvision/usbvision-video.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) Index: usb-devel/drivers/media/usb/usbvision/usbvision-video.c =================================================================== --- usb-devel.orig/drivers/media/usb/usbvision/usbvision-video.c +++ usb-devel/drivers/media/usb/usbvision/usbvision-video.c @@ -314,6 +314,10 @@ static int usbvision_v4l2_open(struct fi if (mutex_lock_interruptible(&usbvision->v4l2_lock)) return -ERESTARTSYS; + if (usbvision->remove_pending) { + err_code = -ENODEV; + goto unlock; + } if (usbvision->user) { err_code = -EBUSY; } else { @@ -377,6 +381,7 @@ unlock: static int usbvision_v4l2_close(struct file *file) { struct usb_usbvision *usbvision = video_drvdata(file); + int r; PDEBUG(DBG_IO, "close"); @@ -391,9 +396,10 @@ static int usbvision_v4l2_close(struct f usbvision_scratch_free(usbvision); usbvision->user--; + r = usbvision->remove_pending; mutex_unlock(&usbvision->v4l2_lock); - if (usbvision->remove_pending) { + if (r) { printk(KERN_INFO "%s: Final disconnect\n", __func__); usbvision_release(usbvision); return 0; @@ -1076,6 +1082,11 @@ static int usbvision_radio_open(struct f if (mutex_lock_interruptible(&usbvision->v4l2_lock)) return -ERESTARTSYS; + + if (usbvision->remove_pending) { + err_code = -ENODEV; + goto out; + } err_code = v4l2_fh_open(file); if (err_code) goto out; @@ -1108,6 +1119,7 @@ out: static int usbvision_radio_close(struct file *file) { struct usb_usbvision *usbvision = video_drvdata(file); + int r; PDEBUG(DBG_IO, ""); @@ -1121,9 +1133,10 @@ static int usbvision_radio_close(struct usbvision_audio_off(usbvision); usbvision->radio = 0; usbvision->user--; + r = usbvision->remove_pending; mutex_unlock(&usbvision->v4l2_lock); - if (usbvision->remove_pending) { + if (r) { printk(KERN_INFO "%s: Final disconnect\n", __func__); v4l2_fh_release(file); usbvision_release(usbvision); @@ -1555,6 +1568,7 @@ err_usb: static void usbvision_disconnect(struct usb_interface *intf) { struct usb_usbvision *usbvision = to_usbvision(usb_get_intfdata(intf)); + int u; PDEBUG(DBG_PROBE, ""); @@ -1571,13 +1585,14 @@ static void usbvision_disconnect(struct v4l2_device_disconnect(&usbvision->v4l2_dev); usbvision_i2c_unregister(usbvision); usbvision->remove_pending = 1; /* Now all ISO data will be ignored */ + u = usbvision->user; usb_put_dev(usbvision->dev); usbvision->dev = NULL; /* USB device is no more */ mutex_unlock(&usbvision->v4l2_lock); - if (usbvision->user) { + if (u) { printk(KERN_INFO "%s: In use, disconnect pending\n", __func__); wake_up_interruptible(&usbvision->wait_frame);