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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E16AAC433FE for ; Tue, 26 Oct 2021 21:51:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CC86061073 for ; Tue, 26 Oct 2021 21:51:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239723AbhJZVxk (ORCPT ); Tue, 26 Oct 2021 17:53:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44656 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239706AbhJZVxh (ORCPT ); Tue, 26 Oct 2021 17:53:37 -0400 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0CFBEC061570; Tue, 26 Oct 2021 14:51:13 -0700 (PDT) Received: from pendragon.ideasonboard.com (62-78-145-57.bb.dnainternet.fi [62.78.145.57]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 1471D3F0; Tue, 26 Oct 2021 23:51:10 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1635285070; bh=nrejLrqebeFZ6uqJmuowbCLTFPqWxMstNwb5FIhCx34=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=EYZYX0JpMoyFYiT1HGuTbclLHei5CLtJvu+pPeBso7QBvg52Kki5PJS3AGSeMUM3g kpWkj/vXoHupgmOJxoiLVGOab2Pi6B+UpChcmmBz7pMmdYpqyDYhaU/FbH4aAZr2Aq LecS/ATO3DGeqbelKaqMNS+YPpCFdWwUo7cLmEpI= Date: Wed, 27 Oct 2021 00:50:46 +0300 From: Laurent Pinchart To: Johan Hovold Cc: Kieran Bingham , Mauro Carvalho Chehab , linux-media@vger.kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] media: uvcvideo: fix division by zero at stream start Message-ID: References: <20211026095511.26673-1-johan@kernel.org> <163524570516.1184428.14632987312253060787@Monstersaurus> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Johan, On Tue, Oct 26, 2021 at 02:06:55PM +0200, Johan Hovold wrote: > On Tue, Oct 26, 2021 at 02:15:20PM +0300, Laurent Pinchart wrote: > > On Tue, Oct 26, 2021 at 11:55:05AM +0100, Kieran Bingham wrote: > > > Quoting Johan Hovold (2021-10-26 10:55:11) > > > > Add the missing bulk-endpoint max-packet sanity check to probe() to > > > > avoid division by zero in uvc_alloc_urb_buffers() in case a malicious > > > > device has broken descriptors (or when doing descriptor fuzz testing). > > > > > > > > Note that USB core will reject URBs submitted for endpoints with zero > > > > wMaxPacketSize but that drivers doing packet-size calculations still > > > > need to handle this (cf. commit 2548288b4fb0 ("USB: Fix: Don't skip > > > > endpoint descriptors with maxpacket=0")). > > > > > > > > Fixes: c0efd232929c ("V4L/DVB (8145a): USB Video Class driver") > > > > Cc: stable@vger.kernel.org # 2.6.26 > > > > Signed-off-by: Johan Hovold > > > > --- > > > > drivers/media/usb/uvc/uvc_video.c | 4 ++++ > > > > 1 file changed, 4 insertions(+) > > > > > > > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c > > > > index e16464606b14..85ac5c1081b6 100644 > > > > --- a/drivers/media/usb/uvc/uvc_video.c > > > > +++ b/drivers/media/usb/uvc/uvc_video.c > > > > @@ -1958,6 +1958,10 @@ static int uvc_video_start_transfer(struct uvc_streaming *stream, > > > > if (ep == NULL) > > > > return -EIO; > > > > > > > > + /* Reject broken descriptors. */ > > > > + if (usb_endpoint_maxp(&ep->desc) == 0) > > > > + return -EIO; > > > > > > Is there any value in identifying this with a specific return code like > > > -ENODATA? > > > > Going one step further, wouldn't it be better to fail probe() for those > > devices ? > > This is not how the driver works today. Look at the "return -EIO" just > above in case the expected endpoint is missing. And similarly for the > isochronous case for which zero wMaxPacket isn't handled until > uvc_video_start_transfer() either (a few lines further up still). That's a good point, it wouldn't be reasonable to ask you to fix all that :-) > Note however the copy-paste error in the commit message mentioning > probe(), which is indeed where this would typically be handled. > > Do you want me to resend or can you change > > s/probe()/uvc_video_start_transfer()/ > > in the commit message when applying if you think this is acceptable as > is? I can fix this when applying. Reviewed-by: Laurent Pinchart -- Regards, Laurent Pinchart