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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 8F886C48BC2 for ; Mon, 21 Jun 2021 12:09:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7B09B6109F for ; Mon, 21 Jun 2021 12:09:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229968AbhFUMLy (ORCPT ); Mon, 21 Jun 2021 08:11:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54932 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229621AbhFUMLw (ORCPT ); Mon, 21 Jun 2021 08:11:52 -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 B030EC061574; Mon, 21 Jun 2021 05:09:38 -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 980B75A1; Mon, 21 Jun 2021 14:09:36 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1624277376; bh=D5aMC3nKs6AeN78dem+9AycwhE8/FV0A4CCif5//bLM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=A5p81FfzQAS3GzxbMk60HCHztOPPEQYeUAg638qc0fDSphfWmsKkwWpZuIP9+i5GX ONT+PpHelDvOqS1Cvlc5GIPLYT58AqdpEV3h9KRK4YBcrmJbI8uY6py75oR/HfTCji Q0kr/wMdYpIIG0HsQujKv39L8PWrV9Hx1epin5+I= Date: Mon, 21 Jun 2021 15:09:10 +0300 From: Laurent Pinchart To: Mauro Carvalho Chehab Cc: linuxarm@huawei.com, mauro.chehab@huawei.com, Mauro Carvalho Chehab , linux-kernel@vger.kernel.org, linux-media@vger.kernel.org Subject: Re: [PATCH 2/5] media: uvc: don't do DMA on stack Message-ID: References: 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 Mauro, Thank you for the patch. On Mon, Jun 21, 2021 at 01:56:46PM +0200, Mauro Carvalho Chehab wrote: > As warned by smatch: > drivers/media/usb/uvc/uvc_v4l2.c:911 uvc_ioctl_g_input() error: doing dma on the stack (&i) > drivers/media/usb/uvc/uvc_v4l2.c:943 uvc_ioctl_s_input() error: doing dma on the stack (&i) > > those two functions call uvc_query_ctrl passing a pointer to > a data at the DMA stack. those are used to send URBs via > usb_control_msg(). Using DMA stack is not supported and should > not work anymore on modern Linux versions. > > So, use a temporary buffer, allocated together with > struct uvc_video_chain. DMA in a memory location that may share a cache line with something else isn't a great idea either. The buffer should be kmalloc()ed in uvc_ioctl_g_input() and uvc_ioctl_s_input(). > Signed-off-by: Mauro Carvalho Chehab > --- > drivers/media/usb/uvc/uvc_v4l2.c | 10 ++++------ > drivers/media/usb/uvc/uvcvideo.h | 3 +++ > 2 files changed, 7 insertions(+), 6 deletions(-) > > diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c > index 252136cc885c..e60d4675881a 100644 > --- a/drivers/media/usb/uvc/uvc_v4l2.c > +++ b/drivers/media/usb/uvc/uvc_v4l2.c > @@ -900,7 +900,6 @@ static int uvc_ioctl_g_input(struct file *file, void *fh, unsigned int *input) > struct uvc_fh *handle = fh; > struct uvc_video_chain *chain = handle->chain; > int ret; > - u8 i; > > if (chain->selector == NULL || > (chain->dev->quirks & UVC_QUIRK_IGNORE_SELECTOR_UNIT)) { > @@ -910,11 +909,11 @@ static int uvc_ioctl_g_input(struct file *file, void *fh, unsigned int *input) > > ret = uvc_query_ctrl(chain->dev, UVC_GET_CUR, chain->selector->id, > chain->dev->intfnum, UVC_SU_INPUT_SELECT_CONTROL, > - &i, 1); > + &chain->input, 1); > if (ret < 0) > return ret; > > - *input = i - 1; > + *input = chain->input - 1; > return 0; > } > > @@ -923,7 +922,6 @@ static int uvc_ioctl_s_input(struct file *file, void *fh, unsigned int input) > struct uvc_fh *handle = fh; > struct uvc_video_chain *chain = handle->chain; > int ret; > - u32 i; > > ret = uvc_acquire_privileges(handle); > if (ret < 0) > @@ -939,10 +937,10 @@ static int uvc_ioctl_s_input(struct file *file, void *fh, unsigned int input) > if (input >= chain->selector->bNrInPins) > return -EINVAL; > > - i = input + 1; > + chain->input = input + 1; > return uvc_query_ctrl(chain->dev, UVC_SET_CUR, chain->selector->id, > chain->dev->intfnum, UVC_SU_INPUT_SELECT_CONTROL, > - &i, 1); > + &chain->input, 1); > } > > static int uvc_ioctl_queryctrl(struct file *file, void *fh, > diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h > index cce5e38133cd..3c0ed90d6912 100644 > --- a/drivers/media/usb/uvc/uvcvideo.h > +++ b/drivers/media/usb/uvc/uvcvideo.h > @@ -475,6 +475,9 @@ struct uvc_video_chain { > struct mutex ctrl_mutex; /* Protects ctrl.info */ > > struct v4l2_prio_state prio; /* V4L2 priority state */ > + > + u8 input; /* buffer for set/get input */ > + > u32 caps; /* V4L2 chain-wide caps */ > }; > -- Regards, Laurent Pinchart