From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A688B1C2439; Thu, 28 Nov 2024 22:28:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732832901; cv=none; b=HX3Urbv58gGj3vZQRBQOoY/j1J+ouLpxAOLdA3Ae8R5QQzToZ1O1uTJ1WAXhsZPmBnPCLwZP9jEScSQLJM4Kblqr3m0O3NmpSJsFgyuMim3AiLSYALTM9T4+0qIoJNKpS8YFRG3orzylo+GDUsj6NnhHoKG9HymOMUJzIzpLt5U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732832901; c=relaxed/simple; bh=PuRA/oKcYO/DaboUdRBHzaDmIdxsINe42WiTaGHCyPM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=gaobSJx+QHiAZcKJTAbKStGIGZF0LxRV3eO2BDMACDEFoav2PXdJ/ARCqfALchXL+Y6bWj2vTISgtwVAKIT2dmKtLXUaBAh0LpGdlcb9pu9Kbi8B75iRYMbkGgllvjf1WfOU5it91GpeBTzX/mLBUW5YtQyLdYDs8u81I8KcZwM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=kZrKO78U; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="kZrKO78U" Received: from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi [81.175.209.231]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 88E7F526; Thu, 28 Nov 2024 23:27:53 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1732832873; bh=PuRA/oKcYO/DaboUdRBHzaDmIdxsINe42WiTaGHCyPM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=kZrKO78UEj4pufWAhiGdv3IysU4Pw8iykfTtTKGj+b89rxg88S0joZhxfXyoJMNdL HazIcUHjB9VWxaGvikj5cC+CSEMl0GEnG3BSx076e22mHjqgR/+j+d+U1+TNLp2Ycn /abMxqs8wcLNGEPvc6/jo0aFF8yqUUAMP6URXLmA= Date: Fri, 29 Nov 2024 00:28:07 +0200 From: Laurent Pinchart To: Ricardo Ribalda Cc: Hans de Goede , Mauro Carvalho Chehab , Guennadi Liakhovetski , Mauro Carvalho Chehab , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2 1/4] media: uvcvideo: Remove dangling pointers Message-ID: <20241128222807.GG25731@pendragon.ideasonboard.com> References: <20241127-uvc-fix-async-v2-0-510aab9570dd@chromium.org> <20241127-uvc-fix-async-v2-1-510aab9570dd@chromium.org> <20241128221649.GE25731@pendragon.ideasonboard.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On Thu, Nov 28, 2024 at 11:25:25PM +0100, Ricardo Ribalda wrote: > On Thu, 28 Nov 2024 at 23:17, Laurent Pinchart wrote: > > On Wed, Nov 27, 2024 at 12:14:49PM +0000, Ricardo Ribalda wrote: > > > When an async control is written, we copy a pointer to the file handle > > > that started the operation. That pointer will be used when the device is > > > done. Which could be anytime in the future. > > > > > > If the user closes that file descriptor, its structure will be freed, > > > and there will be one dangling pointer per pending async control, that > > > the driver will try to use. > > > > > > Clean all the dangling pointers during release(). > > > > > > To avoid adding a performance penalty in the most common case (no async > > > operation). A counter has been introduced with some logic to make sure > > > > s/). A/), a/ > > > > > that it is properly handled. > > > > > > Cc: stable@vger.kernel.org > > > Fixes: e5225c820c05 ("media: uvcvideo: Send a control event when a Control Change interrupt arrives") > > > Signed-off-by: Ricardo Ribalda > > > --- > > > drivers/media/usb/uvc/uvc_ctrl.c | 38 ++++++++++++++++++++++++++++++++++++-- > > > drivers/media/usb/uvc/uvc_v4l2.c | 2 ++ > > > drivers/media/usb/uvc/uvcvideo.h | 8 +++++++- > > > 3 files changed, 45 insertions(+), 3 deletions(-) > > > > > > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c > > > index 4fe26e82e3d1..b6af4ff92cbd 100644 > > > --- a/drivers/media/usb/uvc/uvc_ctrl.c > > > +++ b/drivers/media/usb/uvc/uvc_ctrl.c > > > @@ -1589,7 +1589,12 @@ void uvc_ctrl_status_event(struct uvc_video_chain *chain, > > > > How about adding > > SGTM. > > > > > static void uvc_ctrl_set_handle(struct uvc_control *ctrl, uvc_fh *handle) > > { > > if (handle) { > > if (!ctrl->handle) > > handle->pending_async_ctrls++; > > ctrl->handle = handle; > > } else if (ctrl->handle) { > > ctrl->handle = NULL; > > if (!WARN_ON(!handle->pending_async_ctrls)) > > Unless you think otherwise. I will make this: > > WARN_ON(!handle->pending_async_ctrls); > if (handle->pending_async_ctrls) > handle->pending_async_ctrls--; I'm fine with that, I went back and forth between the two. > The double negation is difficult to read. I am pretty sure the > compiler will do its magic and merge the two checks. > > > handle->pending_async_ctrls--; > > } > > } > > > > > mutex_lock(&chain->ctrl_mutex); > > > > > > handle = ctrl->handle; > > > - ctrl->handle = NULL; > > > + if (handle) { > > > + ctrl->handle = NULL; > > > + WARN_ON(!handle->pending_async_ctrls); > > > + if (handle->pending_async_ctrls) > > > + handle->pending_async_ctrls--; > > > + } > > > > This would become > > > > handle = ctrl->handle; > > uvc_ctrl_set_handle(ctrl, NULL); > > > > > > > > list_for_each_entry(mapping, &ctrl->info.mappings, list) { > > > s32 value = __uvc_ctrl_get_value(mapping, data); > > > @@ -2046,8 +2051,11 @@ int uvc_ctrl_set(struct uvc_fh *handle, > > > mapping->set(mapping, value, > > > uvc_ctrl_data(ctrl, UVC_CTRL_DATA_CURRENT)); > > > > > > - if (ctrl->info.flags & UVC_CTRL_FLAG_ASYNCHRONOUS) > > > + if (ctrl->info.flags & UVC_CTRL_FLAG_ASYNCHRONOUS) { > > > + if (!ctrl->handle) > > > + handle->pending_async_ctrls++; > > > ctrl->handle = handle; > > > + } > > > > Here > > > > if (ctrl->info.flags & UVC_CTRL_FLAG_ASYNCHRONOUS) > > uvc_ctrl_set_handle(ctrl, handle); > > > > > > > > ctrl->dirty = 1; > > > ctrl->modified = 1; > > > @@ -2770,6 +2778,32 @@ int uvc_ctrl_init_device(struct uvc_device *dev) > > > return 0; > > > } > > > > > > +void uvc_ctrl_cleanup_fh(struct uvc_fh *handle) > > > +{ > > > + struct uvc_entity *entity; > > > + > > > + guard(mutex)(&handle->chain->ctrl_mutex); > > > + > > > + if (!handle->pending_async_ctrls) > > > + return; > > > + > > > + list_for_each_entry(entity, &handle->chain->dev->entities, list) { > > > + for (unsigned int i = 0; i < entity->ncontrols; ++i) { > > > + struct uvc_control *ctrl = &entity->controls[i]; > > > + > > > + if (ctrl->handle != handle) > > > + continue; > > > + > > > + ctrl->handle = NULL; > > > + if (WARN_ON(!handle->pending_async_ctrls)) > > > + continue; > > > + handle->pending_async_ctrls--; > > > > And here > > > > uvc_ctrl_set_handle(ctrl, NULL); > > > > It seems less error-prone to centralize the logic. I'd add a > > lockdep_assert() in uvc_ctrl_set_handle(), but there's no easy access to > > the chain there. > > > > > + } > > > + } > > > + > > > + WARN_ON(handle->pending_async_ctrls); > > > +} > > > + > > > /* > > > * Cleanup device controls. > > > */ > > > diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c > > > index 97c5407f6603..b425306a3b8c 100644 > > > --- a/drivers/media/usb/uvc/uvc_v4l2.c > > > +++ b/drivers/media/usb/uvc/uvc_v4l2.c > > > @@ -652,6 +652,8 @@ static int uvc_v4l2_release(struct file *file) > > > > > > uvc_dbg(stream->dev, CALLS, "%s\n", __func__); > > > > > > + uvc_ctrl_cleanup_fh(handle); > > > + > > > /* Only free resources if this is a privileged handle. */ > > > if (uvc_has_privileges(handle)) > > > uvc_queue_release(&stream->queue); > > > diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h > > > index 07f9921d83f2..c68659b70221 100644 > > > --- a/drivers/media/usb/uvc/uvcvideo.h > > > +++ b/drivers/media/usb/uvc/uvcvideo.h > > > @@ -337,7 +337,10 @@ struct uvc_video_chain { > > > struct uvc_entity *processing; /* Processing unit */ > > > struct uvc_entity *selector; /* Selector unit */ > > > > > > - struct mutex ctrl_mutex; /* Protects ctrl.info */ > > > + struct mutex ctrl_mutex; /* > > > + * Protects ctrl.info and > > > + * uvc_fh.pending_async_ctrls > > > + */ > > > > > > struct v4l2_prio_state prio; /* V4L2 priority state */ > > > u32 caps; /* V4L2 chain-wide caps */ > > > @@ -612,6 +615,7 @@ struct uvc_fh { > > > struct uvc_video_chain *chain; > > > struct uvc_streaming *stream; > > > enum uvc_handle_state state; > > > + unsigned int pending_async_ctrls; > > > }; > > > > > > struct uvc_driver { > > > @@ -797,6 +801,8 @@ int uvc_ctrl_is_accessible(struct uvc_video_chain *chain, u32 v4l2_id, > > > int uvc_xu_ctrl_query(struct uvc_video_chain *chain, > > > struct uvc_xu_control_query *xqry); > > > > > > +void uvc_ctrl_cleanup_fh(struct uvc_fh *handle); > > > + > > > /* Utility functions */ > > > struct usb_host_endpoint *uvc_find_endpoint(struct usb_host_interface *alts, > > > u8 epaddr); -- Regards, Laurent Pinchart