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 2335E1C3043; Thu, 28 Nov 2024 20:51:42 +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=1732827104; cv=none; b=GQK26HCIX/aydIuuLDeouLBUs1wZgS5HP/sF9tzAudsnmF0AfK2/1Ge5gw2z6p6MGaOy3ief32Z1Jd9EZhgGxy5UXNPfVUTMO5AVtVrswSlIeL4O9wmdvjo+gOFk9yKCXnMZmhRYybPU9xMON7fTP2FG3IKu7JqTiNTDWJGbtYc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732827104; c=relaxed/simple; bh=XYNdnQsuOuENwVuFCQPH8d/EawCzR1g6/sMu75B/Kkc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=LlMBczmR0D7bzWhJW+z6ur5IUIDXh8QDv5lAyYJDczhYg4Uq+n/KfWEnMcPYVsn0+eHnIxoshm5jXWeTuZVr6oamjrkS7PhdvQFrYwjx2GaeeDz9/ysppm5thxGYUrbhpRphwNZd2L+oMyTjdL7Vxcyde4FkpARZiw/0XyQ/Y7Q= 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=L1b1CFBL; 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="L1b1CFBL" Received: from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi [81.175.209.231]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 25BD859D; Thu, 28 Nov 2024 21:51:17 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1732827077; bh=XYNdnQsuOuENwVuFCQPH8d/EawCzR1g6/sMu75B/Kkc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=L1b1CFBLVQPZy6/NOYjesoREw1wx4pl/GxX/VOVfaKs8uPCSVhfTQvtC+L5+LKvvK 3ZKhG961L6+7ljnOt1INPdPsHiG4HwwikiGtplnOLfVtqmg4CkYDPvor4wQEZDSpxO iW91L1o+5gEzG9Jty/PZvE40g1BuynFK8ALm6LP8= Date: Thu, 28 Nov 2024 22:51:30 +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 2/2] media: uvcvideo: Remove dangling pointers Message-ID: <20241128205130.GC25731@pendragon.ideasonboard.com> References: <20241127-uvc-fix-async-v1-0-eb8722531b8c@chromium.org> <20241127-uvc-fix-async-v1-2-eb8722531b8c@chromium.org> <20241127093506.GE31095@pendragon.ideasonboard.com> Precedence: bulk X-Mailing-List: stable@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 Wed, Nov 27, 2024 at 11:23:48AM +0100, Ricardo Ribalda wrote: > On Wed, 27 Nov 2024 at 10:35, Laurent Pinchart wrote: > > On Wed, Nov 27, 2024 at 07:46:11AM +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 > > > 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 | 40 ++++++++++++++++++++++++++++++++++++++-- > > > drivers/media/usb/uvc/uvc_v4l2.c | 2 ++ > > > drivers/media/usb/uvc/uvcvideo.h | 3 +++ > > > 3 files changed, 43 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c > > > index 5d3a28edf7f0..51a53ad25e9c 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, > > > 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--; > > > + } > > > > There's at least one other location where ctrl->handle is reset to NULL. > > That assignment is not needed. I added a patch to remove it in the next version. > > > > > > > list_for_each_entry(mapping, &ctrl->info.mappings, list) { > > > s32 value = __uvc_ctrl_get_value(mapping, data); > > > @@ -2050,8 +2055,11 @@ 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; > > > > Is this protected by ctrl_mutex ? > > yes, uvc_ctrl_set is only called by uvc_ioctl_s_try_ext_ctrls that > calls uvc_ctrl_begin You're right. I think I figured out after writing this part of the review, and forgot to delete it. Sorry. > I will send another patch to add an annotation to the function to make > it explicit. > > > Please be careful about locking and race conditions, taking the time to > > double check will help getting your patches merged faster. > > > > > + } > > > > > > ctrl->dirty = 1; > > > ctrl->modified = 1; > > > @@ -2774,6 +2782,34 @@ 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) { > > > + int i; > > > > unsigned int > > > > I wonder if these days you could event write > > > > for (unsigned int i = 0; i < entity->ncontrols; ++i) { > > > > > + > > > + for (i = 0; i < entity->ncontrols; ++i) { > > > + struct uvc_control *ctrl = &entity->controls[i]; > > > + > > > + if (!ctrl->handle || ctrl->handle != handle) > > > > Given that handle can't be null, you can write > > > > if (ctrl->handle != handle) > > > > > + continue; > > > + > > > + ctrl->handle = NULL; > > > + if (WARN_ON(!handle->pending_async_ctrls)) > > > + continue; > > > > Is this needed ? If we find more controls for this handle than > > pending_async_ctrls, decrementing it below 0 will case the WARN_ON() at > > the end of this function to trigger, isn't that enough ? > > I want to know if the warning is triggered because I have too many > pending_async_ctrls or too little. You could also print the value of pending_async_ctrls at the end, it would give you that information, and tell you how many you're missing. Not a big deal, and I don't expect that warning to be triggered. > > > + handle->pending_async_ctrls--; > > > + } > > > + } > > > + > > > + 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..2f8a9c48e32a 100644 > > > --- a/drivers/media/usb/uvc/uvcvideo.h > > > +++ b/drivers/media/usb/uvc/uvcvideo.h > > > @@ -612,6 +612,7 @@ struct uvc_fh { > > > struct uvc_video_chain *chain; > > > struct uvc_streaming *stream; > > > enum uvc_handle_state state; > > > + unsigned int pending_async_ctrls; /* Protected by ctrl_mutex. */ > > > > The kernel does it the other way around, it lists in the documentation > > of the lock what data it protects. > > > > > }; > > > > > > struct uvc_driver { > > > @@ -797,6 +798,8 @@ 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