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Mon, 02 Dec 2024 06:56:10 -0800 (PST) X-Google-Smtp-Source: AGHT+IEJQaJW0zre9XIeROgYN/FJjTnxYGPO36rn6GiEgfSijb3+9BRwxJ39xLZ6IITHDMcGsy9uQA== X-Received: by 2002:a17:906:329a:b0:aa5:1d08:dacf with SMTP id a640c23a62f3a-aa580f01a6amr2029060066b.13.1733151370143; Mon, 02 Dec 2024 06:56:10 -0800 (PST) Received: from [10.40.98.157] ([78.108.130.194]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-aa5998e64a8sm514473266b.130.2024.12.02.06.56.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 02 Dec 2024 06:56:09 -0800 (PST) Message-ID: <38121061-452d-486a-80e5-e4cda0ab9071@redhat.com> Date: Mon, 2 Dec 2024 15:56:08 +0100 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 2/5] media: uvcvideo: Remove dangling pointers To: Ricardo Ribalda Cc: Laurent Pinchart , Mauro Carvalho Chehab , Guennadi Liakhovetski , Hans Verkuil , Mauro Carvalho Chehab , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20241202-uvc-fix-async-v5-0-6658c1fe312b@chromium.org> <20241202-uvc-fix-async-v5-2-6658c1fe312b@chromium.org> <79da5e62-acb0-4bf5-a1c0-f2000fae0167@redhat.com> Content-Language: en-US From: Hans de Goede In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi, On 2-Dec-24 3:49 PM, Ricardo Ribalda wrote: > Hi Hans > > > On Mon, 2 Dec 2024 at 15:44, Hans de Goede wrote: >> >> Hi, >> >> On 2-Dec-24 3:24 PM, 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 | 52 ++++++++++++++++++++++++++++++++++++++-- >>> drivers/media/usb/uvc/uvc_v4l2.c | 2 ++ >>> drivers/media/usb/uvc/uvcvideo.h | 9 ++++++- >>> 3 files changed, 60 insertions(+), 3 deletions(-) >>> >>> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c >>> index 9a80a7d8e73a..af1e38f5c6e9 100644 >>> --- a/drivers/media/usb/uvc/uvc_ctrl.c >>> +++ b/drivers/media/usb/uvc/uvc_ctrl.c >>> @@ -1579,6 +1579,37 @@ static void uvc_ctrl_send_slave_event(struct uvc_video_chain *chain, >>> uvc_ctrl_send_event(chain, handle, ctrl, mapping, val, changes); >>> } >>> >>> +static void uvc_ctrl_get_handle(struct uvc_fh *handle, struct uvc_control *ctrl) >>> +{ >>> + lockdep_assert_held(&handle->chain->ctrl_mutex); >>> + >>> + if (ctrl->handle) >>> + dev_warn_ratelimited(&handle->stream->dev->udev->dev, >>> + "UVC non compliance: Setting an async control with a pending operation."); >>> + >>> + if (handle == ctrl->handle) >>> + return; >>> + >>> + if (ctrl->handle) >>> + ctrl->handle->pending_async_ctrls--; >>> + >>> + ctrl->handle = handle; >>> + handle->pending_async_ctrls++; >>> +} >> >> Maybe simplify this to: > > I do not think that we can do that simplification. > > If we do that, the original file handle `pending_async_ctrls` value > will be out of sync. Ah good point, I missed that the -- and ++ are done on 2 potentially different handles. Regards, Hans >> static void uvc_ctrl_get_handle(struct uvc_fh *handle, struct uvc_control *ctrl) >> { >> lockdep_assert_held(&handle->chain->ctrl_mutex); >> >> if (!ctrl->handle) >> handle->pending_async_ctrls++; >> else >> dev_warn_ratelimited(&handle->stream->dev->udev->dev, >> "UVC non compliance: Setting an async control with a pending operation."); >> >> ctrl->handle = handle; >> } >> >> ? >> >> Otherwise the patch looks good to me: >> >> Reviewed-by: Hans de Goede > > > >> >> Regards, >> >> Hans >> >> >> >> >>> +static void uvc_ctrl_put_handle(struct uvc_fh *handle, struct uvc_control *ctrl) >>> +{ >>> + lockdep_assert_held(&handle->chain->ctrl_mutex); >>> + >>> + if (ctrl->handle != handle) /* Nothing to do here.*/ >>> + return; >>> + >>> + ctrl->handle = NULL; >>> + if (WARN_ON(!handle->pending_async_ctrls)) >>> + return; >>> + handle->pending_async_ctrls--; >>> +} >>> + >>> void uvc_ctrl_status_event(struct uvc_video_chain *chain, >>> struct uvc_control *ctrl, const u8 *data) >>> { >>> @@ -1589,7 +1620,8 @@ void uvc_ctrl_status_event(struct uvc_video_chain *chain, >>> mutex_lock(&chain->ctrl_mutex); >>> >>> handle = ctrl->handle; >>> - ctrl->handle = NULL; >>> + if (handle) >>> + uvc_ctrl_put_handle(handle, ctrl); >>> >>> list_for_each_entry(mapping, &ctrl->info.mappings, list) { >>> s32 value = __uvc_ctrl_get_value(mapping, data); >>> @@ -1865,7 +1897,7 @@ static int uvc_ctrl_commit_entity(struct uvc_device *dev, >>> >>> if (!rollback && handle && >>> ctrl->info.flags & UVC_CTRL_FLAG_ASYNCHRONOUS) >>> - ctrl->handle = handle; >>> + uvc_ctrl_get_handle(handle, ctrl); >>> } >>> >>> return 0; >>> @@ -2774,6 +2806,22 @@ 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) >>> + uvc_ctrl_put_handle(handle, &entity->controls[i]); >>> + >>> + 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..92ecdd188587 100644 >>> --- a/drivers/media/usb/uvc/uvcvideo.h >>> +++ b/drivers/media/usb/uvc/uvcvideo.h >>> @@ -337,7 +337,11 @@ 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, >>> + * ctrl.handle and >>> + * uvc_fh.pending_async_ctrls >>> + */ >>> >>> struct v4l2_prio_state prio; /* V4L2 priority state */ >>> u32 caps; /* V4L2 chain-wide caps */ >>> @@ -612,6 +616,7 @@ 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 +802,8 @@ 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); >>> >> > >