Currently the set_alt callback immediately disables the endpoint and queues
the v4l2 streamoff event. However, as the streamoff event is processed
asynchronously, it is possible that the video_pump thread attempts to queue
requests to an already disabled endpoint.

This change moves disabling usb endpoint to the end of streamoff event
callback. To be consistent with the actual streaming state, uvc->state
is now toggled between CONNECTED and STREAMING from the v4l2 event
callback only.

Link: https://lore.kernel.org/20230615171558.GK741@pendragon.ideasonboard.com/
Link: https://lore.kernel.org/20230531085544.253363-1-dan.scally@ideasonboard.com/
Signed-off-by: Avichal Rakesh <arakesh@google.com>
---
v1 -> v2: Rebased to ToT and reworded commit message.
v2 -> v3: Fix email threading goof-up

 drivers/usb/gadget/function/f_uvc.c    | 11 +++++------
 drivers/usb/gadget/function/f_uvc.h    |  2 +-
 drivers/usb/gadget/function/uvc.h      |  2 +-
 drivers/usb/gadget/function/uvc_v4l2.c | 21 ++++++++++++++++++---
 4 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/drivers/usb/gadget/function/f_uvc.c b/drivers/usb/gadget/function/f_uvc.c
index faa398109431..75c9f9a3f884 100644
--- a/drivers/usb/gadget/function/f_uvc.c
+++ b/drivers/usb/gadget/function/f_uvc.c
@@ -263,10 +263,13 @@ uvc_function_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
 	return 0;
 }

-void uvc_function_setup_continue(struct uvc_device *uvc)
+void uvc_function_setup_continue(struct uvc_device *uvc, int disable_ep)
 {
 	struct usb_composite_dev *cdev = uvc->func.config->cdev;

+	if (disable_ep && uvc->video.ep) {
+		usb_ep_disable(uvc->video.ep);
+	}
 	usb_composite_setup_continue(cdev);
 }

@@ -337,15 +340,11 @@ uvc_function_set_alt(struct usb_function *f, unsigned interface, unsigned alt)
 		if (uvc->state != UVC_STATE_STREAMING)
 			return 0;

-		if (uvc->video.ep)
-			usb_ep_disable(uvc->video.ep);
-
 		memset(&v4l2_event, 0, sizeof(v4l2_event));
 		v4l2_event.type = UVC_EVENT_STREAMOFF;
 		v4l2_event_queue(&uvc->vdev, &v4l2_event);

-		uvc->state = UVC_STATE_CONNECTED;
-		return 0;
+		return USB_GADGET_DELAYED_STATUS;

 	case 1:
 		if (uvc->state != UVC_STATE_CONNECTED)
diff --git a/drivers/usb/gadget/function/f_uvc.h b/drivers/usb/gadget/function/f_uvc.h
index 1db972d4beeb..e7f9f13f14dc 100644
--- a/drivers/usb/gadget/function/f_uvc.h
+++ b/drivers/usb/gadget/function/f_uvc.h
@@ -11,7 +11,7 @@

 struct uvc_device;

-void uvc_function_setup_continue(struct uvc_device *uvc);
+void uvc_function_setup_continue(struct uvc_device *uvc, int disale_ep);

 void uvc_function_connect(struct uvc_device *uvc);

diff --git a/drivers/usb/gadget/function/uvc.h b/drivers/usb/gadget/function/uvc.h
index 6751de8b63ad..989bc6b4e93d 100644
--- a/drivers/usb/gadget/function/uvc.h
+++ b/drivers/usb/gadget/function/uvc.h
@@ -177,7 +177,7 @@ struct uvc_file_handle {
  * Functions
  */

-extern void uvc_function_setup_continue(struct uvc_device *uvc);
+extern void uvc_function_setup_continue(struct uvc_device *uvc, int disable_ep);
 extern void uvc_function_connect(struct uvc_device *uvc);
 extern void uvc_function_disconnect(struct uvc_device *uvc);

diff --git a/drivers/usb/gadget/function/uvc_v4l2.c b/drivers/usb/gadget/function/uvc_v4l2.c
index 3f0a9795c0d4..3d3469883ed0 100644
--- a/drivers/usb/gadget/function/uvc_v4l2.c
+++ b/drivers/usb/gadget/function/uvc_v4l2.c
@@ -451,7 +451,7 @@ uvc_v4l2_streamon(struct file *file, void *fh, enum v4l2_buf_type type)
 	 * Complete the alternate setting selection setup phase now that
 	 * userspace is ready to provide video frames.
 	 */
-	uvc_function_setup_continue(uvc);
+	uvc_function_setup_continue(uvc, 0);
 	uvc->state = UVC_STATE_STREAMING;

 	return 0;
@@ -463,11 +463,19 @@ uvc_v4l2_streamoff(struct file *file, void *fh, enum v4l2_buf_type type)
 	struct video_device *vdev = video_devdata(file);
 	struct uvc_device *uvc = video_get_drvdata(vdev);
 	struct uvc_video *video = &uvc->video;
+	int ret = 0;

 	if (type != video->queue.queue.type)
 		return -EINVAL;

-	return uvcg_video_enable(video, 0);
+	uvc->state = UVC_STATE_CONNECTED;
+	ret = uvcg_video_enable(video, 0);
+	if (ret < 0) {
+		return ret;
+	}
+
+	uvc_function_setup_continue(uvc, 1);
+	return 0;
 }

 static int
@@ -500,6 +508,14 @@ uvc_v4l2_subscribe_event(struct v4l2_fh *fh,
 static void uvc_v4l2_disable(struct uvc_device *uvc)
 {
 	uvc_function_disconnect(uvc);
+	if (uvc->state == UVC_STATE_STREAMING) {
+		/*
+		 * Drop uvc->state to CONNECTED if it was streaming before.
+		 * This ensures that the usb_requests are no longer queued
+		 * to the controller.
+		 */
+		uvc->state = UVC_STATE_CONNECTED;
+	}
 	uvcg_video_enable(&uvc->video, 0);
 	uvcg_free_buffers(&uvc->video.queue);
 	uvc->func_connected = false;
@@ -647,4 +663,3 @@ const struct v4l2_file_operations uvc_v4l2_fops = {
 	.get_unmapped_area = uvcg_v4l2_get_unmapped_area,
 #endif
 };
-
--
2.42.0.609.gbb76f46606-goog

On Thu, Oct 05, 2023 at 11:08:12AM -0700, Avichal Rakesh wrote:
>Currently the set_alt callback immediately disables the endpoint and queues
>the v4l2 streamoff event. However, as the streamoff event is processed
>asynchronously, it is possible that the video_pump thread attempts to queue
>requests to an already disabled endpoint.
>
>This change moves disabling usb endpoint to the end of streamoff event
>callback. To be consistent with the actual streaming state, uvc->state
>is now toggled between CONNECTED and STREAMING from the v4l2 event
>callback only.
>
>Link: https://lore.kernel.org/20230615171558.GK741@pendragon.ideasonboard.com/
>Link: https://lore.kernel.org/20230531085544.253363-1-dan.scally@ideasonboard.com/
>Signed-off-by: Avichal Rakesh <arakesh@google.com>
>---
>v1 -> v2: Rebased to ToT and reworded commit message.
>v2 -> v3: Fix email threading goof-up
>
> drivers/usb/gadget/function/f_uvc.c    | 11 +++++------
> drivers/usb/gadget/function/f_uvc.h    |  2 +-
> drivers/usb/gadget/function/uvc.h      |  2 +-
> drivers/usb/gadget/function/uvc_v4l2.c | 21 ++++++++++++++++++---
> 4 files changed, 25 insertions(+), 11 deletions(-)
>
>diff --git a/drivers/usb/gadget/function/f_uvc.c b/drivers/usb/gadget/function/f_uvc.c
>index faa398109431..75c9f9a3f884 100644
>--- a/drivers/usb/gadget/function/f_uvc.c
>+++ b/drivers/usb/gadget/function/f_uvc.c
>@@ -263,10 +263,13 @@ uvc_function_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
> 	return 0;
> }
>
>-void uvc_function_setup_continue(struct uvc_device *uvc)
>+void uvc_function_setup_continue(struct uvc_device *uvc, int disable_ep)
> {
> 	struct usb_composite_dev *cdev = uvc->func.config->cdev;
>
>+	if (disable_ep && uvc->video.ep) {
>+		usb_ep_disable(uvc->video.ep);
>+	}

Could you drop the extra braces and add one spare line here.

> 	usb_composite_setup_continue(cdev);
> }
>
>@@ -337,15 +340,11 @@ uvc_function_set_alt(struct usb_function *f, unsigned interface, unsigned alt)
> 		if (uvc->state != UVC_STATE_STREAMING)
> 			return 0;
>
>-		if (uvc->video.ep)
>-			usb_ep_disable(uvc->video.ep);
>-
> 		memset(&v4l2_event, 0, sizeof(v4l2_event));
> 		v4l2_event.type = UVC_EVENT_STREAMOFF;
> 		v4l2_event_queue(&uvc->vdev, &v4l2_event);
>
>-		uvc->state = UVC_STATE_CONNECTED;
>-		return 0;
>+		return USB_GADGET_DELAYED_STATUS;
>
> 	case 1:
> 		if (uvc->state != UVC_STATE_CONNECTED)
>diff --git a/drivers/usb/gadget/function/f_uvc.h b/drivers/usb/gadget/function/f_uvc.h
>index 1db972d4beeb..e7f9f13f14dc 100644
>--- a/drivers/usb/gadget/function/f_uvc.h
>+++ b/drivers/usb/gadget/function/f_uvc.h
>@@ -11,7 +11,7 @@
>
> struct uvc_device;
>
>-void uvc_function_setup_continue(struct uvc_device *uvc);
>+void uvc_function_setup_continue(struct uvc_device *uvc, int disale_ep);
>
> void uvc_function_connect(struct uvc_device *uvc);
>
>diff --git a/drivers/usb/gadget/function/uvc.h b/drivers/usb/gadget/function/uvc.h
>index 6751de8b63ad..989bc6b4e93d 100644
>--- a/drivers/usb/gadget/function/uvc.h
>+++ b/drivers/usb/gadget/function/uvc.h
>@@ -177,7 +177,7 @@ struct uvc_file_handle {
>  * Functions
>  */
>
>-extern void uvc_function_setup_continue(struct uvc_device *uvc);
>+extern void uvc_function_setup_continue(struct uvc_device *uvc, int disable_ep);
> extern void uvc_function_connect(struct uvc_device *uvc);
> extern void uvc_function_disconnect(struct uvc_device *uvc);
>
>diff --git a/drivers/usb/gadget/function/uvc_v4l2.c b/drivers/usb/gadget/function/uvc_v4l2.c
>index 3f0a9795c0d4..3d3469883ed0 100644
>--- a/drivers/usb/gadget/function/uvc_v4l2.c
>+++ b/drivers/usb/gadget/function/uvc_v4l2.c
>@@ -451,7 +451,7 @@ uvc_v4l2_streamon(struct file *file, void *fh, enum v4l2_buf_type type)
> 	 * Complete the alternate setting selection setup phase now that
> 	 * userspace is ready to provide video frames.
> 	 */
>-	uvc_function_setup_continue(uvc);
>+	uvc_function_setup_continue(uvc, 0);
> 	uvc->state = UVC_STATE_STREAMING;
>
> 	return 0;
>@@ -463,11 +463,19 @@ uvc_v4l2_streamoff(struct file *file, void *fh, enum v4l2_buf_type type)
> 	struct video_device *vdev = video_devdata(file);
> 	struct uvc_device *uvc = video_get_drvdata(vdev);
> 	struct uvc_video *video = &uvc->video;
>+	int ret = 0;
>
> 	if (type != video->queue.queue.type)
> 		return -EINVAL;
>
>-	return uvcg_video_enable(video, 0);
>+	uvc->state = UVC_STATE_CONNECTED;
>+	ret = uvcg_video_enable(video, 0);
>+	if (ret < 0) {
>+		return ret;
>+	}

Please drop those extra braces.

>+
>+	uvc_function_setup_continue(uvc, 1);
>+	return 0;
> }
>
> static int
>@@ -500,6 +508,14 @@ uvc_v4l2_subscribe_event(struct v4l2_fh *fh,
> static void uvc_v4l2_disable(struct uvc_device *uvc)
> {
> 	uvc_function_disconnect(uvc);
>+	if (uvc->state == UVC_STATE_STREAMING) {
>+		/*
>+		 * Drop uvc->state to CONNECTED if it was streaming before.
>+		 * This ensures that the usb_requests are no longer queued
>+		 * to the controller.
>+		 */
>+		uvc->state = UVC_STATE_CONNECTED;
>+	}

Could you write the comment above the check
and also remove the extra braces.

> 	uvcg_video_enable(&uvc->video, 0);
> 	uvcg_free_buffers(&uvc->video.queue);
> 	uvc->func_connected = false;
>@@ -647,4 +663,3 @@ const struct v4l2_file_operations uvc_v4l2_fops = {
> 	.get_unmapped_area = uvcg_v4l2_get_unmapped_area,
> #endif
> };
>-
>--
>2.42.0.609.gbb76f46606-goog


With this you can add my:

Reviewed-by: <m.grzeschik@pengutronix.de>

Thanks

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

Currently, the uvc gadget driver allocates all uvc_requests as one array
and deallocates them all when the video stream stops. This includes
de-allocating all the usb_requests associated with those uvc_requests.
This can lead to use-after-free issues if any of those de-allocated
usb_requests were still owned by the usb controller.

This patch is 1 of 2 patches addressing the use-after-free issue.
Instead of bulk allocating all uvc_requests as an array, this patch
allocates uvc_requests one at a time, which should allows for similar
granularity when deallocating the uvc_requests. This patch has no
functional changes other than allocating each uvc_request separately,
and similarly freeing each of them separately.

Link: https://lore.kernel.org/7cd81649-2795-45b6-8c10-b7df1055020d@google.com
Suggested-by: Michael Grzeschik <mgr@pengutronix.de>
Signed-off-by: Avichal Rakesh <arakesh@google.com>
---
v1 -> v2: Rebased to ToT
V2 -> V3: Fix email threading goof-up

 drivers/usb/gadget/function/uvc.h       |  3 +-
 drivers/usb/gadget/function/uvc_video.c | 90 ++++++++++++++-----------
 2 files changed, 51 insertions(+), 42 deletions(-)

diff --git a/drivers/usb/gadget/function/uvc.h b/drivers/usb/gadget/function/uvc.h
index 989bc6b4e93d..993694da0bbc 100644
--- a/drivers/usb/gadget/function/uvc.h
+++ b/drivers/usb/gadget/function/uvc.h
@@ -81,6 +81,7 @@ struct uvc_request {
 	struct sg_table sgt;
 	u8 header[UVCG_REQUEST_HEADER_LEN];
 	struct uvc_buffer *last_buf;
+	struct list_head list;
 };

 struct uvc_video {
@@ -102,7 +103,7 @@ struct uvc_video {

 	/* Requests */
 	unsigned int req_size;
-	struct uvc_request *ureq;
+	struct list_head ureqs; /* all uvc_requests allocated by uvc_video */
 	struct list_head req_free;
 	spinlock_t req_lock;

diff --git a/drivers/usb/gadget/function/uvc_video.c b/drivers/usb/gadget/function/uvc_video.c
index 97d875c27dcf..3c4d286d81c0 100644
--- a/drivers/usb/gadget/function/uvc_video.c
+++ b/drivers/usb/gadget/function/uvc_video.c
@@ -227,6 +227,23 @@ uvc_video_encode_isoc(struct usb_request *req, struct uvc_video *video,
  * Request handling
  */

+static void uvc_video_free_request(struct uvc_request *ureq, struct usb_ep *ep)
+{
+	sg_free_table(&ureq->sgt);
+	if (ureq->req && ep) {
+		usb_ep_free_request(ep, ureq->req);
+		ureq->req = NULL;
+	}
+
+	kfree(ureq->req_buffer);
+	ureq->req_buffer = NULL;
+
+	if (!list_empty(&ureq->list))
+		list_del_init(&ureq->list);
+
+	kfree(ureq);
+}
+
 static int uvcg_video_ep_queue(struct uvc_video *video, struct usb_request *req)
 {
 	int ret;
@@ -299,27 +316,13 @@ uvc_video_complete(struct usb_ep *ep, struct usb_request *req)
 static int
 uvc_video_free_requests(struct uvc_video *video)
 {
-	unsigned int i;
-
-	if (video->ureq) {
-		for (i = 0; i < video->uvc_num_requests; ++i) {
-			sg_free_table(&video->ureq[i].sgt);
-
-			if (video->ureq[i].req) {
-				usb_ep_free_request(video->ep, video->ureq[i].req);
-				video->ureq[i].req = NULL;
-			}
+	struct uvc_request *ureq, *temp;

-			if (video->ureq[i].req_buffer) {
-				kfree(video->ureq[i].req_buffer);
-				video->ureq[i].req_buffer = NULL;
-			}
-		}
-
-		kfree(video->ureq);
-		video->ureq = NULL;
+	list_for_each_entry_safe(ureq, temp, &video->ureqs, list) {
+		uvc_video_free_request(ureq, video->ep);
 	}

+	INIT_LIST_HEAD(&video->ureqs);
 	INIT_LIST_HEAD(&video->req_free);
 	video->req_size = 0;
 	return 0;
@@ -328,6 +331,7 @@ uvc_video_free_requests(struct uvc_video *video)
 static int
 uvc_video_alloc_requests(struct uvc_video *video)
 {
+	struct uvc_request *ureq;
 	unsigned int req_size;
 	unsigned int i;
 	int ret = -ENOMEM;
@@ -338,29 +342,31 @@ uvc_video_alloc_requests(struct uvc_video *video)
 		 * max_t(unsigned int, video->ep->maxburst, 1)
 		 * (video->ep->mult);

-	video->ureq = kcalloc(video->uvc_num_requests, sizeof(struct uvc_request), GFP_KERNEL);
-	if (video->ureq == NULL)
-		return -ENOMEM;
-
-	for (i = 0; i < video->uvc_num_requests; ++i) {
-		video->ureq[i].req_buffer = kmalloc(req_size, GFP_KERNEL);
-		if (video->ureq[i].req_buffer == NULL)
+	INIT_LIST_HEAD(&video->ureqs);
+	for (i = 0; i < video->uvc_num_requests; i++) {
+		ureq = kzalloc(sizeof(struct uvc_request), GFP_KERNEL);
+		if (ureq == NULL)
 			goto error;
+		INIT_LIST_HEAD(&ureq->list);
+		list_add_tail(&ureq->list, &video->ureqs);
+	}

-		video->ureq[i].req = usb_ep_alloc_request(video->ep, GFP_KERNEL);
-		if (video->ureq[i].req == NULL)
+	list_for_each_entry(ureq, &video->ureqs, list) {
+		ureq->req_buffer = kmalloc(req_size, GFP_KERNEL);
+		if (ureq->req_buffer == NULL)
 			goto error;
-
-		video->ureq[i].req->buf = video->ureq[i].req_buffer;
-		video->ureq[i].req->length = 0;
-		video->ureq[i].req->complete = uvc_video_complete;
-		video->ureq[i].req->context = &video->ureq[i];
-		video->ureq[i].video = video;
-		video->ureq[i].last_buf = NULL;
-
-		list_add_tail(&video->ureq[i].req->list, &video->req_free);
+		ureq->req = usb_ep_alloc_request(video->ep, GFP_KERNEL);
+		if (ureq->req == NULL)
+			goto error;
+		ureq->req->buf = ureq->req_buffer;
+		ureq->req->length = 0;
+		ureq->req->complete = uvc_video_complete;
+		ureq->req->context = ureq;
+		ureq->video = video;
+		ureq->last_buf = NULL;
+		list_add_tail(&ureq->req->list, &video->req_free);
 		/* req_size/PAGE_SIZE + 1 for overruns and + 1 for header */
-		sg_alloc_table(&video->ureq[i].sgt,
+		sg_alloc_table(&ureq->sgt,
 			       DIV_ROUND_UP(req_size - UVCG_REQUEST_HEADER_LEN,
 					    PAGE_SIZE) + 2, GFP_KERNEL);
 	}
@@ -504,7 +510,7 @@ static void uvcg_video_pump(struct work_struct *work)
 int uvcg_video_enable(struct uvc_video *video, int enable)
 {
 	struct uvc_device *uvc = video->uvc;
-	unsigned int i;
+	struct uvc_request *ureq;
 	int ret;

 	if (video->ep == NULL) {
@@ -519,9 +525,10 @@ int uvcg_video_enable(struct uvc_video *video, int enable)
 		cancel_work_sync(&video->pump);
 		uvcg_queue_cancel(&video->queue, 0);

-		for (i = 0; i < video->uvc_num_requests; ++i)
-			if (video->ureq && video->ureq[i].req)
-				usb_ep_dequeue(video->ep, video->ureq[i].req);
+		list_for_each_entry(ureq, &video->ureqs, list) {
+			if (ureq->req)
+				usb_ep_dequeue(video->ep, ureq->req);
+		}

 		uvc_video_free_requests(video);
 		uvcg_queue_enable(&video->queue, 0);
@@ -555,6 +562,7 @@ int uvcg_video_enable(struct uvc_video *video, int enable)
  */
 int uvcg_video_init(struct uvc_video *video, struct uvc_device *uvc)
 {
+	INIT_LIST_HEAD(&video->ureqs);
 	INIT_LIST_HEAD(&video->req_free);
 	spin_lock_init(&video->req_lock);
 	INIT_WORK(&video->pump, uvcg_video_pump);
--
2.42.0.609.gbb76f46606-goog

On Thu, Oct 05, 2023 at 11:08:13AM -0700, Avichal Rakesh wrote:
>Currently, the uvc gadget driver allocates all uvc_requests as one array
>and deallocates them all when the video stream stops. This includes
>de-allocating all the usb_requests associated with those uvc_requests.
>This can lead to use-after-free issues if any of those de-allocated
>usb_requests were still owned by the usb controller.
>
>This patch is 1 of 2 patches addressing the use-after-free issue.
>Instead of bulk allocating all uvc_requests as an array, this patch
>allocates uvc_requests one at a time, which should allows for similar
>granularity when deallocating the uvc_requests. This patch has no
>functional changes other than allocating each uvc_request separately,
>and similarly freeing each of them separately.
>
>Link: https://lore.kernel.org/7cd81649-2795-45b6-8c10-b7df1055020d@google.com
>Suggested-by: Michael Grzeschik <mgr@pengutronix.de>

Please use my full address here. m.grzeschik@pengutronix.de

>Signed-off-by: Avichal Rakesh <arakesh@google.com>
>---
>v1 -> v2: Rebased to ToT
>V2 -> V3: Fix email threading goof-up
>
> drivers/usb/gadget/function/uvc.h       |  3 +-
> drivers/usb/gadget/function/uvc_video.c | 90 ++++++++++++++-----------
> 2 files changed, 51 insertions(+), 42 deletions(-)
>
>diff --git a/drivers/usb/gadget/function/uvc.h b/drivers/usb/gadget/function/uvc.h
>index 989bc6b4e93d..993694da0bbc 100644
>--- a/drivers/usb/gadget/function/uvc.h
>+++ b/drivers/usb/gadget/function/uvc.h
>@@ -81,6 +81,7 @@ struct uvc_request {
> 	struct sg_table sgt;
> 	u8 header[UVCG_REQUEST_HEADER_LEN];
> 	struct uvc_buffer *last_buf;
>+	struct list_head list;
> };
>
> struct uvc_video {
>@@ -102,7 +103,7 @@ struct uvc_video {
>
> 	/* Requests */
> 	unsigned int req_size;
>-	struct uvc_request *ureq;
>+	struct list_head ureqs; /* all uvc_requests allocated by uvc_video */
> 	struct list_head req_free;
> 	spinlock_t req_lock;
>
>diff --git a/drivers/usb/gadget/function/uvc_video.c b/drivers/usb/gadget/function/uvc_video.c
>index 97d875c27dcf..3c4d286d81c0 100644
>--- a/drivers/usb/gadget/function/uvc_video.c
>+++ b/drivers/usb/gadget/function/uvc_video.c
>@@ -227,6 +227,23 @@ uvc_video_encode_isoc(struct usb_request *req, struct uvc_video *video,
>  * Request handling
>  */
>
>+static void uvc_video_free_request(struct uvc_request *ureq, struct usb_ep *ep)
>+{
>+	sg_free_table(&ureq->sgt);
>+	if (ureq->req && ep) {
>+		usb_ep_free_request(ep, ureq->req);
>+		ureq->req = NULL;
>+	}
>+
>+	kfree(ureq->req_buffer);
>+	ureq->req_buffer = NULL;
>+
>+	if (!list_empty(&ureq->list))
>+		list_del_init(&ureq->list);
>+
>+	kfree(ureq);
>+}
>+
> static int uvcg_video_ep_queue(struct uvc_video *video, struct usb_request *req)
> {
> 	int ret;
>@@ -299,27 +316,13 @@ uvc_video_complete(struct usb_ep *ep, struct usb_request *req)
> static int
> uvc_video_free_requests(struct uvc_video *video)
> {
>-	unsigned int i;
>-
>-	if (video->ureq) {
>-		for (i = 0; i < video->uvc_num_requests; ++i) {
>-			sg_free_table(&video->ureq[i].sgt);
>-
>-			if (video->ureq[i].req) {
>-				usb_ep_free_request(video->ep, video->ureq[i].req);
>-				video->ureq[i].req = NULL;
>-			}
>+	struct uvc_request *ureq, *temp;
>
>-			if (video->ureq[i].req_buffer) {
>-				kfree(video->ureq[i].req_buffer);
>-				video->ureq[i].req_buffer = NULL;
>-			}
>-		}
>-
>-		kfree(video->ureq);
>-		video->ureq = NULL;
>+	list_for_each_entry_safe(ureq, temp, &video->ureqs, list) {
>+		uvc_video_free_request(ureq, video->ep);
> 	}

Please drop the extra braces.

>
>+	INIT_LIST_HEAD(&video->ureqs);
> 	INIT_LIST_HEAD(&video->req_free);
> 	video->req_size = 0;
> 	return 0;
>@@ -328,6 +331,7 @@ uvc_video_free_requests(struct uvc_video *video)
> static int
> uvc_video_alloc_requests(struct uvc_video *video)
> {
>+	struct uvc_request *ureq;
> 	unsigned int req_size;
> 	unsigned int i;
> 	int ret = -ENOMEM;
>@@ -338,29 +342,31 @@ uvc_video_alloc_requests(struct uvc_video *video)
> 		 * max_t(unsigned int, video->ep->maxburst, 1)
> 		 * (video->ep->mult);
>
>-	video->ureq = kcalloc(video->uvc_num_requests, sizeof(struct uvc_request), GFP_KERNEL);
>-	if (video->ureq == NULL)
>-		return -ENOMEM;
>-
>-	for (i = 0; i < video->uvc_num_requests; ++i) {
>-		video->ureq[i].req_buffer = kmalloc(req_size, GFP_KERNEL);
>-		if (video->ureq[i].req_buffer == NULL)
>+	INIT_LIST_HEAD(&video->ureqs);
>+	for (i = 0; i < video->uvc_num_requests; i++) {
>+		ureq = kzalloc(sizeof(struct uvc_request), GFP_KERNEL);
>+		if (ureq == NULL)
> 			goto error;
>+		INIT_LIST_HEAD(&ureq->list);
>+		list_add_tail(&ureq->list, &video->ureqs);
>+	}
>
>-		video->ureq[i].req = usb_ep_alloc_request(video->ep, GFP_KERNEL);
>-		if (video->ureq[i].req == NULL)
>+	list_for_each_entry(ureq, &video->ureqs, list) {
>+		ureq->req_buffer = kmalloc(req_size, GFP_KERNEL);
>+		if (ureq->req_buffer == NULL)
> 			goto error;
>-

Instead of looping twice. Wouldn't it be possible to fill the
just created ureq from the for loop here directly.

>-		video->ureq[i].req->buf = video->ureq[i].req_buffer;
>-		video->ureq[i].req->length = 0;
>-		video->ureq[i].req->complete = uvc_video_complete;
>-		video->ureq[i].req->context = &video->ureq[i];
>-		video->ureq[i].video = video;
>-		video->ureq[i].last_buf = NULL;
>-
>-		list_add_tail(&video->ureq[i].req->list, &video->req_free);
>+		ureq->req = usb_ep_alloc_request(video->ep, GFP_KERNEL);
>+		if (ureq->req == NULL)
>+			goto error;
>+		ureq->req->buf = ureq->req_buffer;
>+		ureq->req->length = 0;
>+		ureq->req->complete = uvc_video_complete;
>+		ureq->req->context = ureq;
>+		ureq->video = video;
>+		ureq->last_buf = NULL;

Add an extra spare line just like in the code before.

>+		list_add_tail(&ureq->req->list, &video->req_free);
> 		/* req_size/PAGE_SIZE + 1 for overruns and + 1 for header */
>-		sg_alloc_table(&video->ureq[i].sgt,
>+		sg_alloc_table(&ureq->sgt,
> 			       DIV_ROUND_UP(req_size - UVCG_REQUEST_HEADER_LEN,
> 					    PAGE_SIZE) + 2, GFP_KERNEL);
> 	}
>@@ -504,7 +510,7 @@ static void uvcg_video_pump(struct work_struct *work)
> int uvcg_video_enable(struct uvc_video *video, int enable)
> {
> 	struct uvc_device *uvc = video->uvc;
>-	unsigned int i;
>+	struct uvc_request *ureq;
> 	int ret;
>
> 	if (video->ep == NULL) {
>@@ -519,9 +525,10 @@ int uvcg_video_enable(struct uvc_video *video, int enable)
> 		cancel_work_sync(&video->pump);
> 		uvcg_queue_cancel(&video->queue, 0);
>
>-		for (i = 0; i < video->uvc_num_requests; ++i)
>-			if (video->ureq && video->ureq[i].req)
>-				usb_ep_dequeue(video->ep, video->ureq[i].req);
>+		list_for_each_entry(ureq, &video->ureqs, list) {
>+			if (ureq->req)
>+				usb_ep_dequeue(video->ep, ureq->req);
>+		}
>
> 		uvc_video_free_requests(video);
> 		uvcg_queue_enable(&video->queue, 0);
>@@ -555,6 +562,7 @@ int uvcg_video_enable(struct uvc_video *video, int enable)
>  */
> int uvcg_video_init(struct uvc_video *video, struct uvc_device *uvc)
> {
>+	INIT_LIST_HEAD(&video->ureqs);
> 	INIT_LIST_HEAD(&video->req_free);
> 	spin_lock_init(&video->req_lock);
> 	INIT_WORK(&video->pump, uvcg_video_pump);
>--
>2.42.0.609.gbb76f46606-goog
>

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

Currently, the uvc gadget driver allocates all uvc_requests as one array
and deallocates them all when the video stream stops. This includes
de-allocating all the usb_requests associated with those uvc_requests.
This can lead to use-after-free issues if any of those de-allocated
usb_requests were still owned by the usb controller.

This is patch 2 of 2 in fixing the use-after-free issue. It adds a new
flag to uvc_request to mark it as 'abandoned'. When disabling the video
stream, instead of de-allocating all uvc_requests and usb_requests, the
gadget driver only de-allocates those usb_requests that are currently
owned by the gadget driver (as present in req_free). Other usb_requests
have their corresponding 'is_abandoned' flag tripped, and the
usb_requests complete handler takes care of freeing the usb_request and
its corresponding uvc_request.

This should ensure that uvc gadget driver never accidentally de-allocates
a usb_request that it doesn't own.

Link: https://lore.kernel.org/7cd81649-2795-45b6-8c10-b7df1055020d@google.com
Suggested-by: Michael Grzeschik <mgr@pengutronix.de>
Signed-off-by: Avichal Rakesh <arakesh@google.com>
---
v1 -> v2: Rebased to ToT, and fixed deadlock reported in
          https://lore.kernel.org/all/ZRv2UnKztgyqk2pt@pengutronix.de/
v2 -> v3: Fix email threading goof-up

 drivers/usb/gadget/function/uvc.h       |   1 +
 drivers/usb/gadget/function/uvc_video.c | 118 ++++++++++++++++++++----
 2 files changed, 102 insertions(+), 17 deletions(-)

diff --git a/drivers/usb/gadget/function/uvc.h b/drivers/usb/gadget/function/uvc.h
index 993694da0bbc..e69cfb7cced1 100644
--- a/drivers/usb/gadget/function/uvc.h
+++ b/drivers/usb/gadget/function/uvc.h
@@ -82,6 +82,7 @@ struct uvc_request {
 	u8 header[UVCG_REQUEST_HEADER_LEN];
 	struct uvc_buffer *last_buf;
 	struct list_head list;
+	bool is_abandoned;
 };

 struct uvc_video {
diff --git a/drivers/usb/gadget/function/uvc_video.c b/drivers/usb/gadget/function/uvc_video.c
index 3c4d286d81c0..69521886d599 100644
--- a/drivers/usb/gadget/function/uvc_video.c
+++ b/drivers/usb/gadget/function/uvc_video.c
@@ -271,7 +271,21 @@ uvc_video_complete(struct usb_ep *ep, struct usb_request *req)
 	struct uvc_video *video = ureq->video;
 	struct uvc_video_queue *queue = &video->queue;
 	struct uvc_device *uvc = video->uvc;
+	struct uvc_buffer *last_buf;
 	unsigned long flags;
+	bool is_abandoned;
+
+	spin_lock_irqsave(&video->req_lock, flags);
+	is_abandoned = ureq->is_abandoned;
+	last_buf = ureq->last_buf;
+	ureq->last_buf = NULL;
+	spin_unlock_irqrestore(&video->req_lock, flags);
+
+	if (is_abandoned) {
+		uvcg_dbg(&video->uvc->func, "Freeing abandoned usb_request\n");
+		uvc_video_free_request(ureq, ep);
+		return;
+	}

 	if (uvc->state == UVC_STATE_CONNECTED) {
 		usb_ep_free_request(video->ep, ureq->req);
@@ -300,15 +314,29 @@ uvc_video_complete(struct usb_ep *ep, struct usb_request *req)
 		uvcg_queue_cancel(queue, 0);
 	}

-	if (ureq->last_buf) {
-		uvcg_complete_buffer(&video->queue, ureq->last_buf);
-		ureq->last_buf = NULL;
+	if (last_buf) {
+		spin_lock_irqsave(&video->queue.irqlock, flags);
+		uvcg_complete_buffer(&video->queue, last_buf);
+		spin_unlock_irqrestore(&video->queue.irqlock, flags);
 	}

+	/*
+	 * request might have been abandoned while being processed.
+	 * do a last minute check before queueing the request back.
+	 */
 	spin_lock_irqsave(&video->req_lock, flags);
-	list_add_tail(&req->list, &video->req_free);
+	is_abandoned = ureq->is_abandoned;
+	if (!is_abandoned)
+		list_add_tail(&req->list, &video->req_free);
 	spin_unlock_irqrestore(&video->req_lock, flags);

+	if (is_abandoned) {
+		uvcg_dbg(&video->uvc->func,
+			 "usb_request abandoned mid-processing - freeing.\n");
+		uvc_video_free_request(ureq, ep);
+		return;
+	}
+
 	if (uvc->state == UVC_STATE_STREAMING)
 		queue_work(video->async_wq, &video->pump);
 }
@@ -372,7 +400,6 @@ uvc_video_alloc_requests(struct uvc_video *video)
 	}

 	video->req_size = req_size;
-
 	return 0;

 error:
@@ -504,13 +531,80 @@ static void uvcg_video_pump(struct work_struct *work)
 	return;
 }

+/*
+ * Disable video stream. This ensures that any inflight usb requests are marked
+ * for clean up and all video buffers are dropped before returning.
+ */
+static void uvcg_video_disable(struct uvc_video *video)
+{
+	struct uvc_buffer *buf, *tmp_buf;
+	struct uvc_request *ureq, *temp;
+	struct list_head buf_list; /* track in-flight video buffers */
+	struct usb_request *req;
+	unsigned long flags;
+
+	INIT_LIST_HEAD(&buf_list);
+
+	cancel_work_sync(&video->pump);
+	uvcg_queue_cancel(&video->queue, 0);
+
+	list_for_each_entry(ureq, &video->ureqs, list) {
+		if (ureq->req)
+			usb_ep_dequeue(video->ep, ureq->req);
+	}
+
+	/**
+	 * acquiring req_lock here should prevent any more complete
+	 * callbacks from processing until we've abandoned the
+	 * requests that are still in-flight and let the complete
+	 * callback handle cleanup
+	 */
+	spin_lock_irqsave(&video->req_lock, flags);
+	/* abandon all usb requests */
+	list_for_each_entry_safe(ureq, temp, &video->ureqs, list) {
+		ureq->is_abandoned = true;
+		if (ureq->last_buf) {
+			list_add(&ureq->last_buf->queue, &buf_list);
+			ureq->last_buf = NULL;
+		}
+		list_del_init(&ureq->list);
+	}
+	/*
+	 * re-add uvc_requests currently owned by the gadget to
+	 * video->ureqs to be deallocated. This effectively leaves
+	 * video->ureqs with the requests that we currently own.
+	 */
+	list_for_each_entry(req, &video->req_free, list) {
+		ureq = req->context;
+		list_add_tail(&ureq->list, &video->ureqs);
+	}
+	spin_unlock_irqrestore(&video->req_lock, flags);
+
+	/*
+	 * drop abandoned uvc_buffers, as the completion handler
+	 * no longer will
+	 */
+	if (!list_empty(&buf_list)) {
+		spin_lock_irqsave(&video->queue.irqlock, flags);
+		list_for_each_entry_safe(buf, tmp_buf,
+						&buf_list, queue) {
+			video->queue.flags |= UVC_QUEUE_DROP_INCOMPLETE;
+			uvcg_complete_buffer(&video->queue, buf);
+			list_del(&buf->queue);
+		}
+		spin_unlock_irqrestore(&video->queue.irqlock, flags);
+	}
+
+	uvc_video_free_requests(video);
+	uvcg_queue_enable(&video->queue, 0);
+}
+
 /*
  * Enable or disable the video stream.
  */
 int uvcg_video_enable(struct uvc_video *video, int enable)
 {
 	struct uvc_device *uvc = video->uvc;
-	struct uvc_request *ureq;
 	int ret;

 	if (video->ep == NULL) {
@@ -521,17 +615,7 @@ int uvcg_video_enable(struct uvc_video *video, int enable)

 	if (!enable) {
 		uvc->state = UVC_STATE_CONNECTED;
-
-		cancel_work_sync(&video->pump);
-		uvcg_queue_cancel(&video->queue, 0);
-
-		list_for_each_entry(ureq, &video->ureqs, list) {
-			if (ureq->req)
-				usb_ep_dequeue(video->ep, ureq->req);
-		}
-
-		uvc_video_free_requests(video);
-		uvcg_queue_enable(&video->queue, 0);
+		uvcg_video_disable(video);
 		return 0;
 	}

--
2.42.0.609.gbb76f46606-goog