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Code Issues Releases Wiki Activity

usb: gadget: uvc: Fix use-after-free for inflight usb_requests

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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_video to track when frames and requests should be flowing.
When disabling the video stream, the flag is tripped and, instead
of de-allocating all uvc_requests and usb_requests, the gadget
driver only de-allocates those usb_requests that are currently
owned by it (as present in req_free). Other usb_requests are left
untouched until their completion handler is called which takes care
of freeing the usb_request and its corresponding uvc_request.

Now that uvc_video does not depends on uvc->state, this patch removes
unnecessary upates to uvc->state that were made to accommodate uvc_video
logic. 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
Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>
Reviewed-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Suggested-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Tested-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: Avichal Rakesh <arakesh@google.com>
Link: https://lore.kernel.org/r/20231109004104.3467968-4-arakesh@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Avichal Rakesh 2023-11-08 16:41:04 -08:00 committed by Greg Kroah-Hartman
parent 2079b60bda
commit da324ffce3
3 changed files with 112 additions and 29 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

1
drivers/usb/gadget/function/uvc.h
View file

@ -102,6 +102,7 @@ struct uvc_video {
unsigned int uvc_num_requests;
/* Requests */
bool is_enabled; /* tracks whether video stream is enabled */
unsigned int req_size;
struct list_head ureqs; /* all uvc_requests allocated by uvc_video */
struct list_head req_free;

10
drivers/usb/gadget/function/uvc_v4l2.c
View file

@ -468,11 +468,11 @@ uvc_v4l2_streamoff(struct file *file, void *fh, enum v4l2_buf_type type)
if (type != video->queue.queue.type)
return -EINVAL;
uvc->state = UVC_STATE_CONNECTED;
ret = uvcg_video_disable(video);
if (ret < 0)
return ret;
uvc->state = UVC_STATE_CONNECTED;
uvc_function_setup_continue(uvc, 1);
return 0;
}
@ -507,14 +507,6 @@ uvc_v4l2_subscribe_event(struct v4l2_fh *fh,
static void uvc_v4l2_disable(struct uvc_device *uvc)
{
uvc_function_disconnect(uvc);
/*
* Drop uvc->state to CONNECTED if it was streaming before.
* This ensures that the usb_requests are no longer queued
* to the controller.
*/
if (uvc->state == UVC_STATE_STREAMING)
uvc->state = UVC_STATE_CONNECTED;
uvcg_video_disable(&uvc->video);
uvcg_free_buffers(&uvc->video.queue);
uvc->func_connected = false;

126
drivers/usb/gadget/function/uvc_video.c
View file

@ -227,6 +227,10 @@ uvc_video_encode_isoc(struct usb_request *req, struct uvc_video *video,
* Request handling
*/
/*
* Callers must take care to hold req_lock when this function may be called
* from multiple threads. For example, when frames are streaming to the host.
*/
static void
uvc_video_free_request(struct uvc_request *ureq, struct usb_ep *ep)
{
@ -271,9 +275,26 @@ uvc_video_complete(struct usb_ep *ep, struct usb_request *req)
struct uvc_request *ureq = req->context;
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;
spin_lock_irqsave(&video->req_lock, flags);
if (!video->is_enabled) {
/*
* When is_enabled is false, uvcg_video_disable() ensures
* that in-flight uvc_buffers are returned, so we can
* safely call free_request without worrying about
* last_buf.
*/
uvc_video_free_request(ureq, ep);
spin_unlock_irqrestore(&video->req_lock, flags);
return;
}
last_buf = ureq->last_buf;
ureq->last_buf = NULL;
spin_unlock_irqrestore(&video->req_lock, flags);
switch (req->status) {
case 0:
break;
@ -295,17 +316,26 @@ 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(&queue->irqlock, flags);
uvcg_complete_buffer(queue, last_buf);
spin_unlock_irqrestore(&queue->irqlock, flags);
}
spin_lock_irqsave(&video->req_lock, flags);
/*
* Video stream might have been disabled while we were
* processing the current usb_request. So make sure
* we're still streaming before queueing the usb_request
* back to req_free
*/
if (video->is_enabled) {
list_add_tail(&req->list, &video->req_free);
spin_unlock_irqrestore(&video->req_lock, flags);
if (uvc->state == UVC_STATE_STREAMING)
queue_work(video->async_wq, &video->pump);
} else {
uvc_video_free_request(ureq, ep);
}
spin_unlock_irqrestore(&video->req_lock, flags);
}
static int
@ -392,20 +422,22 @@ static void uvcg_video_pump(struct work_struct *work)
struct uvc_video_queue *queue = &video->queue;
/* video->max_payload_size is only set when using bulk transfer */
bool is_bulk = video->max_payload_size;
struct uvc_device *uvc = video->uvc;
struct usb_request *req = NULL;
struct uvc_buffer *buf;
unsigned long flags;
bool buf_done;
int ret;
while (uvc->state == UVC_STATE_STREAMING && video->ep->enabled) {
while (true) {
if (!video->ep->enabled)
return;
/*
* Retrieve the first available USB request, protected by the
* request lock.
* Check is_enabled and retrieve the first available USB
* request, protected by the request lock.
*/
spin_lock_irqsave(&video->req_lock, flags);
if (list_empty(&video->req_free)) {
if (!video->is_enabled || list_empty(&video->req_free)) {
spin_unlock_irqrestore(&video->req_lock, flags);
return;
}
@ -487,9 +519,11 @@ static void uvcg_video_pump(struct work_struct *work)
return;
spin_lock_irqsave(&video->req_lock, flags);
if (video->is_enabled)
list_add_tail(&req->list, &video->req_free);
else
uvc_video_free_request(req->context, video->ep);
spin_unlock_irqrestore(&video->req_lock, flags);
return;
}
/*
@ -498,7 +532,11 @@ static void uvcg_video_pump(struct work_struct *work)
int
uvcg_video_disable(struct uvc_video *video)
{
struct uvc_request *ureq;
unsigned long flags;
struct list_head inflight_bufs;
struct usb_request *req, *temp;
struct uvc_buffer *buf, *btemp;
struct uvc_request *ureq, *utemp;
if (video->ep == NULL) {
uvcg_info(&video->uvc->func,
@ -506,15 +544,58 @@ uvcg_video_disable(struct uvc_video *video)
return -ENODEV;
}
INIT_LIST_HEAD(&inflight_bufs);
spin_lock_irqsave(&video->req_lock, flags);
video->is_enabled = false;
/*
* Remove any in-flight buffers from the uvc_requests
* because we want to return them before cancelling the
* queue. This ensures that we aren't stuck waiting for
* all complete callbacks to come through before disabling
* vb2 queue.
*/
list_for_each_entry(ureq, &video->ureqs, list) {
if (ureq->last_buf) {
list_add_tail(&ureq->last_buf->queue, &inflight_bufs);
ureq->last_buf = NULL;
}
}
spin_unlock_irqrestore(&video->req_lock, flags);
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);
spin_lock_irqsave(&video->req_lock, flags);
/*
* Remove all uvc_requests from ureqs with list_del_init
* This lets uvc_video_free_request correctly identify
* if the uvc_request is attached to a list or not when freeing
* memory.
*/
list_for_each_entry_safe(ureq, utemp, &video->ureqs, list)
list_del_init(&ureq->list);
list_for_each_entry_safe(req, temp, &video->req_free, list) {
list_del(&req->list);
uvc_video_free_request(req->context, video->ep);
}
uvc_video_free_requests(video);
INIT_LIST_HEAD(&video->ureqs);
INIT_LIST_HEAD(&video->req_free);
video->req_size = 0;
spin_unlock_irqrestore(&video->req_lock, flags);
/*
* Return all the video buffers before disabling the queue.
*/
spin_lock_irqsave(&video->queue.irqlock, flags);
list_for_each_entry_safe(buf, btemp, &inflight_bufs, queue) {
list_del(&buf->queue);
uvcg_complete_buffer(&video->queue, buf);
}
spin_unlock_irqrestore(&video->queue.irqlock, flags);
uvcg_queue_enable(&video->queue, 0);
return 0;
}
@ -532,6 +613,14 @@ int uvcg_video_enable(struct uvc_video *video)
return -ENODEV;
}
/*
* Safe to access request related fields without req_lock because
* this is the only thread currently active, and no other
* request handling thread will become active until this function
* returns.
*/
video->is_enabled = true;
if ((ret = uvcg_queue_enable(&video->queue, 1)) < 0)
return ret;
@ -557,6 +646,7 @@ int uvcg_video_enable(struct uvc_video *video)
*/
int uvcg_video_init(struct uvc_video *video, struct uvc_device *uvc)
{
video->is_enabled = false;
INIT_LIST_HEAD(&video->ureqs);
INIT_LIST_HEAD(&video->req_free);
spin_lock_init(&video->req_lock);