On 10/18/23 06:10, Michael Grzeschik wrote:
On Wed, Oct 11, 2023 at 05:24:51PM -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 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 accomodate 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@xxxxxxxxxx
Suggested-by: Michael Grzeschik <m.grzeschik@xxxxxxxxxxxxxx>
Signed-off-by: Avichal Rakesh <arakesh@xxxxxxxxxx>
---
v1 -> v2: Rebased to ToT, and fixed deadlock reported in
https://lore.kernel.org/all/ZRv2UnKztgyqk2pt@xxxxxxxxxxxxxx/
v2 -> v3: Fix email threading goof-up
v3 -> v4: re-rebase to ToT & moved to a uvc_video level lock
as discussed in
https://lore.kernel.org/b14b296f-2e08-4edf-aeea-1c5b621e2d0c@xxxxxxxxxx/
I tested this and I no longer saw any use after free
errors anymore! :)
Yay! Glad to hear!
Here comes some more review:
drivers/usb/gadget/function/uvc.h | 1 +
drivers/usb/gadget/function/uvc_v4l2.c | 12 +-
drivers/usb/gadget/function/uvc_video.c | 156 +++++++++++++++++++-----
3 files changed, 128 insertions(+), 41 deletions(-)
+
+/*
+ * Disable video stream
+ */
+static int
+uvcg_video_disable(struct uvc_video *video) {
+ unsigned long flags;
+ struct list_head inflight_bufs;
+ struct usb_request *req, *temp;
+ struct uvc_buffer *buf, *btemp;
+ struct uvc_request *ureq, *utemp;
+
+ 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);
- return;
+
+ cancel_work_sync(&video->pump);
+ uvcg_queue_cancel(&video->queue, 0);
+
+ spin_lock_irqsave(&video->req_lock, flags);
+ /*
+ * Remove all uvc_reqeusts from 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);
+ }
+
+ 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;
}
/*
@@ -497,28 +596,22 @@ static void uvcg_video_pump(struct work_struct *work)
int uvcg_video_enable(struct uvc_video *video, int enable)
{
int ret;
- struct uvc_request *ureq;
if (video->ep == NULL) {
uvcg_info(&video->uvc->func,
"Video enable failed, device is uninitialized.\n");
return -ENODEV;
}
-
- if (!enable) {
- 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);
- return 0;
- }
-
+ if (!enable)
+ return uvcg_video_disable(video);
Could you refactor this code as it is to an separate
function and prepand this change as an extra patch
to this one? It would make the changes in the functions
more obvious and better to review.
Sure I can send a follow up patch, but I am curious why you think this
needs to be a separate function? Refactoring into a function would
have the functions structured something like:
uvcg_video_disable(video) {
// ...
// disable impl
// ...
}
uvcg_video_enable(video) {
// ...
// enable impl
// ...
}
uvcg_video_enable(video, enable) {
// ep test
if (!enable)
return uvcg_video_disable(video);
return uvc_video_enable(video);
}
instead of the current structure:
uvcg_video_disable(video) {
// ...
// disable impl
// ...
}
uvcg_video_enable(video, enable) {
// ep test
if (!enable)
return uvcg_video_disable(video);
// ...
// enable impl
// ...
}
I am not sure if one is more readable than the other.
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