usb: gadget: uvc: Fix use are free during STREAMOFF

There is a path that may lead to freed memory being referenced,
causing kernel panics.

The kernel panic has the following stack trace:

Workqueue: uvcgadget uvcg_video_pump.c51fb85fece46625450f86adbf92c56c.cfi_jt
pstate: 60c00085 (nZCv daIf +PAN +UAO -TCO BTYPE=--)
pc : __list_del_entry_valid+0xc0/0xd4
lr : __list_del_entry_valid+0xc0/0xd4
Call trace:
  __list_del_entry_valid+0xc0/0xd4
  uvc_video_free_request+0x60/0x98
  uvcg_video_pump+0x1cc/0x204
  process_one_work+0x21c/0x4b8
  worker_thread+0x29c/0x574
  kthread+0x158/0x1b0
  ret_from_fork+0x10/0x30

The root cause is that uvcg_video_usb_req_queue frees the uvc_request
if is_enabled is false and returns an error status. video_pump also
frees the associated request if uvcg_video_usb_req_queue returns an
error status, leading to double free and accessing garbage memory.

To fix the issue, this patch removes freeing logic from
uvcg_video_usb_req_queue, and lets the callers to the function handle
queueing errors as they see fit.

Fixes: 6acba0345b68 ("usb:gadget:uvc Do not use worker thread to pump isoc usb requests")
Tested-by: Avichal Rakesh <arakesh@google.com>
Signed-off-by: Avichal Rakesh <arakesh@google.com>
Link: https://lore.kernel.org/r/20240104215009.2252452-1-arakesh@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/gadget/function/uvc_video.c b/drivers/usb/gadget/function/uvc_video.c
index 98ba524c27f50a443a973a655b92ec0c39cf6948..7f18dc471be38faf811063622b1a0b4d6a5b2104 100644 (file)
--- a/drivers/usb/gadget/function/uvc_video.c
+++ b/drivers/usb/gadget/function/uvc_video.c
@@ -276,10 +276,9 @@ static int uvcg_video_usb_req_queue(struct uvc_video *video,
        bool is_bulk = video->max_payload_size;
        struct list_head *list = NULL;
 
-       if (!video->is_enabled) {
-               uvc_video_free_request(req->context, video->ep);
+       if (!video->is_enabled)
                return -ENODEV;
-       }
+
        if (queue_to_ep) {
                struct uvc_request *ureq = req->context;
                /*
@@ -464,8 +463,15 @@ uvc_video_complete(struct usb_ep *ep, struct usb_request *req)
                 * and this thread for isoc endpoints.
                 */
                ret = uvcg_video_usb_req_queue(video, to_queue, !is_bulk);
-               if (ret < 0)
+               if (ret < 0) {
+                       /*
+                        * Endpoint error, but the stream is still enabled.
+                        * Put request back in req_free for it to be cleaned
+                        * up later.
+                        */
                        uvcg_queue_cancel(queue, 0);
+                       list_add_tail(&to_queue->list, &video->req_free);
+               }
        } else {
                uvc_video_free_request(ureq, ep);
        }