[PATCH] usb: dwc3: gadget: Fix use-after-free in dwc3_gadget_free_endpoints due to race condition

In dwc3_gadget_init_endpoint, &dep->nostream_work is bound with
dwc3_nostream_work, and dwc3_gadget_endpoint_stream_event can queue
this delayed work on system_percpu_wq when a DEPEVT_STREAM_NOSTREAM
event is received.

If we remove the gadget, dwc3_gadget_free_endpoints makes cleanup and
the memory allocated for dep with kzalloc() is released by kfree(dep),
while the delayed work mentioned above may still be pending or
running. The sequence of operations that may lead to a UAF bug is as
follows:

CPU0                                      CPU1

                                          | dwc3_thread_interrupt
                                          | dwc3_endpoint_interrupt
                                          | dwc3_gadget_endpoint_stream_event
                                          | queue_delayed_work(system_percpu_wq,
                                          |                    &dep->nostream_work)
dwc3_gadget_free_endpoints                |
dwc3_free_trb_pool(dep)                   |
list_del(&dep->endpoint.ep_list)          |
dwc3_debugfs_remove_endpoint_dir(dep)     |
kfree(dep)                                |
// dep is freed                           |
                                          | dwc3_nostream_work
                                          | // use dep (use-after-free)

Fix it by canceling the delayed work before kfree(dep) in
dwc3_gadget_free_endpoints.

Fixes: dcfe437492e2 ("usb: dwc3: gadget: Reinitiate stream for all host NoStream behavior")
Assisted-by: Codex:deepseek-v4-flash
Signed-off-by: Pei Xiao <[email protected]>
---
 drivers/usb/dwc3/gadget.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index fa0f16ffafef..fa944856f956 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -3508,6 +3508,7 @@ static void dwc3_gadget_free_endpoints(struct dwc3 *dwc)
 		}
 
 		dwc3_debugfs_remove_endpoint_dir(dep);
+		cancel_delayed_work_sync(&dep->nostream_work);
 		kfree(dep);
 	}
 }
-- 
2.25.1