[PATCH v2] usb: dwc3: gadget: Fix use-after-free in dwc3_gadget_free_endpoints due to race condition

[PATCH v2] usb: dwc3: gadget: Fix use-after-free in dwc3_gadget_free_endpoints due to race condition

[Pei Xiao]

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
Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Cc: stable@vger.kernel.org
Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
---
changes in v2:
add Acked-by add Cc stable
---
 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

Re: [PATCH v2] usb: dwc3: gadget: Fix use-after-free in dwc3_gadget_free_endpoints due to race condition

[Pandey, Radhey Shyam]

On 8/5/2026 7:10 AM, Pei Xiao wrote:
> 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
> Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
> Cc: stable@vger.kernel.org
> Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>

Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@amd.com>
Thanks!> ---
> changes in v2:
> add Acked-by add Cc stable
> ---
>   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);
>   	}
>   }