linux-kernel - [PATCH] usb: gadget: uvc: fix list double add in uvcg_video

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Date:   Wed, 15 Jun 2022 22:09:15 -0500
From:   Dan Vacura <w36195@...orola.com>
To:     linux-usb@...r.kernel.org
Cc:     Dan Vacura <w36195@...orola.com>, stable@...r.kernel.org,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Paul Elder <paul.elder@...asonboard.com>,
        Michael Grzeschik <m.grzeschik@...gutronix.de>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] usb: gadget: uvc: fix list double add in uvcg_video_pump

A panic can occur if the endpoint becomes disabled and the
uvcg_video_pump adds the request back to the req_free list after it has
already been queued to the endpoint. The endpoint complete will add the
request back to the req_free list. Invalidate the local request handle
once it's been queued.

<6>[  246.796704][T13726] configfs-gadget gadget: uvc: uvc_function_set_alt(1, 0)
<3>[  246.797078][   T26] list_add double add: new=ffffff878bee5c40, prev=ffffff878bee5c40, next=ffffff878b0f0a90.
<6>[  246.797213][   T26] ------------[ cut here ]------------
<2>[  246.797224][   T26] kernel BUG at lib/list_debug.c:31!
<6>[  246.807073][   T26] Call trace:
<6>[  246.807180][   T26]  uvcg_video_pump+0x364/0x38c
<6>[  246.807366][   T26]  process_one_work+0x2a4/0x544
<6>[  246.807394][   T26]  worker_thread+0x350/0x784
<6>[  246.807442][   T26]  kthread+0x2ac/0x320

Fixes: f9897ec0f6d3 ("usb: gadget: uvc: only pump video data if necessary")
Cc: stable@...r.kernel.org
Signed-off-by: Dan Vacura <w36195@...orola.com>
---
 drivers/usb/gadget/function/uvc_video.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/usb/gadget/function/uvc_video.c b/drivers/usb/gadget/function/uvc_video.c
index 93f42c7f800d..59e2f51b53a5 100644
--- a/drivers/usb/gadget/function/uvc_video.c
+++ b/drivers/usb/gadget/function/uvc_video.c
@@ -427,6 +427,9 @@ static void uvcg_video_pump(struct work_struct *work)
 		if (ret < 0) {
 			uvcg_queue_cancel(queue, 0);
 			break;
+		} else {
+			/* Endpoint now owns the request */
+			req = NULL;
 		}
 		video->req_int_count++;
 	}
-- 
2.34.1