[PATCH v2] usb: dwc3: gadget: free trb pool only from epnum 2

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From: George Cherian <george.cherian@xxxxxx>

we never allocate a TRB pool for physical endpoints
0 and 1 so trying to free it (a invalid TRB pool pointer)
will lead us in a warning while removing dwc3.ko module.

In order to fix the situation, all we have to do is skip
dwc3_free_trb_pool() for physical endpoints 0 and 1 just
as we while deleting endpoints from the endpoints list.

Cc: stable@xxxxxxxxxxxxxxx # v3.2+
Signed-off-by: George Cherian <george.cherian@xxxxxx>
Signed-off-by: Felipe Balbi <balbi@xxxxxx>
---

Improved the comment in the driver a little bit.

Also, Ccing stable. This should be backported as far back
as possible. This bug exists since first version of the
driver back in v3.2.

 drivers/usb/dwc3/gadget.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 2b6e7e0..b5e5b35 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1706,11 +1706,19 @@ static void dwc3_gadget_free_endpoints(struct dwc3 *dwc)
 		dep = dwc->eps[epnum];
 		if (!dep)
 			continue;
-
-		dwc3_free_trb_pool(dep);
-
-		if (epnum != 0 && epnum != 1)
+		/*
+		 * Physical endpoints 0 and 1 are special; they form the
+		 * bi-directional USB endpoint 0.
+		 *
+		 * For those two physical endpoints, we don't allocate a TRB
+		 * pool nor do we add them the endpoints list. Due to that, we
+		 * shouldn't do these two operations otherwise we would end up
+		 * with all sorts of bugs when removing dwc3.ko.
+		 */
+		if (epnum != 0 && epnum != 1) {
+			dwc3_free_trb_pool(dep);
 			list_del(&dep->endpoint.ep_list);
+		}
 
 		kfree(dep);
 	}
-- 
1.8.2.1

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