From 7de8681be2cde9f6953d3be1fa6ce05f9fe6e637 Mon Sep 17 00:00:00 2001
From: Jack Pham <jackp@codeaurora.org>
Date: Mon, 18 Jan 2021 09:46:39 +0100
Subject: [PATCH] usb: gadget: u_audio: Free requests only after callback
Git-commit: 7de8681be2cde9f6953d3be1fa6ce05f9fe6e637
Patch-mainline: v5.12-rc1
References: git-fixes

As per the kernel doc for usb_ep_dequeue(), it states that "this
routine is asynchronous, that is, it may return before the completion
routine runs". And indeed since v5.0 the dwc3 gadget driver updated
its behavior to place dequeued requests on to a cancelled list to be
given back later after the endpoint is stopped.

The free_ep() was incorrectly assuming that a request was ready to
be freed after calling dequeue which results in a use-after-free
in dwc3 when it traverses its cancelled list. Fix this by moving
the usb_ep_free_request() call to the callback itself in case the
ep is disabled.

Fixes: eb9fecb9e69b0 ("usb: gadget: f_uac2: split out audio core")
Reported-and-tested-by: Ferry Toth <fntoth@gmail.com>
Reviewed-and-tested-by: Peter Chen <peter.chen@nxp.com>
Acked-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Jack Pham <jackp@codeaurora.org>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Link: https://lore.kernel.org/r/20210118084642.322510-2-jbrunet@baylibre.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/usb/gadget/function/u_audio.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/gadget/function/u_audio.c b/drivers/usb/gadget/function/u_audio.c
index e6d32c536781..908e49dafd62 100644
--- a/drivers/usb/gadget/function/u_audio.c
+++ b/drivers/usb/gadget/function/u_audio.c
@@ -89,7 +89,12 @@ static void u_audio_iso_complete(struct usb_ep *ep, struct usb_request *req)
 	struct snd_uac_chip *uac = prm->uac;
 
 	/* i/f shutting down */
-	if (!prm->ep_enabled || req->status == -ESHUTDOWN)
+	if (!prm->ep_enabled) {
+		usb_ep_free_request(ep, req);
+		return;
+	}
+
+	if (req->status == -ESHUTDOWN)
 		return;
 
 	/*
@@ -336,8 +341,14 @@ static inline void free_ep(struct uac_rtd_params *prm, struct usb_ep *ep)
 
 	for (i = 0; i < params->req_number; i++) {
 		if (prm->ureq[i].req) {
-			usb_ep_dequeue(ep, prm->ureq[i].req);
-			usb_ep_free_request(ep, prm->ureq[i].req);
+			if (usb_ep_dequeue(ep, prm->ureq[i].req))
+				usb_ep_free_request(ep, prm->ureq[i].req);
+			/*
+			 * If usb_ep_dequeue() cannot successfully dequeue the
+			 * request, the request will be freed by the completion
+			 * callback.
+			 */
+
 			prm->ureq[i].req = NULL;
 		}
 	}
-- 
2.26.2