linux-kernel - [PATCH 4.19 19/33] usb: gadget: u_audio: fix race condition on endpoint stop

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Message-Id: <20210901122251.421638380@linuxfoundation.org>
Date:   Wed,  1 Sep 2021 14:28:08 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 19/33] usb: gadget: u_audio: fix race condition on endpoint stop

From: Jerome Brunet <jbrunet@...libre.com>

[ Upstream commit 068fdad20454f815e61e6f6eb9f051a8b3120e88 ]

If the endpoint completion callback is call right after the ep_enabled flag
is cleared and before usb_ep_dequeue() is call, we could do a double free
on the request and the associated buffer.

Fix this by clearing ep_enabled after all the endpoint requests have been
dequeued.

Fixes: 7de8681be2cd ("usb: gadget: u_audio: Free requests only after callback")
Cc: stable <stable@...r.kernel.org>
Reported-by: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
Link: https://lore.kernel.org/r/20210827092927.366482-1-jbrunet@baylibre.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/usb/gadget/function/u_audio.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/gadget/function/u_audio.c b/drivers/usb/gadget/function/u_audio.c
index 0cb0c638fd13..168303f21bf4 100644
--- a/drivers/usb/gadget/function/u_audio.c
+++ b/drivers/usb/gadget/function/u_audio.c
@@ -349,8 +349,6 @@ static inline void free_ep(struct uac_rtd_params *prm, struct usb_ep *ep)
 	if (!prm->ep_enabled)
 		return;
 
-	prm->ep_enabled = false;
-
 	audio_dev = uac->audio_dev;
 	params = &audio_dev->params;
 
@@ -368,11 +366,12 @@ static inline void free_ep(struct uac_rtd_params *prm, struct usb_ep *ep)
 		}
 	}
 
+	prm->ep_enabled = false;
+
 	if (usb_ep_disable(ep))
 		dev_err(uac->card->dev, "%s:%d Error!\n", __func__, __LINE__);
 }
 
-
 int u_audio_start_capture(struct g_audio *audio_dev)
 {
 	struct snd_uac_chip *uac = audio_dev->uac;
-- 
2.30.2