[PATCH] usb: gadget: u_audio: fix race condition on endpoint stop

From: Jerome Brunet
Date: Fri Aug 27 2021 - 05:30:01 EST


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")
Reported-by: Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx>
Signed-off-by: Jerome Brunet <jbrunet@xxxxxxxxxxxx>
---
drivers/usb/gadget/function/u_audio.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/gadget/function/u_audio.c b/drivers/usb/gadget/function/u_audio.c
index 63d9340f008e..9e5c950612d0 100644
--- a/drivers/usb/gadget/function/u_audio.c
+++ b/drivers/usb/gadget/function/u_audio.c
@@ -394,8 +394,6 @@ 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;

@@ -413,6 +411,8 @@ 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__);
}
@@ -424,8 +424,6 @@ static inline void free_ep_fback(struct uac_rtd_params *prm, struct usb_ep *ep)
if (!prm->fb_ep_enabled)
return;

- prm->fb_ep_enabled = false;
-
if (prm->req_fback) {
if (usb_ep_dequeue(ep, prm->req_fback)) {
kfree(prm->req_fback->buf);
@@ -434,6 +432,8 @@ static inline void free_ep_fback(struct uac_rtd_params *prm, struct usb_ep *ep)
prm->req_fback = NULL;
}

+ prm->fb_ep_enabled = false;
+
if (usb_ep_disable(ep))
dev_err(uac->card->dev, "%s:%d Error!\n", __func__, __LINE__);
}
--
2.33.0