patch "usb: gadget: f_ecm: Use atomic_t to track in-flight request" added to usb-testing

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    usb: gadget: f_ecm: Use atomic_t to track in-flight request

to my usb git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-testing branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will be merged to the usb-next branch sometime soon,
after it passes testing, and the merge window is open.

If you have any questions about this process, please let me know.


From d710562e01c48d59be3f60d58b7a85958b39aeda Mon Sep 17 00:00:00 2001
From: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Date: Thu, 9 Jan 2020 13:17:22 +0000
Subject: usb: gadget: f_ecm: Use atomic_t to track in-flight request

Currently ecm->notify_req is used to flag when a request is in-flight.
ecm->notify_req is set to NULL and when a request completes it is
subsequently reset.

This is fundamentally buggy in that the unbind logic of the ECM driver will
unconditionally free ecm->notify_req leading to a NULL pointer dereference.

Fixes: da741b8c56d6 ("usb ethernet gadget: split CDC Ethernet function")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/usb/gadget/function/f_ecm.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/gadget/function/f_ecm.c b/drivers/usb/gadget/function/f_ecm.c
index 460d5d7c984f..7f5cf488b2b1 100644
--- a/drivers/usb/gadget/function/f_ecm.c
+++ b/drivers/usb/gadget/function/f_ecm.c
@@ -52,6 +52,7 @@ struct f_ecm {
 	struct usb_ep			*notify;
 	struct usb_request		*notify_req;
 	u8				notify_state;
+	atomic_t			notify_count;
 	bool				is_open;
 
 	/* FIXME is_open needs some irq-ish locking
@@ -380,7 +381,7 @@ static void ecm_do_notify(struct f_ecm *ecm)
 	int				status;
 
 	/* notification already in flight? */
-	if (!req)
+	if (atomic_read(&ecm->notify_count))
 		return;
 
 	event = req->buf;
@@ -420,10 +421,10 @@ static void ecm_do_notify(struct f_ecm *ecm)
 	event->bmRequestType = 0xA1;
 	event->wIndex = cpu_to_le16(ecm->ctrl_id);
 
-	ecm->notify_req = NULL;
+	atomic_inc(&ecm->notify_count);
 	status = usb_ep_queue(ecm->notify, req, GFP_ATOMIC);
 	if (status < 0) {
-		ecm->notify_req = req;
+		atomic_dec(&ecm->notify_count);
 		DBG(cdev, "notify --> %d\n", status);
 	}
 }
@@ -448,17 +449,19 @@ static void ecm_notify_complete(struct usb_ep *ep, struct usb_request *req)
 	switch (req->status) {
 	case 0:
 		/* no fault */
+		atomic_dec(&ecm->notify_count);
 		break;
 	case -ECONNRESET:
 	case -ESHUTDOWN:
+		atomic_set(&ecm->notify_count, 0);
 		ecm->notify_state = ECM_NOTIFY_NONE;
 		break;
 	default:
 		DBG(cdev, "event %02x --> %d\n",
 			event->bNotificationType, req->status);
+		atomic_dec(&ecm->notify_count);
 		break;
 	}
-	ecm->notify_req = req;
 	ecm_do_notify(ecm);
 }
 
@@ -907,6 +910,11 @@ static void ecm_unbind(struct usb_configuration *c, struct usb_function *f)
 
 	usb_free_all_descriptors(f);
 
+	if (atomic_read(&ecm->notify_count)) {
+		usb_ep_dequeue(ecm->notify, ecm->notify_req);
+		atomic_set(&ecm->notify_count, 0);
+	}
+
 	kfree(ecm->notify_req->buf);
 	usb_ep_free_request(ecm->notify, ecm->notify_req);
 }
-- 
2.24.1