[PATCH net] usbnet: Fix memory leak in usbnet_disconnect()

[Peilin Ye <yepeilin.cs@gmail.com>]

From: Peilin Ye <peilin.ye@bytedance.com>

Currently usbnet_disconnect() unanchors and frees all deferred URBs
using usb_scuttle_anchored_urbs(), which does not free urb->context,
causing a memory leak as reported by syzbot.

Use a usb_get_from_anchor() while loop instead, similar to what we did
in commit 19cfe912c37b ("Bluetooth: btusb: Fix memory leak in
play_deferred").  Also free urb->sg.

Reported-and-tested-by: syzbot+dcd3e13cf4472f2e0ba1@syzkaller.appspotmail.com
Fixes: 69ee472f2706 ("usbnet & cdc-ether: Autosuspend for online devices")
Fixes: 638c5115a794 ("USBNET: support DMA SG")
Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>
---
Hi all,

I think we may have similar issues at other usb_scuttle_anchored_urbs()
call sites.  Since urb->context is (void *), should we pass a "destructor"
callback to usb_scuttle_anchored_urbs(), or replace this function with
usb_get_from_anchor() loops like this patch does?

Please advise, thanks!
Peilin Ye

 drivers/net/usb/usbnet.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index fd399a8ed973..64a9a80b2309 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -1598,6 +1598,7 @@ void usbnet_disconnect (struct usb_interface *intf)
 	struct usbnet		*dev;
 	struct usb_device	*xdev;
 	struct net_device	*net;
+	struct urb		*urb;
 
 	dev = usb_get_intfdata(intf);
 	usb_set_intfdata(intf, NULL);
@@ -1614,7 +1615,11 @@ void usbnet_disconnect (struct usb_interface *intf)
 	net = dev->net;
 	unregister_netdev (net);
 
-	usb_scuttle_anchored_urbs(&dev->deferred);
+	while ((urb = usb_get_from_anchor(&dev->deferred))) {
+		dev_kfree_skb(urb->context);
+		kfree(urb->sg);
+		usb_free_urb(urb);
+	}
 
 	if (dev->driver_info->unbind)
 		dev->driver_info->unbind(dev, intf);
-- 
2.20.1