linux-kernel - RE: [PATCH] usb/core: fix NULL pointer dereference in recursively_mark

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Date:	Thu, 26 Dec 2013 09:08:57 +0000
From:	"Du, ChangbinX" <changbinx.du@...el.com>
To:	'Alan Stern' <stern@...land.harvard.edu>
CC:	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"sarah.a.sharp@...ux.intel.com" <sarah.a.sharp@...ux.intel.com>,
	"Lan, Tianyu" <tianyu.lan@...el.com>,
	"burzalodowa@...il.com" <burzalodowa@...il.com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] usb/core: fix NULL pointer dereference in
 recursively_mark_NOTATTACHED

> > On Tue, 24 Dec 2013, Alan Stern wrote:
> > I think this will fix it.  Take a close look and do some careful testing.
> >
> > Alan Stern
> >
> > Index: usb-3.13/drivers/usb/core/hub.c
> >
> ==========================================================
> > --- usb-3.13.orig/drivers/usb/core/hub.c
> > +++ usb-3.13/drivers/usb/core/hub.c
> > @@ -1622,11 +1622,14 @@ static void hub_disconnect(struct usb_in
> >  	hub->error = 0;
> >  	hub_quiesce(hub, HUB_DISCONNECT);
> >
> > -	usb_set_intfdata (intf, NULL);
> > -
> >  	for (i = 0; i < hdev->maxchild; i++)
> >  		usb_hub_remove_port_device(hub, i + 1);
> > +
> > +	/* Avoid races with recursively_mark_NOTATTACHED() */
> > +	spin_lock_irq(&device_state_lock);
> >  	hub->hdev->maxchild = 0;
> > +	usb_set_intfdata(intf, NULL);
> > +	spin_unlock_irq(&device_state_lock);
> >
> >  	if (hub->hdev->speed == USB_SPEED_HIGH)
> >  		highspeed_hubs--;
> >
> 
> Sorry for late response. Agree with you. I will test your patch carefully and
> let you know the result. Thanks!

I can reproduce issue by adding a delay just after usb_set_intfdata(intf, NULL)
 (echo -1 > bConfigurationValue to trigger hub_dissconnect())without your patch.

After patch applied, cannot reproduce and didn't found any other issue. Patch works well.

Alan, need I update patch to v2 or you will do it?

Du, Changbin
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