linux-kernel - Re: [PATCH v6 4/4] usb: gadget: udc-core: independent registration of gadgets and gadget drivers

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20151123074030.GC16321@shlinux2>
Date:	Mon, 23 Nov 2015 15:40:31 +0800
From:	Peter Chen <peter.chen@...escale.com>
To:	Alan Stern <stern@...land.harvard.edu>
CC:	Marek Szyprowski <m.szyprowski@...sung.com>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Ruslan Bilovol <ruslan.bilovol@...il.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH v6 4/4] usb: gadget: udc-core: independent registration
 of gadgets and gadget drivers

On Fri, Nov 20, 2015 at 11:27:36AM -0500, Alan Stern wrote:
> On Fri, 20 Nov 2015, Marek Szyprowski wrote:
> 
> > From: Ruslan Bilovol <ruslan.bilovol@...il.com>
> > 
> > Change behavior during registration of gadgets and
> > gadget drivers in udc-core. Instead of previous
> > approach when for successful probe of usb gadget driver
> > at least one usb gadget should be already registered
> > use another one where gadget drivers and gadgets
> > can be registered in udc-core independently.
> > 
> > Independent registration of gadgets and gadget drivers
> > is useful for built-in into kernel gadget and gadget
> > driver case - because it's possible that gadget is
> > really probed only on late_init stage (due to deferred
> > probe) whereas gadget driver's probe is silently failed
> > on module_init stage due to no any UDC added.
> > 
> > Also it is useful for modules case - now there is no
> > difference what module to insert first: gadget module
> > or gadget driver one.
> > 
> > Tested-by: Maxime Ripard <maxime.ripard@...e-electrons.com>
> > Signed-off-by: Ruslan Bilovol <ruslan.bilovol@...il.com>
> > [simplified code as requested by Alan Stern and Felipe Balbi]
> > Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
> 
> ...
> 
> > @@ -475,9 +492,16 @@ void usb_del_gadget_udc(struct usb_gadget *gadget)
> >  	list_del(&udc->list);
> >  	mutex_unlock(&udc_lock);
> >  
> > -	if (udc->driver)
> > +	if (udc->driver) {
> > +		struct usb_gadget_driver *driver = udc->driver;
> > +
> >  		usb_gadget_remove_driver(udc);
> >  
> > +		mutex_lock(&udc_lock);
> > +		list_add(&driver->pending, &gadget_driver_pending_list);
> > +		mutex_unlock(&udc_lock);
> > +	}
> 
> It looks like there is a race here with usb_gadget_unregister_driver().  
> Would it be okay to hold the udc_lock mutex throughout the whole "if"  
> statement?
> 

+1

In fact, only one mutex_lock/mutex_unlock is needed at this function.
-- 

Best Regards,
Peter Chen
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/