linux-kernel - Re: [PATCH v2] usb/core: usb_alloc

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Message-ID: <20160320110031.GA30461@shlinux2.ap.freescale.net>
Date:	Sun, 20 Mar 2016 19:00:31 +0800
From:	Peter Chen <hzpeterchen@...il.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Nicolai Stange <nicstange@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Peter Chen <peter.chen@...escale.com>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Rob Herring <robh@...nel.org>, Arnd Bergmann <arnd@...db.de>,
	Geliang Tang <geliangtang@....com>,
	Stefan Koch <stefan.koch10@...il.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	Oliver Neukum <oneukum@...e.com>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] usb/core: usb_alloc_dev(): fix setting of ->portnum

On Fri, Mar 18, 2016 at 10:13:34AM -0400, Alan Stern wrote:
> On Thu, 17 Mar 2016, Nicolai Stange wrote:
> 
> > With commit 69bec7259853 ("USB: core: let USB device know device node"),
> > the port1 argument of usb_alloc_dev() gets overwritten as follows:
> > 
> >   ... usb_alloc_dev(..., unsigned port1)
> >   {
> >     ...
> >     if (!parent->parent) {
> >       port1 = usb_hcd_find_raw_port_number(..., port1);
> >     }
> >     ...
> >   }
> > 
> > Later on, this now overwritten port1 gets assigned to ->portnum:
> > 
> >   dev->portnum = port1;
> > 
> > However, since xhci_find_raw_port_number() isn't idempotent, the
> > aforementioned commit causes a number of KASAN splats like the following:
> 
> ...
> 
> > Fix this by not overwriting the port1 argument in usb_alloc_dev(), but
> > storing the raw port number as required by OF in an additional variable,
> > raw_port.
> > 
> > Fixes: 69bec7259853 ("USB: core: let USB device know device node")
> > Signed-off-by: Nicolai Stange <nicstange@...il.com>
> > ---
> >  Applicable to linux-next-20160317
> > 
> >  Changes to v1:
> >  - Initialize raw_port with port1
> 
> Acked-by: Alan Stern <stern@...land.harvard.edu>
> 

Thanks for fixing it in time, you are right. My patch would let the
device logical port number equals to device raw port number, but it
is wrong for xhci.

-- 

Best Regards,
Peter Chen