linux-kernel - Re: [PATCH][V2] usb: isp1760: fix null dereference if kzalloc returns null

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Date:	Tue, 02 Jun 2015 18:41:37 +0300
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
Cc:	Colin King <colin.king@...onical.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Felipe Balbi <balbi@...com>,
	Sudeep Holla <sudeep.holla@....com>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH][V2] usb: isp1760: fix null dereference if kzalloc returns null

On Monday 01 June 2015 16:51:30 Sergei Shtylyov wrote:
> Hello.
> 
> On 6/1/2015 1:43 AM, Colin King wrote:
> > From: Colin Ian King <colin.king@...onical.com>
> > 
> > If kzalloc returns null then isp1760_ep_alloc_request performs
> > a null pointer dereference on req. Check for null to avoid this.
> 
> I told you there's no dereference and yet you're repeating it again. :-(

How about

"isp1760_ep_alloc_request allocates a structure with kzalloc without checking 
for NULL and then returns a pointer to one of the structure fields. As the 
field happens to be the first in the structure the caller can properly check 
for NULL, but this is risky if the structure layout is changed later. Add an 
explicit NULL check for the kzalloc return value."

> > a null pointer dereference on req. Check for null to avoid this.
> >
> > Detected with smatch static analysis:
> > 
> > drivers/usb/isp1760/isp1760-udc.c:816 isp1760_ep_alloc_request()
> > 
> >    error: potential null dereference 'req'.  (kzalloc returns null)
> > 
> > Signed-off-by: Colin Ian King <colin.king@...onical.com>

-- 
Regards,

Laurent Pinchart

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