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

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Message-ID: <556B8E0D.8020703@canonical.com>
Date:	Sun, 31 May 2015 23:41:17 +0100
From:	Colin Ian King <colin.king@...onical.com>
To:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Felipe Balbi <balbi@...com>,
	Sudeep Holla <sudeep.holla@....com>, linux-usb@...r.kernel.org
CC:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: isp1760: fix null dereference if kzalloc returns
 null

On 31/05/15 23:15, Sergei Shtylyov wrote:
> Hello.
> 
> On 06/01/2015 01:00 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 deference on req.
> 
>    Dereference, not "deference".

Shall I send v2 for this stupid typo then?

>    No, it doesn't. It calculates the address of the
> 'isp1760_request::req' instead, there's no dereference per se. I suppose
> this is a first member of the structure, so this function should work
> correctly in any case.

Well, for now it's the first member, but can we assume that will apply
forever? As it stands, other *_alloc_request() functions in all the
other usb drivers check for the NULL, so this fix just aligns the code
with all of these other drivers.


> 
>> 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)
> 
>    Well, the change won't hurt anyway, makes things clearer.
> 
>> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> 
> WBR, Sergei
> 

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