linux-kernel - Re: [PATCH 3/5] drivers/hid/hid-roccat.c: eliminate a null pointer dereference

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Date:	Mon, 31 Oct 2011 10:22:53 +0100
From:	"Arend van Spriel" <arend@...adcom.com>
To:	"David Herrmann" <dh.herrmann@...glemail.com>
cc:	"Dan Carpenter" <dan.carpenter@...cle.com>,
	"Julia Lawall" <julia@...u.dk>, "Jiri Kosina" <jkosina@...e.cz>,
	"kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/5] drivers/hid/hid-roccat.c: eliminate a null
 pointer dereference

On 10/29/2011 12:53 PM, David Herrmann wrote:
> On Sat, Oct 29, 2011 at 11:36 AM, Arend van Spriel <arend@...adcom.com> wrote:
>> On 10/29/2011 08:24 AM, Dan Carpenter wrote:
>>> On Sat, Oct 29, 2011 at 01:58:15AM +0200, Julia Lawall wrote:
>>>> diff --git a/drivers/hid/hid-roccat.c b/drivers/hid/hid-roccat.c
>>>> index 2596321..36a28b8 100644
>>>> --- a/drivers/hid/hid-roccat.c
>>>> +++ b/drivers/hid/hid-roccat.c
>>>> @@ -163,14 +163,15 @@ static int roccat_open(struct inode *inode, struct file *file)
>>>>
>>>>      device = devices[minor];
>>>>
>>>> -    mutex_lock(&device->readers_lock);
>>>> -
>>>>      if (!device) {
>>>>              pr_emerg("roccat device with minor %d doesn't exist\n", minor);
>>>> -            error = -ENODEV;
>>>> -            goto exit_err;
>>>> +            kfree(reader);
>>>> +            mutex_lock(&devices_lock);
>>>
>>> Typo.  mutex_unlock() instead of mutex_lock().
>>
>> This is no typo, but simply wrong. Remove the mutex_lock() as we are
>> leaving the function here in error flow.
> 
> No, this one is definitely needed. Its devices_lock, not
> device->readers_lock! And devices_lock is locked before so we need to
> unlock it if we return in this branch.

You are right. I missed that. As usual Dan's eye is sharper ;-)

Gr. AvS


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