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

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Date:	Sat, 29 Oct 2011 12:53:29 +0200
From:	David Herrmann <dh.herrmann@...glemail.com>
To:	Arend van Spriel <arend@...adcom.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 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.

>>> +            return -ENODEV;
>>>      }
>>>
>>> +    mutex_lock(&device->readers_lock);
>>> +
>>>      if (!device->open++) {
>>>              /* power on device on adding first reader */
>>>              error = hid_hw_power(device->hid, PM_HINT_FULLON);
>>>
>>
>> regards,
>> dan carpenter
>
> Gr. AvS

Regards
David
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