linux-kernel - Re: [PATCH] qcserial: fix a memory leak in qcprobe error path

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Message-ID: <AANLkTilvoCwXuSFK5-jO9ZW6di2LQZQdF_9oFxaLtYTo@mail.gmail.com>
Date:	Wed, 16 Jun 2010 23:07:26 +0800
From:	Axel Lin <axel.lin@...il.com>
To:	Greg KH <greg@...ah.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Matthew Garrett <mjg@...hat.com>,
	Anssi Hannula <anssi.hannula@...il.com>,
	Bernhard Rosenkraenzer <bero@...linux.org>,
	linux-usb@...r.kernel.org
Subject: Re: [PATCH] qcserial: fix a memory leak in qcprobe error path

hi Greg,

2010/6/15 Greg KH <greg@...ah.com>:
> On Tue, Jun 08, 2010 at 03:29:23PM +0800, Axel Lin wrote:
>> In current implemtation, the "data" is not kfreed in qcprobe error path.
>> This patch moves the memory allocation a little bit latter and only
>> allocate memory when no error is detected in previous checking.
>
> Yeah, but it's now pretty messy.
>
>> --- a/drivers/usb/serial/qcserial.c
>> +++ b/drivers/usb/serial/qcserial.c
>> @@ -109,13 +109,6 @@ static int qcprobe(struct usb_serial *serial, const struct usb_device_id *id)
>>       ifnum = intf->desc.bInterfaceNumber;
>>       dbg("This Interface = %d", ifnum);
>>
>> -     data = serial->private = kzalloc(sizeof(struct usb_wwan_intf_private),
>> -                                      GFP_KERNEL);
>> -     if (!data)
>> -             return -ENOMEM;
>> -
>> -     spin_lock_init(&data->susp_lock);
>> -
>
> Moving this to the end is fine.
>
>> @@ -140,7 +135,7 @@ static int qcprobe(struct usb_serial *serial, const struct usb_device_id *id)
>>                                       retval);
>>                               retval = -ENODEV;
>>                       }
>> -                     return retval;
>> +                     goto out;
>
> But this doesn't need to be changed, right?
> Or this.
>
>>               }
>>               break;
>>
>> @@ -156,17 +151,26 @@ static int qcprobe(struct usb_serial *serial, const struct usb_device_id *id)
>>                                       retval);
>>                               retval = -ENODEV;
>>                       }
>> -                     return retval;
>> +                     goto out;
>
> Or this?
>
>>               }
>>               break;
>>
>>       default:
>>               dev_err(&serial->dev->dev,
>>                       "unknown number of interfaces: %d\n", nintf);
>> -             return -ENODEV;
>
> Hm. maybe.
>
>>       }
>>
>> -     return retval;
>> +out:
>> +     if (retval)
>> +             return retval;
>> +
>> +     data = serial->private = kzalloc(sizeof(struct usb_wwan_intf_private),
>> +                                      GFP_KERNEL);
>> +     if (!data)
>> +             return -ENOMEM;
>> +
>> +     spin_lock_init(&data->susp_lock);
>> +     return 0;
>
> I guess it's ok, I just don't like doing data initialization on the
> "out" path, it's messy.
>
> Care to neaten this up a bit more and resend it?  Perhaps just free the
> memory on the error path instead of moving it later on?

I will send a revised patch that just free the memory on the error path.
Thanks for the review.

Axel
>
> thanks,
>
> greg k-h
>
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