linux-kernel - Re: [PATCH 1/1] Free fw_priv in fw_create

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Message-ID: <CALN+fr1Nke3kgEpJbb8fbzAd=dB_KhKP71rZRpm7TjOmkE5Jwg@mail.gmail.com>
Date:	Wed, 31 Aug 2011 01:16:24 +0530
From:	Rajan Aggarwal <rajan.aggarwal85@...il.com>
To:	Greg KH <gregkh@...e.de>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] Free fw_priv in fw_create_instance

Hi,


On Wed, Aug 31, 2011 at 12:49 AM, Greg KH <gregkh@...e.de> wrote:
> On Wed, Aug 31, 2011 at 12:36:32AM +0530, Rajan Aggarwal wrote:
>> fw_priv is not being freed in some of the error scenarios in
>> fw_create_instance.
>
> Not true.
>
>> This patch makes sure that this is kfreed properly in all error
>> situations in the fw_create_instance logic where it is required.
>
> Nope, this will cause a double-free to happen.

>From what you say, the only suspicious line seems to be the following
assignment:
f_dev = &fw_priv->dev;
However, I cannot make out how this can be freed by device_del or
put_device as I
don't see the logic anywhere where f_dev is decremented to get the
address of fw_priv.

>
>> Signed-off-by: Rajan Aggarwal <rajan.aggarwal85@...il.com>
>> ---
>>  drivers/base/firmware_class.c |    1 +
>>  1 files changed, 1 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
>> index 06ed6b4..3ddbc48 100644
>> --- a/drivers/base/firmware_class.c
>> +++ b/drivers/base/firmware_class.c
>> @@ -497,6 +497,7 @@ err_del_dev:
>>       device_del(f_dev);
>>  err_put_dev:
>>       put_device(f_dev);
>> +     kfree(fw_priv);
>
> Did you test this patch out?  What happened when you tested it?
>
> How did you find this "problem"?
>
> Care to look a bit closer at the code?
>
> I'd give you a hint, but it's more sporting this way :)
>

I was looking at some bluetooth code and went into the request_firmware API
and saw this.
I was browsing through this code and this looked like a problem.
I have just started using git and decided to post this email.

But I still don't see how the fw_priv can be freed. :)
There might be some place in kobject where this decrementation is
happening but I
must be missing something.

> thanks,
>
> greg k-h
>
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