linux-kernel - Re: [PATCH] staging: ks7010_sdio: fix NULL pointer dereference and memory leak

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Message-ID: <466bc78a-8cc5-a693-278b-da34194a35b2@embeddedor.com>
Date:   Thu, 12 Apr 2018 10:14:30 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Colin King <colin.king@...onical.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: ks7010_sdio: fix NULL pointer dereference and
 memory leak

Hi Dan,

On 04/12/2018 10:08 AM, Dan Carpenter wrote:
> I added Colin to the Cc list.
> 
> On Thu, Apr 12, 2018 at 09:30:09AM -0500, Gustavo A. R. Silva wrote:
>> priv is being dereferenced when it is still null, hence there is an
>> explicit null pointer dereference at line 935: free_netdev(priv->net_dev)
>>
>> Also, memory allocated for netdev at line 854:
>> netdev = alloc_etherdev(sizeof(*priv));
>> is not being free'd, hence there is a memory leak.
>>
>> Fix this by null checking priv before dererefencing it and free netdev
>> before return.
>>
>> Addresses-Coverity-ID: 1467844 ("Explicit null dereferenced")
>> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
>> ---
>>   drivers/staging/ks7010/ks7010_sdio.c | 8 ++++++--
>>   1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/staging/ks7010/ks7010_sdio.c b/drivers/staging/ks7010/ks7010_sdio.c
>> index b8f55a1..f5d4c62 100644
>> --- a/drivers/staging/ks7010/ks7010_sdio.c
>> +++ b/drivers/staging/ks7010/ks7010_sdio.c
>> @@ -932,8 +932,12 @@ static int ks7010_sdio_probe(struct sdio_func *func,
>>   	return 0;
>>   
>>    err_free_netdev:
>> -	free_netdev(priv->net_dev);
>> -	card->priv = NULL;
>> +	if (priv) {
>> +		free_netdev(priv->net_dev);
>> +		card->priv = NULL;
> 
> This isn't required because the next thing we do to card is kfree(card).
> 

I got it.

>> +	} else {
>> +		free_netdev(netdev);
>> +	}
> 
> 
> That's too complicated.  Just do:
> 
> err_free_netdev:
> 	free_netdev(net_dev);
> 
> err_release_irq:
> 	...
> 
> Please send a v2 patch.
> 

Sure thing, I'll send it shortly.

Thanks for the feedback.
--
Gustavo