linux-kernel - Re: [PATCH] reset: fix potential null pointer dereference on pointer dev

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Date:   Fri, 10 May 2019 10:16:47 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     Philipp Zabel <p.zabel@...gutronix.de>
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH] reset: fix potential null pointer dereference on pointer
 dev

On 10/05/2019 10:14, Philipp Zabel wrote:
> Hi Colin,
> 
> [added Bartosz to Cc:]
> 
> On Thu, 2019-05-09 at 17:00 +0100, Colin King wrote:
>> From: Colin Ian King <colin.king@...onical.com>
>>
>> Pointer dev is being dereferenced when passed to the inlined
>> functon dev_name, however, dev is later being null checked.
>> Thus there is a potential null pointer dereference on a null
>> dev. Fix this by performing the null check on dev before
>> dereferencing it.
>>
>> Addresses-Coverity: ("Dereference before null check")
>> Fixes: 6691dffab0ab ("reset: add support for non-DT systems")
>> Signed-off-by: Colin Ian King <colin.king@...onical.com>
>> ---
>>  drivers/reset/core.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/reset/core.c b/drivers/reset/core.c
>> index 81ea77cba123..83f1a1d5ee67 100644
>> --- a/drivers/reset/core.c
>> +++ b/drivers/reset/core.c
>> @@ -691,12 +691,13 @@ __reset_control_get_from_lookup(struct device *dev, const char *con_id,
>>  {
>>  	const struct reset_control_lookup *lookup;
>>  	struct reset_controller_dev *rcdev;
>> -	const char *dev_id = dev_name(dev);
>> +	const char *dev_id;
>>  	struct reset_control *rstc = NULL;
>>  
>>  	if (!dev)
>>  		return ERR_PTR(-EINVAL);
> 
> Thank you for the patch. I think this check should be removed instead,
> though, as __reset_control_get_from_lookup is only ever called from
> __reset_control_get, right after checking dev->of_node. So dev can not
> be NULL here.

Good point, I totally overlooked that. I'll send a V2 shortly.

> 
> regards
> Philipp
>