linux-kernel - Re: [PATCH v2 4/9] coresight: Fix csdev connections initialisation

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Date:	Mon, 13 Jun 2016 08:37:35 -0600
From:	Mathieu Poirier <mathieu.poirier@...aro.org>
To:	Suzuki K Poulose <Suzuki.Poulose@....com>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 4/9] coresight: Fix csdev connections initialisation

On 13 June 2016 at 02:54, Suzuki K Poulose <Suzuki.Poulose@....com> wrote:
> On 12/06/16 21:39, Mathieu Poirier wrote:
>>
>> On 6 June 2016 at 03:11, Suzuki K Poulose <suzuki.poulose@....com> wrote:
>>>
>>> This is a cleanup patch.
>>>
>>> coresight_device->conns holds an array to point to the devices
>>> connected to the OUT ports of a component. Sinks, e.g ETR, do not
>>> have an OUT port (nr_outport = 0), as it streams the trace to
>>> memory via AXI.
>>>
>>> At coresight_register() we do :
>>>
>>>          conns = kcalloc(csdev->nr_outport, sizeof(*conns), GFP_KERNEL);
>>>          if (!conns) {
>>>                  ret = -ENOMEM;
>>>                  goto err_kzalloc_conns;
>>>          }
>>>
>>> For ETR, since the total size requested for kcalloc is zero, the return
>>> value is, ZERO_SIZE_PTR ( != NULL). Hence, csdev->conns = ZERO_SIZE_PTR
>>> which cannot be verified later to contain a valid pointer. The code which
>>> accesses the csdev->conns is bounded by the csdev->nr_outport check,
>>> hence we don't try to dereference the ZERO_SIZE_PTR. This patch cleans
>>> up the csdev->conns and csdev->refcnt, initialisation to make sure we
>>
>>
>> This patch no longer deals with csdev->refcnt.
>
>
> Ok, fill fix that. Btw, do we need that check ? I am tempted to keep it
> there,
> just to make sure we don't end up in something similar in the future.

If it becomes an issue in the future we'll know what to do :o)

Thanks,
Mathieu

>
> Cheers
> Suzuki