lkml.org 
[lkml]   [2016]   [Jun]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 3/5] coresight: Fix csdev connections initialisation
From
Date
On 31/05/16 18:55, Mathieu Poirier wrote:
> On 31 May 2016 at 05:57, Suzuki K Poulose <suzuki.poulose@arm.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 initialise it properly(i.e, either NULL or valid conns array).
>>
>> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
>> ---
>> drivers/hwtracing/coresight/coresight.c | 42 +++++++++++++++++++--------------
>> 1 file changed, 24 insertions(+), 18 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
>> index 0fdaaf4..8410420 100644
>> --- a/drivers/hwtracing/coresight/coresight.c
>> +++ b/drivers/hwtracing/coresight/coresight.c
>> @@ -890,7 +890,7 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
>> int nr_refcnts = 1;
>> atomic_t *refcnts = NULL;
>> struct coresight_device *csdev;
>> - struct coresight_connection *conns;
>> + struct coresight_connection *conns = NULL;
>>
>> csdev = kzalloc(sizeof(*csdev), GFP_KERNEL);
>> if (!csdev) {
>> @@ -908,29 +908,35 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
>> nr_refcnts = desc->pdata->nr_outport;
>> }
>>
>> - refcnts = kcalloc(nr_refcnts, sizeof(*refcnts), GFP_KERNEL);
>> - if (!refcnts) {
>> - ret = -ENOMEM;
>> - goto err_kzalloc_refcnts;
>> - }
>> + if (nr_refcnts) {
>
> Did you manage to find a usecase where "nr_refcnts == 0" ? Since
> components have at least one port this condition will always be true.

No, I didn't find one. While I was fixing the nr_outport, I thought it would
be good to check the refcnts as well.

>>
>> - csdev->conns = conns;
>> + for (i = 0; i < csdev->nr_outport; i++) {
>> + conns[i].outport = desc->pdata->outports[i];
>> + conns[i].child_name = desc->pdata->child_names[i];
>> + conns[i].child_port = desc->pdata->child_ports[i];
>> + }
>> +
>> + csdev->conns = conns;
>
> The purpose of your patch is to correctly initialise csdev->conns to
> NULL if there is no output port to speak of. As such shouldn't the
> above statement be out of the if (csdev->nr_outport) {} ?.

Not necessarily. We do a kzalloc() for csdev, which implies csdev->conns
is already NULL. I can move the code to make that explicit assignment.

>
> I'm also getting a couple of checkpatch.pl warnings on this patch.

I can fix those warnings. I ignored them initially, as it was for the length of the comment.

Cheers
Suzuki

\
 
 \ /
  Last update: 2016-06-01 11:41    [W:0.097 / U:0.308 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site