Messages in this thread | | | Subject | Re: [PATCH 3/5] coresight: Fix csdev connections initialisation | From | Suzuki K Poulose <> | Date | Wed, 1 Jun 2016 10:30:34 +0100 |
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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
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