coresight: Fix csdev connections initialisation

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 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>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
index ceeaaea..bb20ee9 100644 (file)
--- a/drivers/hwtracing/coresight/coresight.c
+++ b/drivers/hwtracing/coresight/coresight.c
@@ -894,7 +894,7 @@ 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) {
@@ -922,16 +922,20 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
 
        csdev->nr_inport = desc->pdata->nr_inport;
        csdev->nr_outport = desc->pdata->nr_outport;
-       conns = kcalloc(csdev->nr_outport, sizeof(*conns), GFP_KERNEL);
-       if (!conns) {
-               ret = -ENOMEM;
-               goto err_kzalloc_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];
+       /* Initialise connections if there is at least one outport */
+       if (csdev->nr_outport) {
+               conns = kcalloc(csdev->nr_outport, sizeof(*conns), GFP_KERNEL);
+               if (!conns) {
+                       ret = -ENOMEM;
+                       goto err_kzalloc_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;