linux-kernel - [PATCH v3 3/7] coresight: Fix csdev connections initialisation

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Message-Id: <1466525454-14702-4-git-send-email-suzuki.poulose@arm.com>
Date:	Tue, 21 Jun 2016 17:10:50 +0100
From:	Suzuki K Poulose <suzuki.poulose@....com>
To:	mathieu.poirier@...aro.org
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Suzuki K Poulose <suzuki.poulose@....com>
Subject: [PATCH v3 3/7] 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@...aro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
---
 drivers/hwtracing/coresight/coresight.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
index d08d1ab..7ba9561 100644
--- a/drivers/hwtracing/coresight/coresight.c
+++ b/drivers/hwtracing/coresight/coresight.c
@@ -893,7 +893,7 @@ 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) {
@@ -921,16 +921,20 @@ 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;
-- 
1.9.1