[PATCH 1/2] coresight: Fix memory leak in acpi_buffer->pointer

[Junhao He <hejunhao3@huawei.com>]

There are memory leaks reported by kmemleak:
...
unreferenced object 0xffff00213c141000 (size 1024):
  comm "systemd-udevd", pid 2123, jiffies 4294909467 (age 6062.160s)
  hex dump (first 32 bytes):
    04 00 00 00 02 00 00 00 18 10 14 3c 21 00 ff ff  ...........<!...
    00 00 00 00 00 00 00 00 03 00 00 00 10 00 00 00  ................
  backtrace:
    [<000000004b7c9001>] __kmem_cache_alloc_node+0x2f8/0x348
    [<00000000b0fc7ceb>] __kmalloc+0x58/0x108
    [<0000000064ff4695>] acpi_os_allocate+0x2c/0x68
    [<000000007d57d116>] acpi_ut_initialize_buffer+0x54/0xe0
    [<0000000024583908>] acpi_evaluate_object+0x388/0x438
    [<0000000017b2e72b>] acpi_evaluate_object_typed+0xe8/0x240
    [<000000005df0eac2>] coresight_get_platform_data+0x1b4/0x988 [coresight]
...

The ACPI buffer memory (buf.pointer) should be freed. But the buffer
is also used after returning from acpi_get_dsd_graph().
Move the temporary variables buf to acpi_coresight_parse_graph(),
and free it before the function return to prevent memory leak.

Fixes: 76ffa5ab5b79 ("coresight: Support for ACPI bindings")
Signed-off-by: Junhao He <hejunhao3@huawei.com>
---
 .../hwtracing/coresight/coresight-platform.c  | 40 ++++++++++++-------
 1 file changed, 26 insertions(+), 14 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-platform.c b/drivers/hwtracing/coresight/coresight-platform.c
index 7d7b641c0a71..9d550f5697fa 100644
--- a/drivers/hwtracing/coresight/coresight-platform.c
+++ b/drivers/hwtracing/coresight/coresight-platform.c
@@ -492,19 +492,18 @@ static inline bool acpi_validate_dsd_graph(const union acpi_object *graph)
 
 /* acpi_get_dsd_graph	- Find the _DSD Graph property for the given device. */
 static const union acpi_object *
-acpi_get_dsd_graph(struct acpi_device *adev)
+acpi_get_dsd_graph(struct acpi_device *adev, struct acpi_buffer *buf)
 {
 	int i;
-	struct acpi_buffer buf = { ACPI_ALLOCATE_BUFFER };
 	acpi_status status;
 	const union acpi_object *dsd;
 
 	status = acpi_evaluate_object_typed(adev->handle, "_DSD", NULL,
-					    &buf, ACPI_TYPE_PACKAGE);
+					    buf, ACPI_TYPE_PACKAGE);
 	if (ACPI_FAILURE(status))
 		return NULL;
 
-	dsd = buf.pointer;
+	dsd = buf->pointer;
 
 	/*
 	 * _DSD property consists tuples { Prop_UUID, Package() }
@@ -555,12 +554,12 @@ acpi_validate_coresight_graph(const union acpi_object *cs_graph)
  * returns NULL.
  */
 static const union acpi_object *
-acpi_get_coresight_graph(struct acpi_device *adev)
+acpi_get_coresight_graph(struct acpi_device *adev, struct acpi_buffer *buf)
 {
 	const union acpi_object *graph_list, *graph;
 	int i, nr_graphs;
 
-	graph_list = acpi_get_dsd_graph(adev);
+	graph_list = acpi_get_dsd_graph(adev, buf);
 	if (!graph_list)
 		return graph_list;
 
@@ -661,22 +660,24 @@ static int acpi_coresight_parse_graph(struct device *dev,
 				      struct acpi_device *adev,
 				      struct coresight_platform_data *pdata)
 {
+	int ret = 0;
 	int i, nlinks;
 	const union acpi_object *graph;
 	struct coresight_connection conn, zero_conn = {};
 	struct coresight_connection *new_conn;
+	struct acpi_buffer buf = { ACPI_ALLOCATE_BUFFER, NULL };
 
-	graph = acpi_get_coresight_graph(adev);
+	graph = acpi_get_coresight_graph(adev, &buf);
 	/*
 	 * There are no graph connections, which is fine for some components.
 	 * e.g., ETE
 	 */
 	if (!graph)
-		return 0;
+		goto free;
 
 	nlinks = graph->package.elements[2].integer.value;
 	if (!nlinks)
-		return 0;
+		goto free;
 
 	for (i = 0; i < nlinks; i++) {
 		const union acpi_object *link = &graph->package.elements[3 + i];
@@ -684,17 +685,28 @@ static int acpi_coresight_parse_graph(struct device *dev,
 
 		conn = zero_conn;
 		dir = acpi_coresight_parse_link(adev, link, &conn);
-		if (dir < 0)
-			return dir;
+		if (dir < 0) {
+			ret = dir;
+			goto free;
+		}
 
 		if (dir == ACPI_CORESIGHT_LINK_MASTER) {
 			new_conn = coresight_add_out_conn(dev, pdata, &conn);
-			if (IS_ERR(new_conn))
-				return PTR_ERR(new_conn);
+			if (IS_ERR(new_conn)) {
+				ret = PTR_ERR(new_conn);
+				goto free;
+			}
 		}
 	}
 
-	return 0;
+free:
+	/*
+	 * When ACPI fails to alloc a buffer, it will free the buffer
+	 * created via ACPI_ALLOCATE_BUFFER and set to NULL.
+	 * ACPI_FREE can handle NULL pointers, so free it directly.
+	 */
+	ACPI_FREE(buf.pointer);
+	return ret;
 }
 
 /*
-- 
2.33.0