coresight: Fix support for sparsely populated ports

On some systems the firmware may not describe all the ports
connected to a component (e.g, for security reasons). This
could be especially problematic for "funnels" where we could
end up in modifying memory beyond the allocated space for
refcounts.

e.g, for a funnel with input ports listed 0, 3, 5, nr_inport = 3.
However the we could access refcnts[5] while checking for
references, like :

[ 526.110401] ==================================================================
[ 526.117988] BUG: KASAN: slab-out-of-bounds in funnel_enable+0x54/0x1b0
[ 526.124706] Read of size 4 at addr ffffff8135f9549c by task bash/1114
[ 526.131324]
[ 526.132886] CPU: 3 PID: 1114 Comm: bash Tainted: G S 5.4.25 #232
[ 526.140397] Hardware name: Qualcomm Technologies, Inc. SC7180 IDP (DT)
[ 526.147113] Call trace:
[ 526.149653] dump_backtrace+0x0/0x188
[ 526.153431] show_stack+0x20/0x2c
[ 526.156852] dump_stack+0xdc/0x144
[ 526.160370] print_address_description+0x3c/0x494
[ 526.165211] __kasan_report+0x144/0x168
[ 526.169170] kasan_report+0x10/0x18
[ 526.172769] check_memory_region+0x1a4/0x1b4
[ 526.177164] __kasan_check_read+0x18/0x24
[ 526.181292] funnel_enable+0x54/0x1b0
[ 526.185072] coresight_enable_path+0x104/0x198
[ 526.189649] coresight_enable+0x118/0x26c

...

[ 526.237782] Allocated by task 280:
[ 526.241298] __kasan_kmalloc+0xf0/0x1ac
[ 526.245249] kasan_kmalloc+0xc/0x14
[ 526.248849] __kmalloc+0x28c/0x3b4
[ 526.252361] coresight_register+0x88/0x250
[ 526.256587] funnel_probe+0x15c/0x228
[ 526.260365] dynamic_funnel_probe+0x20/0x2c
[ 526.264679] amba_probe+0xbc/0x158
[ 526.268193] really_probe+0x144/0x408
[ 526.271970] driver_probe_device+0x70/0x140

...

[ 526.316810]
[ 526.318364] Freed by task 0:
[ 526.321344] (stack is not available)
[ 526.325024]
[ 526.326580] The buggy address belongs to the object at ffffff8135f95480
[ 526.326580] which belongs to the cache kmalloc-128 of size 128
[ 526.339439] The buggy address is located 28 bytes inside of
[ 526.339439] 128-byte region [ffffff8135f95480, ffffff8135f95500)
[ 526.351399] The buggy address belongs to the page:
[ 526.356342] page:ffffffff04b7e500 refcount:1 mapcount:0 mapping:ffffff814b00c380 index:0x0 compound_mapcount: 0
[ 526.366711] flags: 0x4000000000010200(slab|head)
[ 526.371475] raw: 4000000000010200 ffffffff05034008 ffffffff0501eb08 ffffff814b00c380
[ 526.379435] raw: 0000000000000000 0000000000190019 00000001ffffffff 0000000000000000
[ 526.387393] page dumped because: kasan: bad access detected
[ 526.393128]
[ 526.394681] Memory state around the buggy address:
[ 526.399619] ffffff8135f95380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 526.407046] ffffff8135f95400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 526.414473] >ffffff8135f95480: 04 fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 526.421900] ^
[ 526.426029] ffffff8135f95500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 526.433456] ffffff8135f95580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 526.440883] ==================================================================

To keep the code simple, we now track the maximum number of
possible input/output connections to/from this component
@ nr_inport and nr_outport in platform_data, respectively.
Thus the output connections could be sparse and code is
adjusted to skip the unspecified connections.

Cc: Mathieu Poirier <[e-mail]>
Cc: Mike Leach <[e-mail]>
Reported-by: Sai Prakash Ranjan <[e-mail]>
Tested-by: Sai Prakash Ranjan <[e-mail]>
Tested-by: Stephen Boyd <[e-mail]>
Signed-off-by: Suzuki K Poulose <[e-mail]>
Signed-off-by: Mathieu Poirier <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/hwtracing/coresight/coresight-platform.c

···
 					  int *nr_inport, int *nr_outport)
 {
 	struct device_node *ep = NULL;
+	struct of_endpoint endpoint;
 	int in = 0, out = 0;
 
 	do {
···
 		if (!ep)
 			break;
 
-		if (of_coresight_legacy_ep_is_input(ep))
-			in++;
-		else
-			out++;
+		if (of_graph_parse_endpoint(ep, &endpoint))
+			continue;
+
+		if (of_coresight_legacy_ep_is_input(ep)) {
+			in = (endpoint.port + 1 > in) ?
+				endpoint.port + 1 : in;
+		} else {
+			out = (endpoint.port + 1) > out ?
+				endpoint.port + 1 : out;
+		}
 
 	} while (ep);
 
···
 {
 	int i = 0;
 	struct device_node *ep = NULL;
+	struct of_endpoint endpoint;
 
-	while ((ep = of_graph_get_next_endpoint(port_parent, ep)))
-		i++;
+	while ((ep = of_graph_get_next_endpoint(port_parent, ep))) {
+		/* Defer error handling to parsing */
+		if (of_graph_parse_endpoint(ep, &endpoint))
+			continue;
+		if (endpoint.port + 1 > i)
+			i = endpoint.port + 1;
+	}
+
 	return i;
 }
 
···
  * Parses the local port, remote device name and the remote port.
  *
  * Returns :
- *	 1	- If the parsing is successful and a connection record
- *		  was created for an output connection.
  *	 0	- If the parsing completed without any fatal errors.
  *	-Errno	- Fatal error, abort the scanning.
  */
 static int of_coresight_parse_endpoint(struct device *dev,
 				       struct device_node *ep,
-				       struct coresight_connection *conn)
+				       struct coresight_platform_data *pdata)
 {
 	int ret = 0;
 	struct of_endpoint endpoint, rendpoint;
···
 	struct device_node *rep = NULL;
 	struct device *rdev = NULL;
 	struct fwnode_handle *rdev_fwnode;
+	struct coresight_connection *conn;
 
 	do {
 		/* Parse the local port details */
···
 			break;
 		}
 
+		conn = &pdata->conns[endpoint.port];
+		if (conn->child_fwnode) {
+			dev_warn(dev, "Duplicate output port %d\n",
+				 endpoint.port);
+			ret = -EINVAL;
+			break;
+		}
 		conn->outport = endpoint.port;
 		/*
 		 * Hold the refcount to the target device. This could be
···
 		conn->child_fwnode = fwnode_handle_get(rdev_fwnode);
 		conn->child_port = rendpoint.port;
 		/* Connection record updated */
-		ret = 1;
 	} while (0);
 
 	of_node_put(rparent);
···
 					  struct coresight_platform_data *pdata)
 {
 	int ret = 0;
-	struct coresight_connection *conn;
 	struct device_node *ep = NULL;
 	const struct device_node *parent = NULL;
 	bool legacy_binding = false;
···
 		dev_warn_once(dev, "Uses obsolete Coresight DT bindings\n");
 	}
 
-	conn = pdata->conns;
-
 	/* Iterate through each output port to discover topology */
 	while ((ep = of_graph_get_next_endpoint(parent, ep))) {
 		/*
···
 		if (legacy_binding && of_coresight_legacy_ep_is_input(ep))
 			continue;
 
-		ret = of_coresight_parse_endpoint(dev, ep, conn);
-		switch (ret) {
-		case 1:
-			conn++;		/* Fall through */
-		case 0:
-			break;
-		default:
+		ret = of_coresight_parse_endpoint(dev, ep, pdata);
+		if (ret)
 			return ret;
-		}
 	}
 
 	return 0;
···
 		 *    coresight_remove_match().
 		 */
 		conn->child_fwnode = fwnode_handle_get(&r_adev->fwnode);
+	} else if (dir == ACPI_CORESIGHT_LINK_SLAVE) {
+		/*
+		 * We are only interested in the port number
+		 * for the input ports at this component.
+		 * Store the port number in child_port.
+		 */
+		conn->child_port = fields[0].integer.value;
+	} else {
+		/* Invalid direction */
+		return -EINVAL;
 	}
 
 	return dir;
···
 			return dir;
 
 		if (dir == ACPI_CORESIGHT_LINK_MASTER) {
-			pdata->nr_outport++;
+			if (ptr->outport > pdata->nr_outport)
+				pdata->nr_outport = ptr->outport;
 			ptr++;
 		} else {
-			pdata->nr_inport++;
+			WARN_ON(pdata->nr_inport == ptr->child_port);
+			/*
+			 * We do not track input port connections for a device.
+			 * However we need the highest port number described,
+			 * which can be recorded now and reuse this connection
+			 * record for an output connection. Hence, do not move
+			 * the ptr for input connections
+			 */
+			if (ptr->child_port > pdata->nr_inport)
+				pdata->nr_inport = ptr->child_port;
 		}
 	}
 
···
 		return rc;
 
 	/* Copy the connection information to the final location */
-	for (i = 0; i < pdata->nr_outport; i++)
-		pdata->conns[i] = conns[i];
+	for (i = 0; conns + i < ptr; i++) {
+		int port = conns[i].outport;
+
+		/* Duplicate output port */
+		WARN_ON(pdata->conns[port].child_fwnode);
+		pdata->conns[port] = conns[i];
+	}
 
 	devm_kfree(&adev->dev, conns);
 	return 0;

drivers/hwtracing/coresight/coresight.c

···
 	for (i = 0; i < i_csdev->pdata->nr_outport; i++) {
 		conn = &i_csdev->pdata->conns[i];
 
+		/* Skip the port if FW doesn't describe it */
+		if (!conn->child_fwnode)
+			continue;
 		/* We have found at least one orphan connection */
 		if (conn->child_dev == NULL) {
 			/* Does it match this newly added device? */
···
 	for (i = 0; i < csdev->pdata->nr_outport; i++) {
 		struct coresight_connection *conn = &csdev->pdata->conns[i];
 
+		if (!conn->child_fwnode)
+			continue;
 		conn->child_dev =
 			coresight_find_csdev_by_fwnode(conn->child_fwnode);
 		if (conn->child_dev) {
···
 	for (i = 0; i < iterator->pdata->nr_outport; i++) {
 		conn = &iterator->pdata->conns[i];
 
-		if (conn->child_dev == NULL)
+		if (conn->child_dev == NULL || conn->child_fwnode == NULL)
 			continue;
 
 		if (csdev->dev.fwnode == conn->child_fwnode) {

include/linux/coresight.h

···
 };
 
 /**
- * struct coresight_platform_data - data harvested from the DT specification
- * @nr_inport:	number of input ports for this component.
- * @nr_outport:	number of output ports for this component.
- * @conns:	Array of nr_outport connections from this component
+ * struct coresight_platform_data - data harvested from the firmware
+ * specification.
+ *
+ * @nr_inport:	Number of elements for the input connections.
+ * @nr_outport:	Number of elements for the output connections.
+ * @conns:	Sparse array of nr_outport connections from this component.
  */
 struct coresight_platform_data {
 	int nr_inport;