Patch "HID: wacom: Have wacom_tpc_irq guard against possible NULL dereference" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

HID: wacom: Have wacom_tpc_irq guard against possible NULL dereference

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
hid-wacom-have-wacom_tpc_irq-guard-against-possible-null-dereference.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Jason Gerecke <[email protected]>
Date: Tue, 25 Apr 2017 11:29:56 -0700
Subject: HID: wacom: Have wacom_tpc_irq guard against possible NULL dereference

From: Jason Gerecke <[email protected]>

commit 2ac97f0f6654da14312d125005c77a6010e0ea38 upstream.

The following Smatch complaint was generated in response to commit 2a6cdbd ("HID: wacom: Introduce new 'touch_input' device"):

    drivers/hid/wacom_wac.c:1586 wacom_tpc_irq()
             error: we previously assumed 'wacom->touch_input' could be null (see line 1577)

The 'touch_input' and 'pen_input' variables point to the 'struct input_dev' used for relaying touch and pen events to userspace, respectively. If a device does not have a touch interface or pen interface, the associated input variable is NULL. The 'wacom_tpc_irq()' function is responsible for forwarding input reports to a more-specific IRQ handler function. An unknown report could theoretically be mistaken as e.g. a touch report on a device which does not have a touch interface. This can be prevented by only calling the pen/touch functions are called when the pen/touch pointers are valid.

---
 drivers/hid/wacom_wac.c |   47 ++++++++++++++++++++++++-----------------------
 1 file changed, 24 insertions(+), 23 deletions(-)

@@ -1400,37 +1400,38 @@ static int wacom_tpc_irq(struct wacom_wa
 {
 	unsigned char *data = wacom->data;
 
-	if (wacom->pen_input)
+	if (wacom->pen_input) {
 		dev_dbg(wacom->pen_input->dev.parent,
 			"%s: received report #%d\n", __func__, data[0]);
-	else if (wacom->touch_input)
+
+		if (len == WACOM_PKGLEN_PENABLED ||
+		    data[0] == WACOM_REPORT_PENABLED)
+			return wacom_tpc_pen(wacom);
+	}
+	else if (wacom->touch_input) {
 		dev_dbg(wacom->touch_input->dev.parent,
 			"%s: received report #%d\n", __func__, data[0]);
 
-	switch (len) {
-	case WACOM_PKGLEN_TPC1FG:
-		return wacom_tpc_single_touch(wacom, len);
-
-	case WACOM_PKGLEN_TPC2FG:
-		return wacom_tpc_mt_touch(wacom);
-
-	case WACOM_PKGLEN_PENABLED:
-		return wacom_tpc_pen(wacom);
-
-	default:
-		switch (data[0]) {
-		case WACOM_REPORT_TPC1FG:
-		case WACOM_REPORT_TPCHID:
-		case WACOM_REPORT_TPCST:
-		case WACOM_REPORT_TPC1FGE:
+		switch (len) {
+		case WACOM_PKGLEN_TPC1FG:
 			return wacom_tpc_single_touch(wacom, len);
 
-		case WACOM_REPORT_TPCMT:
-		case WACOM_REPORT_TPCMT2:
-			return wacom_mt_touch(wacom);
+		case WACOM_PKGLEN_TPC2FG:
+			return wacom_tpc_mt_touch(wacom);
 
-		case WACOM_REPORT_PENABLED:
-			return wacom_tpc_pen(wacom);
+		default:
+			switch (data[0]) {
+			case WACOM_REPORT_TPC1FG:
+			case WACOM_REPORT_TPCHID:
+			case WACOM_REPORT_TPCST:
+			case WACOM_REPORT_TPC1FGE:
+				return wacom_tpc_single_touch(wacom, len);
+
+			case WACOM_REPORT_TPCMT:
+			case WACOM_REPORT_TPCMT2:
+				return wacom_mt_touch(wacom);
+
+			}
 		}
 	}
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/hid-wacom-have-wacom_tpc_irq-guard-against-possible-null-dereference.patch