Commit 2ac97f0f authored Apr 25, 2017 by Jason Gerecke Committed by Jiri Kosina May 05, 2017

HID: wacom: Have wacom_tpc_irq guard against possible NULL dereference



The following Smatch complaint was generated in response to commit
2a6cdbdd ("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.

Fixes: 2a6cdbdd ("HID: wacom: Introduce new 'touch_input' device")
Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Reviewed-by: Ping Cheng <ping.cheng@wacom.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

parent 7af4c727

drivers/hid/wacom_wac.c

+23 −22

Original line number	Diff line number	Diff line
		@@ -1571,10 +1571,15 @@ static int wacom_tpc_irq(struct wacom_wac *wacom, size_t len)
		{
		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]);

		@@ -1585,9 +1590,6 @@ static int wacom_tpc_irq(struct wacom_wac *wacom, size_t 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:
		@@ -1600,8 +1602,7 @@ static int wacom_tpc_irq(struct wacom_wac *wacom, size_t len)
		case WACOM_REPORT_TPCMT2:
		return wacom_mt_touch(wacom);

		case WACOM_REPORT_PENABLED:
		return wacom_tpc_pen(wacom);
		}
		}
		}

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