[PATCH 2/5] HID: wacom: check the input devices in the legacy irq handlers

[Jinmo Yang <jinmo44.yang@gmail.com>]

wacom_penpartner_irq(), wacom_pl_irq(), wacom_ptu_irq(),
wacom_dtu_irq(), wacom_dtus_irq() and wacom_graphire_irq() take
pen_input, and the latter two also take pad_input, without checking
either.

As described in "HID: wacom: check the input device in the shared
report helpers", a partial interface leaves one or two of the three
input devices NULL on a fully successful probe, and wacom_wac_irq()
still dispatches to these handlers. Seven locations fault, each
reproduced on linux-next 20260925 (x86_64, KASAN) from one /dev/uhid
device plus a single UHID_INPUT2 write:

  wacom_wac.c:137   wacom_penpartner_irq    pen_input
  wacom_wac.c:227   wacom_pl_irq            pen_input
  wacom_wac.c:244   wacom_ptu_irq           pen_input
  wacom_wac.c:303   wacom_dtus_irq          pad_input
  wacom_wac.c:326   wacom_dtus_irq          pen_input
  wacom_wac.c:391   wacom_graphire_irq      pen_input
  wacom_wac.c:444   wacom_graphire_irq      pad_input

for example, with vendor 0x056a product 0x0030 (PL) and report id 2:

  BUG: KASAN: null-ptr-deref in input_event+0x44/0xb0
  Read of size 8 at addr 0000000000000028
   wacom_wac_irq+0x2b27/0xb3f0
   wacom_raw_event+0x68f/0xb60
   __hid_input_report+0x398/0x4d0
   uhid_char_write+0xa99/0xfc0

Check each pointer where it is taken. wacom_dtus_irq() and
wacom_graphire_irq() serve both pen and pad reports, so the checks are
placed per branch rather than at function entry: an interface that has
a pad but no pen must keep delivering pad events.

wacom_dtu_irq() gets a check too. Its only dereference is in a
dev_dbg(), so it does not fault with CONFIG_DYNAMIC_DEBUG=n, but it is
unconditional in the source.

Fixes: 2a6cdbdd4cc0 ("HID: wacom: Introduce new 'touch_input' device")
Fixes: 862cf5535c0c ("HID: wacom: Introduce a new WACOM_DEVICETYPE_PAD device_type")
Cc: stable@vger.kernel.org
Signed-off-by: Jinmo Yang <jinmo44.yang@gmail.com>
---
 drivers/hid/wacom_wac.c | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c
index 177a1e09fd05..794c2865064a 100644
--- a/drivers/hid/wacom_wac.c
+++ b/drivers/hid/wacom_wac.c
@@ -128,6 +128,9 @@ static int wacom_penpartner_irq(struct wacom_wac *wacom)
 	unsigned char *data = wacom->data;
 	struct input_dev *input = wacom->pen_input;
 
+	if (!input)
+		return 0;
+
 	switch (data[0]) {
 	case 1:
 		if (data[5] & 0x80) {
@@ -174,6 +177,9 @@ static int wacom_pl_irq(struct wacom_wac *wacom)
 	struct input_dev *input = wacom->pen_input;
 	int prox, pressure;
 
+	if (!input)
+		return 0;
+
 	if (data[0] != WACOM_REPORT_PENABLED) {
 		dev_dbg(input->dev.parent,
 			"%s: received unknown report #%d\n", __func__, data[0]);
@@ -233,6 +239,9 @@ static int wacom_ptu_irq(struct wacom_wac *wacom)
 	unsigned char *data = wacom->data;
 	struct input_dev *input = wacom->pen_input;
 
+	if (!input)
+		return 0;
+
 	if (data[0] != WACOM_REPORT_PENABLED) {
 		dev_dbg(input->dev.parent,
 			"%s: received unknown report #%d\n", __func__, data[0]);
@@ -263,6 +272,9 @@ static int wacom_dtu_irq(struct wacom_wac *wacom)
 	struct input_dev *input = wacom->pen_input;
 	int prox = data[1] & 0x20;
 
+	if (!input)
+		return 0;
+
 	dev_dbg(input->dev.parent,
 		"%s: received report #%d", __func__, data[0]);
 
@@ -299,6 +311,8 @@ static int wacom_dtus_irq(struct wacom_wac *wacom)
 		return 0;
 	} else if (data[0] == WACOM_REPORT_DTUSPAD) {
 		input = wacom->pad_input;
+		if (!input)
+			return 0;
 		input_report_key(input, BTN_0, (data[1] & 0x01));
 		input_report_key(input, BTN_1, (data[1] & 0x02));
 		input_report_key(input, BTN_2, (data[1] & 0x04));
@@ -307,6 +321,9 @@ static int wacom_dtus_irq(struct wacom_wac *wacom)
 				 data[1] & 0x0f ? PAD_DEVICE_ID : 0);
 		return 1;
 	} else {
+		if (!input)
+			return 0;
+
 		prox = data[1] & 0x80;
 		if (prox) {
 			switch ((data[1] >> 3) & 3) {
@@ -363,7 +380,7 @@ static int wacom_graphire_irq(struct wacom_wac *wacom)
 	}
 
 	prox = data[1] & 0x80;
-	if (prox || wacom->id[0]) {
+	if (input && (prox || wacom->id[0])) {
 		if (prox) {
 			switch ((data[1] >> 5) & 3) {
 
@@ -438,7 +455,7 @@ static int wacom_graphire_irq(struct wacom_wac *wacom)
 	switch (features->type) {
 	case WACOM_G4:
 		prox = data[7] & 0xf8;
-		if (prox || wacom->id[1]) {
+		if (pad_input && (prox || wacom->id[1])) {
 			wacom->id[1] = PAD_DEVICE_ID;
 			input_report_key(pad_input, BTN_BACK, (data[7] & 0x40));
 			input_report_key(pad_input, BTN_FORWARD, (data[7] & 0x80));
@@ -453,7 +470,7 @@ static int wacom_graphire_irq(struct wacom_wac *wacom)
 
 	case WACOM_MO:
 		prox = (data[7] & 0xf8) || data[8];
-		if (prox || wacom->id[1]) {
+		if (pad_input && (prox || wacom->id[1])) {
 			wacom->id[1] = PAD_DEVICE_ID;
 			input_report_key(pad_input, BTN_BACK, (data[7] & 0x08));
 			input_report_key(pad_input, BTN_LEFT, (data[7] & 0x20));
@@ -468,7 +485,7 @@ static int wacom_graphire_irq(struct wacom_wac *wacom)
 		break;
 	case GRAPHIRE_BT:
 		prox = data[7] & 0x03;
-		if (prox || wacom->id[1]) {
+		if (pad_input && (prox || wacom->id[1])) {
 			wacom->id[1] = PAD_DEVICE_ID;
 			input_report_key(pad_input, BTN_0, (data[7] & 0x02));
 			input_report_key(pad_input, BTN_1, (data[7] & 0x01));
-- 
2.53.0