diff mbox series

[v2,4/5] Input: goodix - Fix race on driver unbind

Message ID 20220131143539.109142-4-hdegoede@redhat.com (mailing list archive)
State Accepted
Commit 65de58c2a5b4bbe8ee1a42a5ee5b88163efa9855
Headers show
Series [v2,1/5] Input: Set EV_ABS in dev->evbit even if input_alloc_absinfo() fails | expand

Commit Message

Hans de Goede Jan. 31, 2022, 2:35 p.m. UTC
Because there is no way to detect if the touchscreen has pen support,
the driver is allocating and registering the input_pen input_dev on
receiving the first pen event.

But this means that the input_dev gets allocated after the request_irq()
call which means that the devm framework will free it before disabling
the irq, leaving a window where the irq handler may run and reference the
free-ed input_dev.

To fix this move the allocation of the input_pen input_dev to before
the request_irq() call, while still only registering it on the first pen
event so that the driver does not advertise pen capability on touchscreens
without it (most goodix touchscreens do not have pen support).

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v2:
- Only try input_register_device(ts->input_pen) once
- Bail early if input_register_device(ts->input_pen) failed
---
 drivers/input/touchscreen/goodix.c | 35 +++++++++++++++++++-----------
 drivers/input/touchscreen/goodix.h |  1 +
 2 files changed, 23 insertions(+), 13 deletions(-)

Comments

Dmitry Torokhov March 1, 2022, 7:04 a.m. UTC | #1
On Mon, Jan 31, 2022 at 03:35:38PM +0100, Hans de Goede wrote:
> Because there is no way to detect if the touchscreen has pen support,
> the driver is allocating and registering the input_pen input_dev on
> receiving the first pen event.
> 
> But this means that the input_dev gets allocated after the request_irq()
> call which means that the devm framework will free it before disabling
> the irq, leaving a window where the irq handler may run and reference the
> free-ed input_dev.
> 
> To fix this move the allocation of the input_pen input_dev to before
> the request_irq() call, while still only registering it on the first pen
> event so that the driver does not advertise pen capability on touchscreens
> without it (most goodix touchscreens do not have pen support).
> 
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Applied, thank you.
diff mbox series

Patch

diff --git a/drivers/input/touchscreen/goodix.c b/drivers/input/touchscreen/goodix.c
index 04baf5a770f5..b055815611de 100644
--- a/drivers/input/touchscreen/goodix.c
+++ b/drivers/input/touchscreen/goodix.c
@@ -297,14 +297,14 @@  static int goodix_ts_read_input_report(struct goodix_ts_data *ts, u8 *data)
 	return -ENOMSG;
 }
 
-static struct input_dev *goodix_create_pen_input(struct goodix_ts_data *ts)
+static int goodix_create_pen_input(struct goodix_ts_data *ts)
 {
 	struct device *dev = &ts->client->dev;
 	struct input_dev *input;
 
 	input = devm_input_allocate_device(dev);
 	if (!input)
-		return NULL;
+		return -ENOMEM;
 
 	input_copy_abs(input, ABS_X, ts->input_dev, ABS_MT_POSITION_X);
 	input_copy_abs(input, ABS_Y, ts->input_dev, ABS_MT_POSITION_Y);
@@ -331,25 +331,23 @@  static struct input_dev *goodix_create_pen_input(struct goodix_ts_data *ts)
 		input->id.product = 0x1001;
 	input->id.version = ts->version;
 
-	if (input_register_device(input) != 0) {
-		input_free_device(input);
-		return NULL;
-	}
-
-	return input;
+	ts->input_pen = input;
+	return 0;
 }
 
 static void goodix_ts_report_pen_down(struct goodix_ts_data *ts, u8 *data)
 {
-	int input_x, input_y, input_w;
+	int input_x, input_y, input_w, error;
 	u8 key_value;
 
-	if (!ts->input_pen) {
-		ts->input_pen = goodix_create_pen_input(ts);
-		if (!ts->input_pen)
-			return;
+	if (!ts->pen_input_registered) {
+		error = input_register_device(ts->input_pen);
+		ts->pen_input_registered = (error == 0) ? 1 : error;
 	}
 
+	if (ts->pen_input_registered < 0)
+		return;
+
 	if (ts->contact_size == 9) {
 		input_x = get_unaligned_le16(&data[4]);
 		input_y = get_unaligned_le16(&data[6]);
@@ -1207,6 +1205,17 @@  static int goodix_configure_dev(struct goodix_ts_data *ts)
 		return error;
 	}
 
+	/*
+	 * Create the input_pen device before goodix_request_irq() calls
+	 * devm_request_threaded_irq() so that the devm framework frees
+	 * it after disabling the irq.
+	 * Unfortunately there is no way to detect if the touchscreen has pen
+	 * support, so registering the dev is delayed till the first pen event.
+	 */
+	error = goodix_create_pen_input(ts);
+	if (error)
+		return error;
+
 	ts->irq_flags = goodix_irq_flags[ts->int_trigger_type] | IRQF_ONESHOT;
 	error = goodix_request_irq(ts);
 	if (error) {
diff --git a/drivers/input/touchscreen/goodix.h b/drivers/input/touchscreen/goodix.h
index fa8602e78a64..87797cc88b32 100644
--- a/drivers/input/touchscreen/goodix.h
+++ b/drivers/input/touchscreen/goodix.h
@@ -94,6 +94,7 @@  struct goodix_ts_data {
 	u16 version;
 	bool reset_controller_at_probe;
 	bool load_cfg_from_disk;
+	int pen_input_registered;
 	struct completion firmware_loading_complete;
 	unsigned long irq_flags;
 	enum goodix_irq_pin_access_method irq_pin_access_method;