linux-kernel - [PATCH] Input: gpio-keys - fix crash when disabliing GPIO-less buttons

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Message-ID: <YG1DFFgojSVfdpaz@google.com>
Date:   Tue, 6 Apr 2021 22:28:52 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Paul Cercueil <paul@...pouillou.net>, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] Input: gpio-keys - fix crash when disabliing GPIO-less
 buttons

My brain-damaged adjustments to Paul's patch caused crashes in
gpio_keys_disable_button() when driver is used in GPIO-less (i.e.
purely interrupt-driven) setups, because I mixed together debounce and
release timers when they are in fact separate:

Unable to handle kernel NULL pointer dereference at virtual address 0000000c
...
PC is at hrtimer_active+0xc/0x98
LR is at hrtimer_try_to_cancel+0x24/0x140
...
[<c01c43b8>] (hrtimer_active) from [<c01c50f4>] (hrtimer_try_to_cancel+0x24/0x140)
[<c01c50f4>] (hrtimer_try_to_cancel) from [<c01c5224>] (hrtimer_cancel+0x14/0x4c)
[<c01c5224>] (hrtimer_cancel) from [<bf1cae24>] (gpio_keys_attr_store_helper+0x1b8/0x1d8 [gpio_keys])
[<bf1cae24>] (gpio_keys_attr_store_helper [gpio_keys]) from [<bf1cae80>] (gpio_keys_store_disabled_keys+0x18/0x24 [gpio_keys])
[<bf1cae80>] (gpio_keys_store_disabled_keys [gpio_keys]) from [<c038ec7c>] (kernfs_fop_write_iter+0x10c/0x1cc)
[<c038ec7c>] (kernfs_fop_write_iter) from [<c02df858>] (vfs_write+0x2ac/0x404)
[<c02df858>] (vfs_write) from [<c02dfaf4>] (ksys_write+0x64/0xdc)
[<c02dfaf4>] (ksys_write) from [<c0100080>] (ret_fast_syscall+0x0/0x58)

Let's fix it up.

Fixes: c9efb0ba281e ("Input: gpio-keys - use hrtimer for software debounce, if possible")
Reported-by: Tony Lindgren <tony@...mide.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
---

Tony, could you please try this patch and see if it fixes the crash you
observed?

Thanks!

 drivers/input/keyboard/gpio_keys.c | 30 +++++++++++++-----------------
 1 file changed, 13 insertions(+), 17 deletions(-)

diff --git a/drivers/input/keyboard/gpio_keys.c b/drivers/input/keyboard/gpio_keys.c
index fe8fc76ee22e..8dbf1e69c90a 100644
--- a/drivers/input/keyboard/gpio_keys.c
+++ b/drivers/input/keyboard/gpio_keys.c
@@ -125,6 +125,18 @@ static const unsigned long *get_bm_events_by_type(struct input_dev *dev,
 	return (type == EV_KEY) ? dev->keybit : dev->swbit;
 }

+static void gpio_keys_quiesce_key(void *data)
+{
+	struct gpio_button_data *bdata = data;
+
+	if (!bdata->gpiod)
+		hrtimer_cancel(&bdata->release_timer);
+	if (bdata->debounce_use_hrtimer)
+		hrtimer_cancel(&bdata->debounce_timer);
+	else
+		cancel_delayed_work_sync(&bdata->work);
+}
+
 /**
  * gpio_keys_disable_button() - disables given GPIO button
  * @bdata: button data for button to be disabled
@@ -145,12 +157,7 @@ static void gpio_keys_disable_button(struct gpio_button_data *bdata)
 		 * Disable IRQ and associated timer/work structure.
 		 */
 		disable_irq(bdata->irq);
-
-		if (bdata->debounce_use_hrtimer)
-			hrtimer_cancel(&bdata->release_timer);
-		else
-			cancel_delayed_work_sync(&bdata->work);
-
+		gpio_keys_quiesce_key(bdata);
 		bdata->disabled = true;
 	}
 }
@@ -492,16 +499,6 @@ static irqreturn_t gpio_keys_irq_isr(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }

-static void gpio_keys_quiesce_key(void *data)
-{
-	struct gpio_button_data *bdata = data;
-
-	if (bdata->debounce_use_hrtimer)
-		hrtimer_cancel(&bdata->debounce_timer);
-	else
-		cancel_delayed_work_sync(&bdata->work);
-}
-
 static int gpio_keys_setup_key(struct platform_device *pdev,
 				struct input_dev *input,
 				struct gpio_keys_drvdata *ddata,
@@ -635,7 +632,6 @@ static int gpio_keys_setup_key(struct platform_device *pdev,
 		}

 		bdata->release_delay = button->debounce_interval;
-		bdata->debounce_use_hrtimer = true;
 		hrtimer_init(&bdata->release_timer,
 			     CLOCK_REALTIME, HRTIMER_MODE_REL_HARD);
 		bdata->release_timer.function = gpio_keys_irq_timer;
-- 
2.31.0.208.g409f899ff0-goog

-- 
Dmitry