gpio: pca953x: fix pca953x_irq_bus_sync_unlock regmap lock

Locking is disabled in the regmap config as this driver uses its own
lock. This means that all calls to regmap functions (read or write) must
hold the i2c_lock. The function pca953x_irq_bus_sync_unlock() did not do
this, and it was therefore possible that multiple threads could cause an
incorrect register to be read/written.

A previous patch partly fixed this, but only protected the write to the
interrupt mask register, and not the read from the direction register.

Fixes: bfc6444b57dc ("gpio: pca953x: fix pca953x_irq_bus_sync_unlock race")
Cc: stable@vger.kernel.org
Signed-off-by: Mark Tomlinson <mark.tomlinson@alliedtelesis.co.nz>
Link: https://patch.msgid.link/20260709045116.2304246-1-mark.tomlinson@alliedtelesis.co.nz
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>

1 files changed, 14 insertions, 5 deletions

diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c
index f6b870b7b352..e03bf1b12091 100644
--- a/drivers/gpio/gpio-pca953x.c
+++ b/drivers/gpio/gpio-pca953x.c
@@ -604,20 +604,28 @@ static int pca953x_read_regs(struct pca953x_chip *chip, int reg, unsigned long *
 	return 0;
 }
 
-static int pca953x_gpio_direction_input(struct gpio_chip *gc, unsigned off)
+static int pca953x_gpio_direction_input_unlocked(struct gpio_chip *gc,
+						 unsigned int off)
 {
 	struct pca953x_chip *chip = gpiochip_get_data(gc);
 	u8 dirreg = chip->recalc_addr(chip, chip->regs->direction, off);
 	u8 bit = pca953x_get_bit_mask(chip, off);
 
-	guard(mutex)(&chip->i2c_lock);
-
 	if (PCA_CHIP_TYPE(chip->driver_data) == TCA6418_TYPE)
 		return regmap_update_bits(chip->regmap, dirreg, bit, 0);
 
 	return regmap_update_bits(chip->regmap, dirreg, bit, bit);
 }
 
+static int pca953x_gpio_direction_input(struct gpio_chip *gc, unsigned int off)
+{
+	struct pca953x_chip *chip = gpiochip_get_data(gc);
+
+	guard(mutex)(&chip->i2c_lock);
+
+	return pca953x_gpio_direction_input_unlocked(gc, off);
+}
+
 static int pca953x_gpio_direction_output(struct gpio_chip *gc,
 		unsigned off, int val)
 {
@@ -855,9 +863,10 @@ static void pca953x_irq_bus_sync_unlock(struct irq_data *d)
 	DECLARE_BITMAP(reg_direction, MAX_LINE);
 	int level;
 
+	guard(mutex)(&chip->i2c_lock);
+
 	if (chip->driver_data & PCA_PCAL) {
 		DECLARE_BITMAP(latched_inputs, MAX_LINE);
-		guard(mutex)(&chip->i2c_lock);
 
 		/* Enable latch on edge-triggered interrupt-enabled inputs */
 		bitmap_or(latched_inputs, chip->irq_trig_fall, chip->irq_trig_raise, gc->ngpio);
@@ -879,7 +888,7 @@ static void pca953x_irq_bus_sync_unlock(struct irq_data *d)
 
 	/* Look for any newly setup interrupt */
 	for_each_andnot_bit(level, irq_mask, reg_direction, gc->ngpio)
-		pca953x_gpio_direction_input(&chip->gpio_chip, level);
+		pca953x_gpio_direction_input_unlocked(&chip->gpio_chip, level);
 
 	mutex_unlock(&chip->irq_lock);
 }