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Message-Id: <20240620042915.2173-1-ian.ray@gehealthcare.com>
Date: Thu, 20 Jun 2024 07:29:15 +0300
From: Ian Ray <ian.ray@...ealthcare.com>
To: Linus Walleij <linus.walleij@...aro.org>,
Bartosz Golaszewski <brgl@...ev.pl>
Cc: Ian Ray <ian.ray@...ealthcare.com>, linux-gpio@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH] gpio: pca953x: fix pca953x_irq_bus_sync_unlock race
Ensure that `i2c_lock' is held when setting interrupt latch and mask in
pca953x_irq_bus_sync_unlock() in order to avoid races.
The other (non-probe) call site pca953x_gpio_set_multiple() ensures the
lock is held before calling pca953x_write_regs().
The problem occurred when a request raced against irq_bus_sync_unlock()
approximately once per thousand reboots on an i.MX8MP based system.
* Normal case
0-0022: write register AI|3a {03,02,00,00,01} Input latch P0
0-0022: write register AI|49 {fc,fd,ff,ff,fe} Interrupt mask P0
0-0022: write register AI|08 {ff,00,00,00,00} Output P3
0-0022: write register AI|12 {fc,00,00,00,00} Config P3
* Race case
0-0022: write register AI|08 {ff,00,00,00,00} Output P3
0-0022: write register AI|08 {03,02,00,00,01} *** Wrong register ***
0-0022: write register AI|12 {fc,00,00,00,00} Config P3
0-0022: write register AI|49 {fc,fd,ff,ff,fe} Interrupt mask P0
Signed-off-by: Ian Ray <ian.ray@...ealthcare.com>
---
drivers/gpio/gpio-pca953x.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c
index 77a2812f2974..732a6964748c 100644
--- a/drivers/gpio/gpio-pca953x.c
+++ b/drivers/gpio/gpio-pca953x.c
@@ -758,6 +758,8 @@ static void pca953x_irq_bus_sync_unlock(struct irq_data *d)
int level;
if (chip->driver_data & PCA_PCAL) {
+ guard(mutex)(&chip->i2c_lock);
+
/* Enable latch on interrupt-enabled inputs */
pca953x_write_regs(chip, PCAL953X_IN_LATCH, chip->irq_mask);
--
2.39.2
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