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gpio: timberdale: Fix potential deadlock on &tgpio->lock

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As timbgpio_irq_enable()/timbgpio_irq_disable() callback could be
executed under irq context, it could introduce double locks on
&tgpio->lock if it preempts other execution units requiring
the same locks.

timbgpio_gpio_set()
--> timbgpio_update_bit()
--> spin_lock(&tgpio->lock)
<interrupt>
   --> timbgpio_irq_disable()
   --> spin_lock_irqsave(&tgpio->lock)

This flaw was found by an experimental static analysis tool I am
developing for irq-related deadlock.

To prevent the potential deadlock, the patch uses spin_lock_irqsave()
on &tgpio->lock inside timbgpio_gpio_set() to prevent the possible
deadlock scenario.

Signed-off-by: Chengfeng Ye <dg573847474@gmail.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
This commit is contained in:
Chengfeng Ye 2023-09-26 10:29:14 +00:00 committed by Bartosz Golaszewski
parent 6465e260f4
commit 9e8bc2dda5
1 changed files with 3 additions and 2 deletions
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5
drivers/gpio/gpio-timberdale.c
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@ -43,9 +43,10 @@ static int timbgpio_update_bit(struct gpio_chip *gpio, unsigned index,
unsigned offset, bool enabled)
{
struct timbgpio *tgpio = gpiochip_get_data(gpio);
unsigned long flags;
u32 reg;
spin_lock(&tgpio->lock);
spin_lock_irqsave(&tgpio->lock, flags);
reg = ioread32(tgpio->membase + offset);
if (enabled)
@ -54,7 +55,7 @@ static int timbgpio_update_bit(struct gpio_chip *gpio, unsigned index,
reg &= ~(1 << index);
iowrite32(reg, tgpio->membase + offset);
spin_unlock(&tgpio->lock);
spin_unlock_irqrestore(&tgpio->lock, flags);
return 0;
}