linux-kernel - [PATCH] gpio: pca953x: Survive spurious interrupts

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Message-Id: <20201005140217.1390851-1-maz@kernel.org>
Date:   Mon,  5 Oct 2020 15:02:17 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        kernel-team@...roid.com
Subject: [PATCH] gpio: pca953x: Survive spurious interrupts

The pca953x driver never checks the result of irq_find_mapping(),
which returns 0 when no mapping is found. When a spurious interrupt
is delivered (which can happen under obscure circumstances), the
kernel explodes as it still tries to handle the error code as
a real interrupt.

Handle this particular case and warn on spurious interrupts.

Signed-off-by: Marc Zyngier <maz@...nel.org>
---
 drivers/gpio/gpio-pca953x.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c
index fb61f2fc6ed7..c2d6121c48c9 100644
--- a/drivers/gpio/gpio-pca953x.c
+++ b/drivers/gpio/gpio-pca953x.c
@@ -824,8 +824,21 @@ static irqreturn_t pca953x_irq_handler(int irq, void *devid)
 	ret = pca953x_irq_pending(chip, pending);
 	mutex_unlock(&chip->i2c_lock);
 
-	for_each_set_bit(level, pending, gc->ngpio)
-		handle_nested_irq(irq_find_mapping(gc->irq.domain, level));
+	if (ret) {
+		ret = 0;
+
+		for_each_set_bit(level, pending, gc->ngpio) {
+			int nested_irq = irq_find_mapping(gc->irq.domain, level);
+
+			if (unlikely(nested_irq <= 0)) {
+				dev_warn_ratelimited(gc->parent, "unmapped interrupt %d\n", level);
+				continue;
+			}
+
+			handle_nested_irq(nested_irq);
+			ret = 1;
+		}
+	}
 
 	return IRQ_RETVAL(ret);
 }
-- 
2.28.0