6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Alexander Sverdlin alexander.sverdlin@siemens.com
[ Upstream commit 7351312632e831e51383f48957d47712fae791ef ]
Enable/disable seems to be racy on SMP, consider the following scenario:
CPU0 CPU1
interrupt_cnt_enable_write(true) { if (priv->enabled == enable) return 0;
if (enable) { priv->enabled = true; interrupt_cnt_enable_write(false) { if (priv->enabled == enable) return 0;
if (enable) { priv->enabled = true; enable_irq(priv->irq); } else { disable_irq(priv->irq) priv->enabled = false; } enable_irq(priv->irq); } else { disable_irq(priv->irq); priv->enabled = false; }
The above would result in priv->enabled == false, but IRQ left enabled. Protect both write (above race) and read (to propagate the value on SMP) callbacks with a mutex.
Signed-off-by: Alexander Sverdlin alexander.sverdlin@siemens.com Fixes: a55ebd47f21f ("counter: add IRQ or GPIO based counter") Acked-by: Oleksij Rempel o.rempel@pengutronix.de Link: https://lore.kernel.org/r/20250331163642.2382651-1-alexander.sverdlin@siemen... Signed-off-by: William Breathitt Gray wbg@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/counter/interrupt-cnt.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/drivers/counter/interrupt-cnt.c b/drivers/counter/interrupt-cnt.c index 229473855c5b3..bc762ba87a19b 100644 --- a/drivers/counter/interrupt-cnt.c +++ b/drivers/counter/interrupt-cnt.c @@ -3,12 +3,14 @@ * Copyright (c) 2021 Pengutronix, Oleksij Rempel kernel@pengutronix.de */
+#include <linux/cleanup.h> #include <linux/counter.h> #include <linux/gpio/consumer.h> #include <linux/interrupt.h> #include <linux/irq.h> #include <linux/mod_devicetable.h> #include <linux/module.h> +#include <linux/mutex.h> #include <linux/platform_device.h> #include <linux/types.h>
@@ -19,6 +21,7 @@ struct interrupt_cnt_priv { struct gpio_desc *gpio; int irq; bool enabled; + struct mutex lock; struct counter_signal signals; struct counter_synapse synapses; struct counter_count cnts; @@ -41,6 +44,8 @@ static int interrupt_cnt_enable_read(struct counter_device *counter, { struct interrupt_cnt_priv *priv = counter_priv(counter);
+ guard(mutex)(&priv->lock); + *enable = priv->enabled;
return 0; @@ -51,6 +56,8 @@ static int interrupt_cnt_enable_write(struct counter_device *counter, { struct interrupt_cnt_priv *priv = counter_priv(counter);
+ guard(mutex)(&priv->lock); + if (priv->enabled == enable) return 0;
@@ -227,6 +234,8 @@ static int interrupt_cnt_probe(struct platform_device *pdev) if (ret) return ret;
+ mutex_init(&priv->lock); + ret = devm_counter_add(dev, counter); if (ret < 0) return dev_err_probe(dev, ret, "Failed to add counter\n");