[PATCH] clocksource/drivers/exynos_mct: Handle DTS with higher number of interrupts

[PATCH] clocksource/drivers/exynos_mct: Handle DTS with higher number of interrupts

[Krzysztof Kozlowski]

The driver statically defines maximum number of interrupts it can
handle, however it does not respect that limit when configuring them.
When provided with a DTS with more interrupts than assumed, the driver
will overwrite static array mct_irqs leading to silent memory
corruption.

Validate the interrupts coming from DTS to avoid this.  This does not
change the fact that such DTS might not boot at all, because it is
simply incompatible, however at least some warning will be printed.

Fixes: 36ba5d527e95 ("ARM: EXYNOS: add device tree support for MCT controller driver")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
---
 drivers/clocksource/exynos_mct.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c
index 6db3d5511b0f..03782b399ea1 100644
--- a/drivers/clocksource/exynos_mct.c
+++ b/drivers/clocksource/exynos_mct.c
@@ -541,6 +541,11 @@ static int __init exynos4_timer_interrupts(struct device_node *np,
 	 * irqs are specified.
 	 */
 	nr_irqs = of_irq_count(np);
+	if (nr_irqs > ARRAY_SIZE(mct_irqs)) {
+		pr_err("exynos-mct: too many (%d) interrupts configured in DT\n",
+			nr_irqs);
+		nr_irqs = ARRAY_SIZE(mct_irqs);
+	}
 	for (i = MCT_L0_IRQ; i < nr_irqs; i++)
 		mct_irqs[i] = irq_of_parse_and_map(np, i);
 
@@ -553,11 +558,14 @@ static int __init exynos4_timer_interrupts(struct device_node *np,
 		     mct_irqs[MCT_L0_IRQ], err);
 	} else {
 		for_each_possible_cpu(cpu) {
-			int mct_irq = mct_irqs[MCT_L0_IRQ + cpu];
+			int mct_irq;
 			struct mct_clock_event_device *pcpu_mevt =
 				per_cpu_ptr(&percpu_mct_tick, cpu);
 
 			pcpu_mevt->evt.irq = -1;
+			if (MCT_L0_IRQ + cpu >= ARRAY_SIZE(mct_irqs))
+				break;
+			mct_irq = mct_irqs[MCT_L0_IRQ + cpu];
 
 			irq_set_status_flags(mct_irq, IRQ_NOAUTOEN);
 			if (request_irq(mct_irq,
-- 
2.32.0


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RE: [PATCH] clocksource/drivers/exynos_mct: Handle DTS with higher number of interrupts

[Alim Akhtar]

>-----Original Message-----
>From: Krzysztof Kozlowski [mailto:krzysztof.kozlowski@canonical.com]
>Sent: Sunday, February 20, 2022 4:08 PM
>To: Daniel Lezcano <daniel.lezcano@linaro.org>; Thomas Gleixner
><tglx@linutronix.de>; Krzysztof Kozlowski
><krzysztof.kozlowski@canonical.com>; Alim Akhtar
><alim.akhtar@samsung.com>; Thomas Abraham
><thomas.abraham@linaro.org>; Stephen Warren <swarren@nvidia.com>;
>Kukjin Kim <kgene.kim@samsung.com>; linux-kernel@vger.kernel.org; linux-
>arm-kernel@lists.infradead.org; linux-samsung-soc@vger.kernel.org
>Subject: [PATCH] clocksource/drivers/exynos_mct: Handle DTS with higher
>number of interrupts
>
>The driver statically defines maximum number of interrupts it can handle,
>however it does not respect that limit when configuring them.
>When provided with a DTS with more interrupts than assumed, the driver will
>overwrite static array mct_irqs leading to silent memory corruption.
>
>Validate the interrupts coming from DTS to avoid this.  This does not
change
>the fact that such DTS might not boot at all, because it is simply
incompatible,
>however at least some warning will be printed.
>
>Fixes: 36ba5d527e95 ("ARM: EXYNOS: add device tree support for MCT
>controller driver")
>Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
>---
Thanks, good to have this check.

Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>



> drivers/clocksource/exynos_mct.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/clocksource/exynos_mct.c
>b/drivers/clocksource/exynos_mct.c
>index 6db3d5511b0f..03782b399ea1 100644
>--- a/drivers/clocksource/exynos_mct.c
>+++ b/drivers/clocksource/exynos_mct.c
>@@ -541,6 +541,11 @@ static int __init exynos4_timer_interrupts(struct
>device_node *np,
> 	 * irqs are specified.
> 	 */
> 	nr_irqs = of_irq_count(np);
>+	if (nr_irqs > ARRAY_SIZE(mct_irqs)) {
>+		pr_err("exynos-mct: too many (%d) interrupts configured in
>DT\n",
>+			nr_irqs);
>+		nr_irqs = ARRAY_SIZE(mct_irqs);
>+	}
> 	for (i = MCT_L0_IRQ; i < nr_irqs; i++)
> 		mct_irqs[i] = irq_of_parse_and_map(np, i);
>
>@@ -553,11 +558,14 @@ static int __init exynos4_timer_interrupts(struct
>device_node *np,
> 		     mct_irqs[MCT_L0_IRQ], err);
> 	} else {
> 		for_each_possible_cpu(cpu) {
>-			int mct_irq = mct_irqs[MCT_L0_IRQ + cpu];
>+			int mct_irq;
> 			struct mct_clock_event_device *pcpu_mevt =
> 				per_cpu_ptr(&percpu_mct_tick, cpu);
>
> 			pcpu_mevt->evt.irq = -1;
>+			if (MCT_L0_IRQ + cpu >= ARRAY_SIZE(mct_irqs))
>+				break;
>+			mct_irq = mct_irqs[MCT_L0_IRQ + cpu];
>
> 			irq_set_status_flags(mct_irq, IRQ_NOAUTOEN);
> 			if (request_irq(mct_irq,
>--
>2.32.0



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