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>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Link: https://lore.kernel.org/r/20220220103815.135380-1-krzysztof.kozlowski@canonical.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c
index 6db3d5511b0ffa9cc388aaf405d2c1039649eb1c..03782b399ea1a4c8f8b9f31aacb0c0b032c56af4 100644 (file)
--- 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,