genirq/debugfs: Add missing sanity checks to interrupt injection

Interrupts cannot be injected when the interrupt is not activated and when
a replay is already in progress.

Fixes: 536e2e3 ("genirq/debugfs: Triggering of interrupts from userspace")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20200306130623.500019114@linutronix.de

kernel/irq/debugfs.c

@@ -206,8 +206,15 @@ static ssize_t irq_debug_write(struct file *file, const char __user *user_buf,
 		chip_bus_lock(desc);
 		raw_spin_lock_irqsave(&desc->lock, flags);
 
-		if (irq_settings_is_level(desc) || desc->istate & IRQS_NMI) {
-			/* Can't do level nor NMIs, sorry */
+		/*
+		 * Don't allow injection when the interrupt is:
+		 *  - Level or NMI type
+		 *  - not activated
+		 *  - replaying already
+		 */
+		if (irq_settings_is_level(desc) ||
+		    !irqd_is_activated(&desc->irq_data) ||
+		    (desc->istate & (IRQS_NMI | IRQS_REPLAY))) {
 			err = -EINVAL;
 		} else {
 			desc->istate |= IRQS_PENDING;