ACPI: PCI: IRQ: Fix INTx GSIs signedness

In ACPI Global System Interrupts (GSIs) are described using a 32-bit
value.

ACPI/PCI legacy interrupts (INTx) parsing code treats GSIs as 'int',
which poses issues if the GSI interrupt value is a 32-bit value with the
MSB set (as required in some interrupt configurations - eg ARM64 GICv5
systems) because acpi_pci_link_allocate_irq() treats a negative gsi
return value as a failed GSI allocation (and acpi_irq_get_penalty()
would trigger an out-of-bounds array dereference if the 'irq' param is
a negative value).

Fix ACPI/PCI legacy INTx parsing by converting variables representing
GSIs from 'int' to 'u32' bringing the code in line with the ACPI
specification and fixing the current parsing issue.

Signed-off-by: Lorenzo Pieralisi <[e-mail]>
Reviewed-by: Bjorn Helgaas <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/acpi/pci_irq.c

···
 	 * the IRQ value, which is hardwired to specific interrupt inputs on
 	 * the interrupt controller.
 	 */
-	pr_debug("%04x:%02x:%02x[%c] -> %s[%d]\n",
+	pr_debug("%04x:%02x:%02x[%c] -> %s[%u]\n",
 		 entry->id.segment, entry->id.bus, entry->id.device,
 		 pin_name(entry->pin), prt->source, entry->index);
 
···
 int acpi_pci_irq_enable(struct pci_dev *dev)
 {
 	struct acpi_prt_entry *entry;
-	int gsi;
+	u32 gsi;
 	u8 pin;
 	int triggering = ACPI_LEVEL_SENSITIVE;
 	/*
···
 			return 0;
 	}
 
+	rc = -ENODEV;
+
 	if (entry) {
 		if (entry->link)
-			gsi = acpi_pci_link_allocate_irq(entry->link,
+			rc = acpi_pci_link_allocate_irq(entry->link,
 							 entry->index,
 							 &triggering, &polarity,
-							 &link);
-		else
+							 &link, &gsi);
+		else {
 			gsi = entry->index;
-	} else
-		gsi = -1;
+			rc = 0;
+		}
+	}
 
-	if (gsi < 0) {
+	if (rc < 0) {
 		/*
 		 * No IRQ known to the ACPI subsystem - maybe the BIOS /
 		 * driver reported one, then use it. Exit in any case.

drivers/acpi/pci_link.c

···
 	/* >IRQ15 */
 };
 
-static int acpi_irq_pci_sharing_penalty(int irq)
+static int acpi_irq_pci_sharing_penalty(u32 irq)
 {
 	struct acpi_pci_link *link;
 	int penalty = 0;
···
 	return penalty;
 }
 
-static int acpi_irq_get_penalty(int irq)
+static int acpi_irq_get_penalty(u32 irq)
 {
 	int penalty = 0;
 
···
 static int acpi_pci_link_allocate(struct acpi_pci_link *link)
 {
 	acpi_handle handle = link->device->handle;
-	int irq;
+	u32 irq;
 	int i;
 
 	if (link->irq.initialized) {
···
 	return 0;
 }
 
-/*
- * acpi_pci_link_allocate_irq
- * success: return IRQ >= 0
- * failure: return -1
+/**
+ * acpi_pci_link_allocate_irq(): Retrieve a link device GSI
+ *
+ * @handle: Handle for the link device
+ * @index: GSI index
+ * @triggering: pointer to store the GSI trigger
+ * @polarity: pointer to store GSI polarity
+ * @name: pointer to store link device name
+ * @gsi: pointer to store GSI number
+ *
+ * Returns:
+ *	0 on success with @triggering, @polarity, @name, @gsi initialized.
+ *	-ENODEV on failure
  */
 int acpi_pci_link_allocate_irq(acpi_handle handle, int index, int *triggering,
-			       int *polarity, char **name)
+			       int *polarity, char **name, u32 *gsi)
 {
 	struct acpi_device *device = acpi_fetch_acpi_dev(handle);
 	struct acpi_pci_link *link;
 
 	if (!device) {
 		acpi_handle_err(handle, "Invalid link device\n");
-		return -1;
+		return -ENODEV;
 	}
 
 	link = acpi_driver_data(device);
 	if (!link) {
 		acpi_handle_err(handle, "Invalid link context\n");
-		return -1;
+		return -ENODEV;
 	}
 
 	/* TBD: Support multiple index (IRQ) entries per Link Device */
 	if (index) {
 		acpi_handle_err(handle, "Invalid index %d\n", index);
-		return -1;
+		return -ENODEV;
 	}
 
 	mutex_lock(&acpi_link_lock);
 	if (acpi_pci_link_allocate(link)) {
 		mutex_unlock(&acpi_link_lock);
-		return -1;
+		return -ENODEV;
 	}
 
 	if (!link->irq.active) {
 		mutex_unlock(&acpi_link_lock);
 		acpi_handle_err(handle, "Link active IRQ is 0!\n");
-		return -1;
+		return -ENODEV;
 	}
 	link->refcnt++;
 	mutex_unlock(&acpi_link_lock);
···
 	if (name)
 		*name = acpi_device_bid(link->device);
 	acpi_handle_debug(handle, "Link is referenced\n");
-	return link->irq.active;
+	*gsi = link->irq.active;
+
+	return 0;
 }
 
 /*

drivers/xen/acpi.c

···
 						  int *trigger_out,
 						  int *polarity_out)
 {
-	int gsi;
+	u32 gsi;
 	u8 pin;
 	struct acpi_prt_entry *entry;
 	int trigger = ACPI_LEVEL_SENSITIVE;
-	int polarity = acpi_irq_model == ACPI_IRQ_MODEL_GIC ?
+	int ret, polarity = acpi_irq_model == ACPI_IRQ_MODEL_GIC ?
 				      ACPI_ACTIVE_HIGH : ACPI_ACTIVE_LOW;
 
 	if (!dev || !gsi_out || !trigger_out || !polarity_out)
···
 
 	entry = acpi_pci_irq_lookup(dev, pin);
 	if (entry) {
+		ret = 0;
 		if (entry->link)
-			gsi = acpi_pci_link_allocate_irq(entry->link,
+			ret = acpi_pci_link_allocate_irq(entry->link,
 							 entry->index,
 							 &trigger, &polarity,
-							 NULL);
+							 NULL, &gsi);
 		else
 			gsi = entry->index;
 	} else
-		gsi = -1;
+		ret = -ENODEV;
 
-	if (gsi < 0)
+	if (ret < 0)
 		return -EINVAL;
 
 	*gsi_out = gsi;

include/acpi/acpi_drivers.h

···
 
 int acpi_irq_penalty_init(void);
 int acpi_pci_link_allocate_irq(acpi_handle handle, int index, int *triggering,
-			       int *polarity, char **name);
+			       int *polarity, char **name, u32 *gsi);
 int acpi_pci_link_free_irq(acpi_handle handle);
 
 /* ACPI PCI Device Binding */