x86/PCI: Fix PCI IRQ routing table memory leak

BugLink: https://bugs.launchpad.net/bugs/1836666

[ Upstream commit ea094d53 ]

In pcibios_irq_init(), the PCI IRQ routing table 'pirq_table' is first
found through pirq_find_routing_table().  If the table is not found and
CONFIG_PCI_BIOS is defined, the table is then allocated in
pcibios_get_irq_routing_table() using kmalloc().  Later, if the I/O APIC is
used, this table is actually not used.  In that case, the allocated table
is not freed, which is a memory leak.

Free the allocated table if it is not used.
Signed-off-by: Wenwen Wang <wang6495@umn.edu>
[bhelgaas: added Ingo's reviewed-by, since the only change since v1 was to
use the irq_routing_table local variable name he suggested]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

arch/x86/pci/irq.c

@@ -1117,6 +1117,8 @@ static struct dmi_system_id __initdata pciirq_dmi_table[] = {
 
 void __init pcibios_irq_init(void)
 {
+	struct irq_routing_table *rtable = NULL;
+
 	DBG(KERN_DEBUG "PCI: IRQ init\n");
 
 	if (raw_pci_ops == NULL)
@@ -1127,8 +1129,10 @@ void __init pcibios_irq_init(void)
 	pirq_table = pirq_find_routing_table();
 
 #ifdef CONFIG_PCI_BIOS
-	if (!pirq_table && (pci_probe & PCI_BIOS_IRQ_SCAN))
+	if (!pirq_table && (pci_probe & PCI_BIOS_IRQ_SCAN)) {
 		pirq_table = pcibios_get_irq_routing_table();
+		rtable = pirq_table;
+	}
 #endif
 	if (pirq_table) {
 		pirq_peer_trick();
@@ -1143,8 +1147,10 @@ void __init pcibios_irq_init(void)
 		 * If we're using the I/O APIC, avoid using the PCI IRQ
 		 * routing table
 		 */
-		if (io_apic_assign_pci_irqs)
+		if (io_apic_assign_pci_irqs) {
+			kfree(rtable);
 			pirq_table = NULL;
+		}
 	}
 
 	x86_init.pci.fixup_irqs();