PCI: Prevent out of bounds access in numa_node override

63692df103e9 ("PCI: Allow numa_node override via sysfs") didn't check that
the numa node provided by userspace is valid.  Passing a node number too
high would attempt to access invalid memory and trigger a kernel panic.

Fixes: 63692df103e9 ("PCI: Allow numa_node override via sysfs")
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: stable@vger.kernel.org	# v3.19+

drivers/pci/pci-sysfs.c

@@ -216,7 +216,7 @@ static ssize_t numa_node_store(struct device *dev,
 	if (ret)
 		return ret;
 
-	if (!node_online(node))
+	if (node >= MAX_NUMNODES || !node_online(node))
 		return -EINVAL;
 
 	add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);