Patch "PCI: Do not allocate more buses than available in parent" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

PCI: Do not allocate more buses than available in parent

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
pci-do-not-allocate-more-buses-than-available-in-parent.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Mika Westerberg <[email protected]>
Date: Fri, 13 Oct 2017 21:35:43 +0300
Subject: PCI: Do not allocate more buses than available in parent

From: Mika Westerberg <[email protected]>

[ Upstream commit a20c7f36bd3d20d245616ae223bb9d05dfb6f050 ]

One can ask more buses to be reserved for hotplug bridges by passing pci=hpbussize=N in the kernel command line. If the parent bus does not have enough bus space available we incorrectly create child bus with the requested number of subordinate buses.

In the example below hpbussize is set to one more than we have available buses in the root port:

pci 0000:07:00.0: [8086:1578] type 01 class 0x060400
pci 0000:07:00.0: scanning [bus 00-00] behind bridge, pass 0
pci 0000:07:00.0: bridge configuration invalid ([bus 00-00]), reconfiguring
pci 0000:07:00.0: scanning [bus 00-00] behind bridge, pass 1
pci_bus 0000:08: busn_res: can not insert [bus 08-ff] under [bus 07-3f] (conflicts with (null) [bus 07-3f]) pci_bus 0000:08: scanning bus
...
pci_bus 0000:0a: bus scan returning with max=40
pci_bus 0000:0a: busn_res: [bus 0a-ff] end is updated to 40
pci_bus 0000:0a: [bus 0a-40] partially hidden behind bridge 0000:07 [bus 07-3f]
pci_bus 0000:08: bus scan returning with max=40
pci_bus 0000:08: busn_res: [bus 08-ff] end is updated to 40

Instead of allowing this, limit the subordinate number to be less than or equal the maximum subordinate number allocated for the parent bus (if it has any).

---
 drivers/pci/probe.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

@@ -1076,7 +1076,8 @@ int pci_scan_bridge(struct pci_bus *bus,
 			child = pci_add_new_bus(bus, dev, max+1);
 			if (!child)
 				goto out;
-			pci_bus_insert_busn_res(child, max+1, 0xff);
+			pci_bus_insert_busn_res(child, max+1,
+						bus->busn_res.end);
 		}
 		max++;
 		buses = (buses & 0xff000000)

@@ -2433,6 +2434,10 @@ unsigned int pci_scan_child_bus(struct p
 	if (bus->self && bus->self->is_hotplug_bridge && pci_hotplug_bus_size) {
 		if (max - bus->busn_res.start < pci_hotplug_bus_size - 1)
 			max = bus->busn_res.start + pci_hotplug_bus_size - 1;
+
+		/* Do not allocate more buses than we have room left */
+		if (max > bus->busn_res.end)
+			max = bus->busn_res.end;
 	}
 
 	/*

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/thunderbolt-tb-fix-use-after-free-in-tb_activate_pcie_devices.patch queue-4.14/pci-do-not-allocate-more-buses-than-available-in-parent.patch