PCI: Release resource invalidated by coalescing

commit e54223275ba1bc6f704a6bab015fcd2ae4f72572 upstream.

When contiguous windows are coalesced by pci_register_host_bridge(), the
second resource is expanded to include the first, and the first is
invalidated and consequently not added to the bus. However, it remains in
the resource hierarchy.  For example, these windows:

  fec00000-fec7ffff : PCI Bus 0000:00
  fec80000-fecbffff : PCI Bus 0000:00

are coalesced into this, where the first resource remains in the tree with
start/end zeroed out:

  00000000-00000000 : PCI Bus 0000:00
  fec00000-fecbffff : PCI Bus 0000:00

In some cases (e.g. the Xen scratch region), this causes future calls to
allocate_resource() to choose an inappropriate location which the caller
cannot handle.

Fix by releasing the zeroed-out resource and removing it from the resource
hierarchy.

[bhelgaas: commit log]
Fixes: 7c3855c423b1 ("PCI: Coalesce host bridge contiguous apertures")
Link: https://lore.kernel.org/r/20230525153248.712779-1-ross.lagerwall@citrix.com
Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: stable@vger.kernel.org	# v5.16+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 6f9f72a08cd745d6ad6428e11fbb6c82fd192971..773715992cf0d56469c9e385b79d87b2e5cdb00e 100644 (file)
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -999,8 +999,10 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
        resource_list_for_each_entry_safe(window, n, &resources) {
                offset = window->offset;
                res = window->res;
-               if (!res->flags && !res->start && !res->end)
+               if (!res->flags && !res->start && !res->end) {
+                       release_resource(res);
                        continue;
+               }
 
                list_move_tail(&window->node, &bridge->windows);