[PATCH AUTOSEL 4.19 016/172] PCI: Allow pci_resize_resource() for devices on root bus

[Sasha Levin]

From: Ard Biesheuvel <ardb@xxxxxxxxxx>

[ Upstream commit d09ddd8190fbdc07696bf34b548ae15aa1816714 ]

When resizing a BAR, pci_reassign_bridge_resources() is invoked to bring
the bridge windows of parent bridges in line with the new BAR assignment.

This assumes the device whose BAR is being resized lives on a subordinate
bus, but this is not necessarily the case. A device may live on the root
bus, in which case dev->bus->self is NULL, and passing a NULL pci_dev
pointer to pci_reassign_bridge_resources() will cause it to crash.

So let's make the call to pci_reassign_bridge_resources() conditional on
whether dev->bus->self is non-NULL in the first place.

Fixes: 8bb705e3e79d84e7 ("PCI: Add pci_resize_resource() for resizing BARs")
Link: https://lore.kernel.org/r/20200421162256.26887-1-ardb@xxxxxxxxxx
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Reviewed-by: Christian KÃnig <christian.koenig@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/pci/setup-res.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/setup-res.c b/drivers/pci/setup-res.c
index d8ca40a97693..d21fa04fa44d 100644
--- a/drivers/pci/setup-res.c
+++ b/drivers/pci/setup-res.c
@@ -439,10 +439,11 @@ int pci_resize_resource(struct pci_dev *dev, int resno, int size)
 	res->end = res->start + pci_rebar_size_to_bytes(size) - 1;
 
 	/* Check if the new config works by trying to assign everything. */
-	ret = pci_reassign_bridge_resources(dev->bus->self, res->flags);
-	if (ret)
-		goto error_resize;
-
+	if (dev->bus->self) {
+		ret = pci_reassign_bridge_resources(dev->bus->self, res->flags);
+		if (ret)
+			goto error_resize;
+	}
 	return 0;
 
 error_resize:
-- 
2.25.1