From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Wed, 25 Sep 2019 01:16:55 +0000 (+1000)
Subject: PCI: Protect pci_reassign_bridge_resources() against concurrent addition/removal
X-Git-Tag: v5.10.7~3719^2~19^2~5
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=fb794a708a71d7c6af55f04cc4ed2d5823fb8b33;p=platform%2Fkernel%2Flinux-rpi.git

PCI: Protect pci_reassign_bridge_resources() against concurrent addition/removal

pci_reassign_bridge_resources() can be called by pci_resize_resource() at
runtime, it walks the PCI tree up and down, and it isn't currently
protected against any changes or hotplug operation.

Hold the pci_bus_sem to protect it.

Link: https://lore.kernel.org/r/7339fd73ccaf58552737ab10008333fd9f7723f2.camel@kernel.crashing.org
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
---

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index e7dbe21..f1c5194 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -2066,6 +2066,8 @@ int pci_reassign_bridge_resources(struct pci_dev *bridge, unsigned long type)
 	unsigned int i;
 	int ret;
 
+	down_read(&pci_bus_sem);
+
 	/* Walk to the root hub, releasing bridge BARs when possible */
 	next = bridge;
 	do {
@@ -2100,8 +2102,10 @@ int pci_reassign_bridge_resources(struct pci_dev *bridge, unsigned long type)
 		next = bridge->bus ? bridge->bus->self : NULL;
 	} while (next);
 
-	if (list_empty(&saved))
+	if (list_empty(&saved)) {
+		up_read(&pci_bus_sem);
 		return -ENOENT;
+	}
 
 	__pci_bus_size_bridges(bridge->subordinate, &added);
 	__pci_bridge_assign_resources(bridge, &added, &failed);
@@ -2122,6 +2126,7 @@ int pci_reassign_bridge_resources(struct pci_dev *bridge, unsigned long type)
 	}
 
 	free_list(&saved);
+	up_read(&pci_bus_sem);
 	return 0;
 
 cleanup:
@@ -2150,6 +2155,7 @@ cleanup:
 		pci_setup_bridge(bridge->subordinate);
 	}
 	free_list(&saved);
+	up_read(&pci_bus_sem);
 
 	return ret;
 }