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[04/32] PCI: pciehp: Fix unprotected list iteration in IRQ handler

Message ID 3cfa5672468ed406e6e00937eef1b5cff8b0cdb5.1529173804.git.lukas@wunner.de
State Accepted
Delegated to: Bjorn Helgaas
Headers show
Series Rework pciehp event handling & add runtime PM | expand

Commit Message

Lukas Wunner June 16, 2018, 7:25 p.m. UTC
Commit b440bde74f04 ("PCI: Add pci_ignore_hotplug() to ignore hotplug
events for a device") iterates over the devices on a hotplug port's
subordinate bus in pciehp's IRQ handler without acquiring pci_bus_sem.
It is thus possible for a user to cause a crash by concurrently
manipulating the device list, e.g. by disabling slot power via sysfs
on a different CPU or by initiating a remove/rescan via sysfs.

This can't be fixed by acquiring pci_bus_sem because it may sleep.
The simplest fix is to avoid the list iteration altogether and just
check the ignore_hotplug flag on the port itself.  This works because
pci_ignore_hotplug() sets the flag both on the device as well as on its
parent bridge.

We do lose the ability to print the name of the device blocking hotplug
in the debug message, but that's probably bearable.

Fixes: b440bde74f04 ("PCI: Add pci_ignore_hotplug() to ignore hotplug events for a device")
Cc: stable@vger.kernel.org
Signed-off-by: Lukas Wunner <lukas@wunner.de>
 drivers/pci/hotplug/pciehp_hpc.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)
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diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index 26b85440053e..044087e2683d 100644
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -539,8 +539,6 @@  static irqreturn_t pciehp_isr(int irq, void *dev_id)
 	struct controller *ctrl = (struct controller *)dev_id;
 	struct pci_dev *pdev = ctrl_dev(ctrl);
-	struct pci_bus *subordinate = pdev->subordinate;
-	struct pci_dev *dev;
 	struct slot *slot = ctrl->slot;
 	u16 status, events;
 	u8 present;
@@ -588,14 +586,9 @@  static irqreturn_t pciehp_isr(int irq, void *dev_id)
-	if (subordinate) {
-		list_for_each_entry(dev, &subordinate->devices, bus_list) {
-			if (dev->ignore_hotplug) {
-				ctrl_dbg(ctrl, "ignoring hotplug event %#06x (%s requested no hotplug)\n",
-					 events, pci_name(dev));
-				return IRQ_HANDLED;
-			}
-		}
+	if (pdev->ignore_hotplug) {
+		ctrl_dbg(ctrl, "ignoring hotplug event %#06x\n", events);
+		return IRQ_HANDLED;
 	/* Check Attention Button Pressed */