The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 1204e35bedf4e5015cda559ed8c84789a6dae24e Mon Sep 17 00:00:00 2001
From: Lukas Wunner lukas@wunner.de Date: Thu, 19 Jul 2018 17:27:34 -0500 Subject: [PATCH] PCI: pciehp: Fix unprotected list iteration in IRQ handler
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") Signed-off-by: Lukas Wunner lukas@wunner.de Signed-off-by: Bjorn Helgaas bhelgaas@google.com Cc: stable@vger.kernel.org
diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c index 84b3d421c083..aff191b4552c 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) wake_up(&ctrl->queue); }
- 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 */