Linux kernel (drivers/pci/hotplug): The hotplug driver disables MSI/MSI-X during slot unregistration after the MSI data

Impact

The hotplug driver disables MSI/MSI-X during slot unregistration after the MSI data structure has already been freed and NULLed on the disable path. The NULL dereference crashes the host kernel, so hot-unplugging a PCIe switch or bridge takes the whole node down rather than removing one device.

Who can reach it

Triggered by disabling or hot-unplugging a PCIe switch/bridge from the host bridge - an operator sysfs action or a physical removal, neither requiring tenant privilege. PowerNV only (pnv_php on OpenPOWER); inert on x86 and ARM GPU nodes. Relevant only if IBM POWER hosts are in the fleet.

What to do

Update to a kernel carrying the fix (fixed_in lists only very old branches; use the stable commits below against your running branch). Interim on PowerNV: drain the node before removing bridges or switches.

References