Linux kernel (drivers/vfio): Vfio deleted the device before removing its debugfs tree, so debugfs files stay visible

Impact

Vfio deleted the device before removing its debugfs tree, so debugfs files stay visible while the devres-allocated state behind them has already been released. Anything that opens those files during the unregister window - which lasts as long as userspace still holds references to the device - reads through a stale inode private pointer into freed memory.

Who can reach it

Needs host root or whatever principal can read /sys/kernel/debug/vfio, and needs the read to land inside the unregister window of a device that a tenant is still holding open. Not tenant-reachable in a normal container (debugfs is not mounted there); the realistic trigger is host monitoring or debugging tooling that walks vfio debugfs while devices are being torn down.

What to do

Update to a stable kernel carrying commits 6cc60b41 / a53109ff. Interim: do not mount debugfs on production tenant nodes, or keep monitoring agents off /sys/kernel/debug/vfio while devices are unbinding.

References