In the Linux kernel, the following vulnerability has been resolved:

PCI: Fix pci_slot_trylock() error handling

Commit a4e772898f8b ("PCI: Add missing bridge lock to pci_bus_lock()")
delegates the bridge device's pci_dev_trylock() to pci_bus_trylock() in
pci_slot_trylock(), but it forgets to remove the corresponding
pci_dev_unlock() when pci_bus_trylock() fails.

Before a4e772898f8b, the code did:

  if (!pci_dev_trylock(dev)) /* <- lock bridge device */
    goto unlock;
  if (dev->subordinate) {
    if (!pci_bus_trylock(dev->subordinate)) {
      pci_dev_unlock(dev);   /* <- unlock bridge device */
      goto unlock;
    }
  }

After a4e772898f8b the bridge-device lock is no longer taken, but the
pci_dev_unlock(dev) on the failure path was left in place, leading to the
bug.

This yields one of two errors:

  1. A warning that the lock is being unlocked when no one holds it.
  2. An incorrect unlock of a lock that belongs to another thread.

Fix it by removing the now-redundant pci_dev_unlock(dev) on the failure
path.

[Same patch later posted by Keith at
https://patch.msgid.link/20260116184150.3013258-1-kbusch@meta.com]