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:
- A warning that the lock is being unlocked when no one holds it.
- 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/[email protected]]