CVE-2026-31688

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

driver core: enforce devicelock for drivermatch_device()

Currently, drivermatchdevice() is called from three sites. One site (__deviceattachdriver) holds devicelock(dev), but the other two (bindstore and _driverattach) do not. This inconsistency means that bus match() callbacks are not guaranteed to be called with the lock held.

Fix this by introducing drivermatchdevicelocked(), which guarantees holding the device lock using a scoped guard. Replace the unlocked calls in bindstore() and _driverattach() with this new helper. Also add a lock assertion to drivermatchdevice() to enforce this guarantee.

This consistency also fixes a known race condition. The driveroverride implementation relies on the devicelock, so the missing lock led to the use-after-free (UAF) reported in Bugzilla for buses using this field.

Stress testing the two newly locked paths for 24 hours with CONFIGPROVELOCKING and CONFIG_LOCKDEP enabled showed no UAF recurrence and no lockdep warnings.