Overview

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

i3c: master: Fix recursive locking during device registration

i3c_master_register_new_i3c_devs() registers newly discovered devices while holding i3c_bus_normaluse_lock(), a down_read(). device_register() can immediately probe the device, and probe callbacks typically invoke I3C helpers that take i3c_bus_normaluse_lock() again, leading to a recursive acquisition of the same rwsem. rwsems do not support recursive read locking and can deadlock when a writer is waiting. See the "Recursive read locks" section of Documentation/locking/lockdep-design.rst.

For example, with Intel LPSS I3C, LOCKDEP generates a WARNING like:

echo intel-lpss-i3c.0 > /sys/bus/platform/drivers/mipi-i3c-hci/unbind

echo intel-lpss-i3c.0 > /sys/bus/platform/drivers/mipi-i3c-hci/bind

WARNING: possible recursive locking detected kworker/5:1/94 is trying to acquire lock: ffff88811c810d78 (&i3cbus->lock){++++}-{4:4}, at: i3c_device_match_id+0x45/0x370 but task is already holding lock: ffff88811c810d78 (&i3cbus->lock){++++}-{4:4}, at: i3c_master_reg_work_fn+0x21/0x5f0

Fix this by separating device creation from device registration. Populate desc->dev under the maintenance lock, collect the devices that still need registration into a local list, then release the lock before calling device_register(). Finally retake the lock and clean up any devices that failed to register.

Use the maintenance lock rather than the normal-use lock while adding device objects. A write-side maintenance lock prevents readers from observing a partially initialized desc->dev during initial device population, or desc->dev disappearing if registration fails.

The local list requires a list node, so add a list node member to struct i3c_device.

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.