Medium [CVE-2026-74331] Fix recursive lock in device_cache_fw_images

In the Linux kernel, the following vulnerability has been resolved: firmware_loader: Fix recursive lock in device_cache_fw_images() A recursive locking deadlock can occur in the firmware loader's power management notification handler. During system suspend or hibernation preparation, fw_pm_notify() calls device_cache_fw_images().

This function acquires fw_lock to set the firmware cache state to FW_LOADER_START_CACHE and then iterates over all devices using dpm_for_each_dev() while still holding the lock. For each device, dev_cache_fw_image() schedules asynchronous work to cache the firmware.

If memory allocation for the async work entry fails (e.g., in out-of-memory conditions), async_schedule_node_domain() falls back to executing the work function synchronously in the current thread. The synchronous execution path (__async_dev_cache_fw_image() -> cache_firmware() -> request_firmware() -> assign_fw()) attempts to acquire fw_lock again.

Since the current thread already holds fw_lock, this results in a recursive locking deadlock. Fix this by releasing fw_lock immediately after updating the cache state and before calling dpm_for_each_dev().

The lock is only needed to protect the state update. Concurrent firmware requests will correctly see the FW_LOADER_START_CACHE state and use the piggyback mechanism, which is independently protected by its own fwc->name_lock.