In the Linux kernel, the following vulnerability has been resolved: net: nfc: fix deadlock between nfc_unregister_device and rfkill_fop_write A deadlock can occur between nfc_unregister_device() and rfkill_fop_write() due to lock order…

Overview

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

net: nfc: fix deadlock between nfc_unregister_device and rfkill_fop_write

A deadlock can occur between nfc_unregister_device() and rfkill_fop_write() due to lock ordering inversion between device_lock and rfkill_global_mutex.

The problematic lock order is:

Thread A (rfkill_fop_write): rfkill_fop_write() mutex_lock(&rfkill_global_mutex) rfkill_set_block() nfc_rfkill_set_block() nfc_dev_down() device_lock(&dev->dev) <- waits for device_lock

Thread B (nfc_unregister_device): nfc_unregister_device() device_lock(&dev->dev) rfkill_unregister() mutex_lock(&rfkill_global_mutex) <- waits for rfkill_global_mutex

This creates a classic ABBA deadlock scenario.

Fix this by moving rfkill_unregister() and rfkill_destroy() outside the device_lock critical section. Store the rfkill pointer in a local variable before releasing the lock, then call rfkill_unregister() after releasing device_lock.

This change is safe because rfkill_fop_write() holds rfkill_global_mutex while calling the rfkill callbacks, and rfkill_unregister() also acquires rfkill_global_mutex before cleanup. Therefore, rfkill_unregister() will wait for any ongoing callback to complete before proceeding, and device_del() is only called after rfkill_unregister() returns, preventing any use-after-free.

The similar lock ordering in nfc_register_device() (device_lock -> rfkill_global_mutex via rfkill_register) is safe because during registration the device is not yet in rfkill_list, so no concurrent rfkill operations can occur on this device.

Affected

• linux_kernel >= 4.4.293, < 4.5
• linux_kernel >= 4.9.291, < 4.10
• linux_kernel >= 4.14.256, < 4.15
• linux_kernel >= 4.19.218, < 4.20
• linux_kernel >= 5.4.162, < 5.5
• linux_kernel >= 5.10.82, < 5.10.248
• linux_kernel >= 5.15.5, < 5.15.198
• linux_kernel >= 5.16.1, < 6.1.160
• linux_kernel >= 6.2, < 6.6.120
• linux_kernel >= 6.7, < 6.12.64
• linux_kernel >= 6.13, < 6.18.4
• linux_kernel = 5.16
• linux_kernel = 6.19

Remediation

Upgrade past the affected range:

• linux_kernel 6.18.4