CVE-2026-72337: Bluetooth: 6lowpan: avoid untracked enable work

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

Bluetooth: 6lowpan: avoid untracked enable work

lowpanenableset() allocates a temporary work item and schedules doenableset() on systemwq, then returns to debugfs. The debugfs active operation has ended at that point, but the worker still executes module text and manipulates enable6lowpan and listenchan.

bt6lowpanexit() removes the debugfs files and immediately closes and puts listenchan. It has no pointer to the queued work item, so it cannot cancel or flush it before tearing down the state that the worker uses.

The buggy scenario involves two paths, with each column showing the order within that path:

debugfs enable write module exit 1. lowpanenableset() allocates 1. bt6lowpanexit() removes setenable work the debugfs file 2. schedulework() queues 2. bt6lowpanexit() closes doenableset() and puts listenchan 3. the write operation returns 3. module teardown can continue 4. doenableset() later runs against stale state

Run the enable state transition synchronously in lowpanenableset() instead. The simple debugfs setter can sleep, and this file already handles the 6LoWPAN control write synchronously under the same setlock. Once the setter returns, debugfs removal covers the whole operation and exit can no longer race with an untracked work item.

Validation reproduced this kernel report: BUG: KASAN: slab-use-after-free in doenableset+0x113/0x2e0 Workqueue: events doenableset [bluetooth6lowpan] The buggy address belongs to the object at ffff888109cb8000