High [CVE-2026-64218] fix report_work leak on backbone_gw purge

In the Linux kernel, the following vulnerability has been resolved: batman-adv: bla: fix report_work leak on backbone_gw purge batadv_bla_purge_backbone_gw() removes stale backbone gateway entries, but fails to properly handle their associated report_work: - If report_work is running, the purge must wait for it to finish before freeing the backbone_gw, otherwise the worker may access freed memory (e.g. bat_priv). - If report_work is pending, the purge must cancel it and release the reference held for that pending work item.

The previous implementation called hlist_for_each_entry_safe() inside a spin_lock_bh() section, but cancel_work_sync() may sleep and therefore cannot be called from within a spinlock-protected region.

Restructure the loop to handle one entry per spinlock critical section: acquire the lock, find the next entry to purge, remove it from the hash list, then release the lock before calling cancel_work_sync() and dropping the hash_entry reference. Repeat until no more entries require purging.

This vulnerability is rated as Important because the race condition can result in kernel use-after-free memory corruption, potentially enabling local privilege escalation or complete system compromise. In typical Red Hat Enterprise Linux environments, the B.A.T.M.A.N.

Advanced mesh networking module is neither loaded nor enabled by default.