batman-adv: fix panic during interface removal

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: batman-adv: fix panic during interface removal Reference counting is used to ensure that batadv_hardif_neigh_node and batadv_hard_iface are not freed before/during batadv_v_elp_throughput_metric_update work is finished. But there isn't a guarantee that the hard if will remain associated with a soft interface up until the work is finished. This fixes a crash triggered by reboot that looks like this: Call trace: batadv_v_mesh_free+0xd0/0x4dc [batman_adv] batadv_v_elp_throughput_metric_update+0x1c/0xa4 process_one_work+0x178/0x398 worker_thread+0x2e8/0x4d0 kthread+0xd8/0xdc ret_from_fork+0x10/0x20 (the batadv_v_mesh_free call is misleading, and does not actually happen) I was able to make the issue happen more reliably by changing hardif_neigh->bat_v.metric_work work to be delayed work. This allowed me to track down and confirm the fix. [sven@narfation.org: prevent entering batadv_v_elp_get_throughput without soft_iface]

References

• https://git.kernel.org/stable/c/167422a07096a6006599067c8b55884064fa0b72
• https://git.kernel.org/stable/c/ce3f1545bf8fa28bd05ec113679e8e6cd23af577
• https://git.kernel.org/stable/c/f0a16c6c79768180333f3e41ce63f32730e3c3af
• https://git.kernel.org/stable/c/7eb5dd201695645af071592a50026eb780081a72
• https://git.kernel.org/stable/c/072b2787321903287a126c148e8db87dd7ef96fe
• https://git.kernel.org/stable/c/2c3fb7df4cc6d043f70d4a8a10f8b915bbfb75e7
• https://git.kernel.org/stable/c/522b1596ea19e327853804da2de60aeb9c5d6f42
• https://git.kernel.org/stable/c/ccb7276a6d26d6f8416e315b43b45e15ee7f29e2