CVE-2026-89950

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

batman-adv: mcast: linearize skbuff for packet generation

batadv_mcast_forw_packet() and batadv_mcast_forw_scrape() is not only called (indirectly) by the unsharing+linearizing batadv_recv_mcast_packet() handler. When it is called (indirectly) by batadv_mcast_forw_mcsend() then it will be unshared but not linearized. The SKB_LINEAR_ASSERT() can therefore cause a fatal BUG().

The linearization should happen during the expansion of the head because the scrape function can be hit already during the initial batadv_mcast_forw_mode() selection code:

• batadv_interface_tx
• batadv_mcast_forw_mode
• batadv_mcast_forw_mode_by_count()
• batadv_mcast_forw_push() -> calls batadv_mcast_forw_expand_head() before everything else
• batadv_mcast_forw_push_tvlvs()
• batadv_mcast_forw_push_dests()
• batadv_mcast_forw_push_adjust_padding()
• batadv_mcast_forw_scrape()