CVE-2026-89950

Summary

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()

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/a9603e0a7cb5e0cddc6b23af153cf7daafc5c55e
• https://git.kernel.org/stable/c/c32e5e25c41201c8c3b796a4ab2c45103187091e
• https://git.kernel.org/stable/c/2879177539e3ece483a8e5406970373698e9a6c5
• https://git.kernel.org/stable/c/6a30a59e2660afd03c975f1b8eae6a2301161197

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