In the Linux kernel, the following vulnerability has been resolved:
net: bridge: stop fast-leave after deleting a port group
br_multicast_leave_group() iterates mp->ports with pp = &p->next in its fast-leave path. After br_multicast_del_pg() removes p, continuing the loop advances pp through the deleted entry.
If multicast-to-unicast was enabled, the bridge can hold multiple port groups for the same port and group with different source MAC addresses. Once multicast-to-unicast is disabled, br_port_group_equal() matches those entries by port only. A fast leave can then delete one entry and continue from its stale next pointer, leaving mp->ports pointing at a deleted port group.
Fast leave only needs to remove one matching port group. Break after br_multicast_del_pg() so the loop stops before dereferencing the removed entry.
References
- https://git.kernel.org/stable/c/0309ebbc570000ea0df11c06b69798e5860c5f6f
- https://git.kernel.org/stable/c/159ad90cb929c033308bb39a2c5f8fbf393b77aa
- https://git.kernel.org/stable/c/4695430e8132420bf8de94da3eb36a6cf35fde6b
- https://git.kernel.org/stable/c/4c57056ca6aace2e9f94ae9298bf49ef6b0c95e4
- https://git.kernel.org/stable/c/a39789f211b8a4125f0c70e05b30cf715f4f187d