Affected: Linux

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

netfilter: revalidate bridge ports

ebt_redirect_tg() dereferences br_port_get_rcu() return without a NULL check, causing a kernel panic when the bridge port has been removed between the original hook invocation and an NFQUEUE reinject.

A mere NULL check isn't sufficient, however. As sashiko review points out userspace can not only remove the port from the bridge, it could also place the device in a different virtual device, e.g. macvlan.

If this happens, we must drop the packet, there is no way for us to reinject it into the bridge path.

Switch to _upper API, we don't need the bridge port structure. Also, this fix keeps another bug intact:

Both nfnetlink_log and nfnetlink_queue use CONFIG_BRIDGE_NETFILTER too aggressive, which prevents certain logging features when queueing in bridge family: NETFILTER_FAMILY_BRIDGE can be enabled while the old CONFIG_BRIDGE_NETFILTER cruft is off.

Fixes tag is a common ancestor, this was always broken.