CVE-2026-53013

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

macvlan: fix macvlan_get_size() not reserving space for IFLA_MACVLAN_BC_CUTOFF

macvlan_get_size() does not account for IFLA_MACVLAN_BC_CUTOFF, but

macvlan_fill_info() conditionally includes it when port->bc_cutoff != 1.

This causes nla_put_s32() to fail with -EMSGSIZE when the netlink skb

runs out of space, triggering a WARN_ON in rtnetlink and preventing the

interface from being dumped.

The bug can be reproduced with:

ip link add macvlan0 link eth0 type macvlan mode bridge

ip link set macvlan0 type macvlan bc_cutoff 0

ip -d link show macvlan0 # fails with -EMSGSIZE

The bc_cutoff feature was added in commit 954d1fa1ac93 ("macvlan: Add

netlink attribute for broadcast cutoff"), which added the nla_put_s32()

call in macvlan_fill_info() but missed adding the corresponding

nla_total_size(4) in macvlan_get_size(). A follow-up commit

55cef78c244d ("macvlan: add forgotten nla_policy for

IFLA_MACVLAN_BC_CUTOFF") fixed the missing nla_policy entry but still

did not fix the size calculation.