CVE-2026-53013
Description
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.
Summary dbcve.org
In the Linux kernel macvlan driver, the macvlan_get_size() function fails to reserve space for the IFLA_MACVLAN_BC_CUTOFF netlink attribute, while macvlan_fill_info() conditionally includes it when port->bc_cutoff != 1. This causes nla_put_s32() to fail with -EMSGSIZE when the netlink message buffer is too small, triggering a WARN_ON in rtnetlink and preventing the interface from being dumped via 'ip -d link show'.
Mitigation
Apply the kernel patch that adds nla_total_size(4) to macvlan_get_size() to properly reserve space for the IFLA_MACVLAN_BC_CUTOFF attribute, or upgrade to a kernel version containing the fix.