CVE-2026-23209

Description

In the Linux kernel, the following vulnerability has been resolved:macvlan: fix error recovery in macvlan_common_newlink()valis provided a nice repro to crash the kernel:ip link add p1 type veth peer p2ip link set address 00:00:00:00:00:20 dev p1ip link set up dev p1ip link set up dev p2ip link add mv0 link p2 type macvlan mode sourceip link add invalid% link p2 type macvlan mode source macaddr add 00:00:00:00:00:20ping -c1 -I p1 1.2.3.4He also gave a very detailed analysis:The issue is triggered when a new macvlan link is created withMACVLAN_MODE_SOURCE mode and MACVLAN_MACADDR_ADD (orMACVLAN_MACADDR_SET) parameter, lower device already has a macvlanport and register_netdevice() called from macvlan_common_newlink()fails (e.g. because of the invalid link name).In this case macvlan_hash_add_source is called frommacvlan_change_sources() / macvlan_common_newlink():This adds a reference to vlan to the ports vlan_source_hash usingmacvlan_source_entry.vlan is a pointer to the priv data of the link that is being created.When register_netdevice() fails, the error is returned frommacvlan_newlink() to rtnl_newlink_create(): if (ops->newlink) err = ops->newlink(dev, ¶ms, extack); else err = register_netdevice(dev); if (err < 0) { free_netdev(dev); goto out; }and free_netdev() is called, causing a kvfree() on the structnet_device that is still referenced in the source entry attached tothe lower devices macvlan port.Now all packets sent on the macvlan port with a matching source macaddress will trigger a use-after-free in macvlan_forward_source().With all that, my fix is to make sure we call macvlan_flush_sources()regardless of @create value whenever goto destroy_macvlan_port;path is taken.Many thanks to valis for following up on this issue.

Risk Information

Associated Vulnerability

Patch Details

References

https://nvd.nist.gov/vuln/detail/CVE-2023-1234
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-1234