CVE-2026-45840

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

openvswitch: cap upcall PID array size and pre-size vport replies

The vport netlink reply helpers allocate a fixed-size skb with

nlmsg_new(NLMSG_DEFAULT_SIZE, ...) but serialize the full upcall PID

array via ovs_vport_get_upcall_portids(). Since

ovs_vport_set_upcall_portids() accepts any non-zero multiple of

sizeof(u32) with no upper bound, a CAP_NET_ADMIN user can install a PID

array large enough to overflow the reply buffer, causing nla_put() to

fail with -EMSGSIZE and hitting BUG_ON(err < 0). On systems with

unprivileged user namespaces enabled (e.g., Ubuntu default), this is

reachable via unshare -Urn since OVS vport mutation operations use

GENL_UNS_ADMIN_PERM.

kernel BUG at net/openvswitch/datapath.c:2414!

Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI

CPU: 1 UID: 0 PID: 65 Comm: poc Not tainted 7.0.0-rc7-00195-geb216e422044 #1

RIP: 0010:ovs_vport_cmd_set+0x34c/0x400

Call Trace:

<TASK>

genl_family_rcv_msg_doit (net/netlink/genetlink.c:1116)

genl_rcv_msg (net/netlink/genetlink.c:1194)

netlink_rcv_skb (net/netlink/af_netlink.c:2550)

genl_rcv (net/netlink/genetlink.c:1219)

netlink_unicast (net/netlink/af_netlink.c:1344)

netlink_sendmsg (net/netlink/af_netlink.c:1894)

__sys_sendto (net/socket.c:2206)

__x64_sys_sendto (net/socket.c:2209)

do_syscall_64 (arch/x86/entry/syscall_64.c:63)

entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)

</TASK>

Kernel panic - not syncing: Fatal exception

Reject attempts to set more PIDs than nr_cpu_ids in

ovs_vport_set_upcall_portids(), and pre-compute the worst-case reply

size in ovs_vport_cmd_msg_size() based on that bound, similar to the

existing ovs_dp_cmd_msg_size(). nr_cpu_ids matches the cap already

used by the per-CPU dispatch configuration on the datapath side

(ovs_dp_cmd_fill_info() serialises at most nr_cpu_ids PIDs), so the

two sides stay consistent.