Subject: [PATCH v2 00/10] net: Introduce struct sockaddr_unspec

From: Kees Cook <[email-masked]>
Date: Tue, 14 Oct 2025 15:43:22 -0700

Hi,

The historically fixed-size struct sockaddr is part of UAPI and embedded
in many existing structures. The kernel uses struct sockaddr extensively
within the kernel to represent arbitrarily sized sockaddr structures,
which caused problems with the compiler's ability to determine object
sizes correctly. The "temporary" solution was to make sockaddr explicitly
use a flexible array, but this causes problems for embedding struct
sockaddr in structures, where once again the compiler has to guess about
the size of such objects, and causes thousands of warnings under the
coming -Wflex-array-member-not-at-end.

Switching to sockaddr_storage internally everywhere wastes a lot of memory,
so we are left with needing two changes:
- introduction of an explicitly arbitrarily sized sockaddr struct
- switch struct sockaddr back to being fixed size

Doing the latter step requires all "arbitrarily sized" uses of struct
sockaddr to be replaced with the new struct from the first step.

So, introduce the new struct and do enough conversions that we can
switch sockaddr back to a fixed-size sa_data.

Thanks!

-Kees

 v2:
  - Include BPF casts
  - Move sockaddr_unspec out of UAPI
 v1: https://lore.kernel.org/all/[email-masked]/

Kees Cook (10):
  net: Add struct sockaddr_unspec for sockaddr of unknown length
  net/l2tp: Add missing sa_family validation in
    pppol2tp_sockaddr_get_info
  net: Convert proto_ops bind() callbacks to use sockaddr_unspec
  net: Convert proto_ops connect() callbacks to use sockaddr_unspec
  net: Remove struct sockaddr from net.h
  net: Convert proto callbacks from sockaddr to sockaddr_unspec
  bpf: Convert cgroup sockaddr filters to use sockaddr_unspec
    consistently
  bpf: Convert bpf_sock_addr_kern "uaddr" to sockaddr_unspec
  bpf: Add size validation to bpf_sock_addr_set_sun_path()
  net: Convert struct sockaddr to fixed-size "sa_data[14]"

 include/linux/bpf-cgroup.h                    | 17 ++++++++------
 include/linux/filter.h                        |  2 +-
 include/linux/net.h                           |  9 ++++----
 include/linux/socket.h                        | 23 +++++++++++++++----
 include/net/inet_common.h                     | 13 +++++------
 include/net/ip.h                              |  4 ++--
 include/net/ipv6.h                            | 10 ++++----
 include/net/ipv6_stubs.h                      |  2 +-
 include/net/ping.h                            |  2 +-
 include/net/sctp/sctp.h                       |  2 +-
 include/net/sock.h                            | 14 +++++------
 include/net/tcp.h                             |  2 +-
 include/net/udp.h                             |  2 +-
 include/net/vsock_addr.h                      |  2 +-
 net/rds/rds.h                                 |  2 +-
 net/smc/smc.h                                 |  4 ++--
 .../perf/trace/beauty/include/linux/socket.h  |  5 +---
 crypto/af_alg.c                               |  2 +-
 drivers/block/drbd/drbd_receiver.c            |  6 ++---
 drivers/infiniband/hw/erdma/erdma_cm.c        |  6 ++---
 drivers/infiniband/sw/siw/siw_cm.c            |  8 +++----
 drivers/isdn/mISDN/l1oip_core.c               |  2 +-
 drivers/isdn/mISDN/socket.c                   |  4 ++--
 drivers/net/ppp/pppoe.c                       |  4 ++--
 drivers/net/ppp/pptp.c                        |  8 +++----
 drivers/net/wireless/ath/ath10k/qmi.c         |  2 +-
 drivers/net/wireless/ath/ath11k/qmi.c         |  2 +-
 drivers/net/wireless/ath/ath12k/qmi.c         |  2 +-
 drivers/nvme/host/tcp.c                       |  4 ++--
 drivers/nvme/target/tcp.c                     |  2 +-
 drivers/slimbus/qcom-ngd-ctrl.c               |  2 +-
 drivers/target/iscsi/iscsi_target_login.c     |  2 +-
 drivers/xen/pvcalls-back.c                    |  4 ++--
 fs/afs/rxrpc.c                                |  6 ++---
 fs/coredump.c                                 |  2 +-
 fs/dlm/lowcomms.c                             |  8 +++----
 fs/ocfs2/cluster/tcp.c                        |  6 ++---
 fs/smb/client/connect.c                       |  4 ++--
 fs/smb/server/transport_tcp.c                 |  4 ++--
 kernel/bpf/cgroup.c                           |  8 +++----
 net/9p/trans_fd.c                             |  8 +++----
 net/appletalk/ddp.c                           |  4 ++--
 net/atm/pvc.c                                 |  4 ++--
 net/atm/svc.c                                 |  4 ++--
 net/ax25/af_ax25.c                            |  4 ++--
 net/bluetooth/hci_sock.c                      |  2 +-
 net/bluetooth/iso.c                           |  6 ++---
 net/bluetooth/l2cap_sock.c                    |  4 ++--
 net/bluetooth/rfcomm/core.c                   |  6 ++---
 net/bluetooth/rfcomm/sock.c                   |  5 ++--
 net/bluetooth/sco.c                           |  4 ++--
 net/caif/caif_socket.c                        |  2 +-
 net/can/bcm.c                                 |  2 +-
 net/can/isotp.c                               |  2 +-
 net/can/j1939/socket.c                        |  4 ++--
 net/can/raw.c                                 |  2 +-
 net/ceph/messenger.c                          |  2 +-
 net/core/dev.c                                |  2 +-
 net/core/dev_ioctl.c                          |  2 +-
 net/core/filter.c                             | 13 ++++++++---
 net/core/sock.c                               |  6 ++---
 net/ieee802154/socket.c                       | 12 +++++-----
 net/ipv4/af_inet.c                            | 16 ++++++-------
 net/ipv4/arp.c                                |  2 +-
 net/ipv4/datagram.c                           |  4 ++--
 net/ipv4/ping.c                               |  8 +++----
 net/ipv4/raw.c                                |  3 ++-
 net/ipv4/tcp.c                                |  2 +-
 net/ipv4/tcp_ipv4.c                           |  4 ++--
 net/ipv4/udp.c                                |  6 +++--
 net/ipv4/udp_tunnel_core.c                    |  4 ++--
 net/ipv6/af_inet6.c                           |  6 ++---
 net/ipv6/datagram.c                           |  8 +++----
 net/ipv6/ip6_udp_tunnel.c                     |  4 ++--
 net/ipv6/ping.c                               |  2 +-
 net/ipv6/raw.c                                |  3 ++-
 net/ipv6/tcp_ipv6.c                           |  6 ++---
 net/ipv6/udp.c                                |  5 ++--
 net/iucv/af_iucv.c                            |  6 ++---
 net/l2tp/l2tp_core.c                          |  8 +++----
 net/l2tp/l2tp_ip.c                            |  6 +++--
 net/l2tp/l2tp_ip6.c                           |  5 ++--
 net/l2tp/l2tp_ppp.c                           |  9 +++++++-
 net/llc/af_llc.c                              |  4 ++--
 net/mctp/af_mctp.c                            |  4 ++--
 net/mctp/test/route-test.c                    |  2 +-
 net/mctp/test/utils.c                         |  5 ++--
 net/mptcp/pm_kernel.c                         |  4 ++--
 net/mptcp/protocol.c                          |  5 ++--
 net/mptcp/subflow.c                           |  4 ++--
 net/netfilter/ipvs/ip_vs_sync.c               |  6 ++---
 net/netlink/af_netlink.c                      |  4 ++--
 net/netrom/af_netrom.c                        |  6 ++---
 net/nfc/llcp_sock.c                           |  6 ++---
 net/nfc/rawsock.c                             |  2 +-
 net/packet/af_packet.c                        | 15 ++++++------
 net/phonet/pep.c                              |  3 ++-
 net/phonet/socket.c                           | 10 ++++----
 net/qrtr/af_qrtr.c                            |  4 ++--
 net/qrtr/ns.c                                 |  2 +-
 net/rds/af_rds.c                              |  2 +-
 net/rds/bind.c                                |  2 +-
 net/rds/tcp_connect.c                         |  4 ++--
 net/rds/tcp_listen.c                          |  2 +-
 net/rose/af_rose.c                            |  4 ++--
 net/rxrpc/af_rxrpc.c                          |  4 ++--
 net/rxrpc/rxperf.c                            |  2 +-
 net/sctp/socket.c                             | 13 ++++++-----
 net/smc/af_smc.c                              |  6 ++---
 net/socket.c                                  | 14 +++++------
 net/sunrpc/clnt.c                             |  6 ++---
 net/sunrpc/svcsock.c                          |  2 +-
 net/sunrpc/xprtsock.c                         |  9 ++++----
 net/tipc/socket.c                             |  6 ++---
 net/unix/af_unix.c                            | 12 +++++-----
 net/vmw_vsock/af_vsock.c                      |  6 ++---
 net/vmw_vsock/vsock_addr.c                    |  2 +-
 net/x25/af_x25.c                              |  4 ++--
 net/xdp/xsk.c                                 |  2 +-
 119 files changed, 330 insertions(+), 288 deletions(-)

-- 
2.34.1