[PATCH net v4 0/4] Fix UDP length overflow in edge cases

[Alice Mikityanska <alice.kernel@fastmail.im>]

From: Alice Mikityanska <alice@isovalent.com>

These are fixes for rare edge cases of 16-bit UDP length field overflow
that might happen on netdevs with MTU >= 64k.

Exposed by the new WARN added to udp_set_len_short, reported by syzbot.

v4 changes: Fixed IPv6 commit message; deduplicated code in the selftest
and fixed pylint and ruff warnings.

v3: https://lore.kernel.org/netdev/20260822115717.1161782-1-alice.kernel@fastmail.im/

v3 changes: Split IPv4, IPv6 and selftest; limited the clamp to UDP
sockets to support UDP jumbograms over raw sockets; added a selftest for
raw sockets; added the kernel config check to the selftest.

v2: https://lore.kernel.org/netdev/20260813120351.2807829-1-alice.kernel@fastmail.im/

v2 changes: Restored the MTU clamp in ip6_dst_mtu_maybe_forward.

v1: https://lore.kernel.org/netdev/20260805205957.1652619-1-alice.kernel@fastmail.im/

Alice Mikityanska (4):
  net: ipv4: Fix UDP length overflow with PMTU discover and big MTU
  net: ipv6: Fix UDP length overflow with PMTU discover and big MTU
  selftests: net: Test UDP length overflow with PMTU discover and big
    MTU
  net: ipv6: Clamp to IP6_MAX_MTU in ip6_dst_mtu_maybe_forward

 include/net/ip6_route.h                      |   2 +
 net/ipv4/ip_output.c                         |   1 +
 net/ipv6/ip6_output.c                        |   2 +
 tools/testing/selftests/net/Makefile         |   1 +
 tools/testing/selftests/net/cork_fragsize.py | 140 +++++++++++++++++++
 5 files changed, 146 insertions(+)
 create mode 100755 tools/testing/selftests/net/cork_fragsize.py

-- 
2.55.0