[PATCH v5 bpf 0/4] lwt: fix return values of BPF ops

[Yan Zhai <yan@cloudflare.com>]

lwt xmit hook does not expect positive return values in function
ip_finish_output2 and ip6_finish_output. However, BPF programs can
directly return positive statuses such like NET_XMIT_DROP, NET_RX_DROP,
and etc to the caller. Such return values would make the kernel continue
processing already freed skbs and eventually panic.

This set fixes the return values from BPF ops to unexpected continue
processing, and checks strictly on the correct continue condition for
future proof. In addition, add missing selftests for BPF_REDIRECT
and BPF_REROUTE cases for BPF-CI.

v4: https://lore.kernel.org/bpf/ZMD1sFTW8SFiex+x@debian.debian/T/ 
v3: https://lore.kernel.org/bpf/cover.1690255889.git.yan@cloudflare.com/ 
v2: https://lore.kernel.org/netdev/ZLdY6JkWRccunvu0@debian.debian/ 
v1: https://lore.kernel.org/bpf/ZLbYdpWC8zt9EJtq@debian.debian/ 

changes since v4:
 * fixed same error on BPF_REROUTE path
 * re-implemented selftests under BPF-CI requirement

changes since v3:
 * minor change in commit message and changelogs
 * tested by Jakub Sitnicki

changes since v2:
 * subject name changed
 * also covered redirect to ingress case
 * added selftests

changes since v1:
 * minor code style changes

Yan Zhai (4):
  lwt: fix return values of BPF ops
  lwt: check LWTUNNEL_XMIT_CONTINUE strictly
  selftests/bpf: add lwt_xmit tests for BPF_REDIRECT
  selftests/bpf: add lwt_xmit tests for BPF_REROUTE

 include/net/lwtunnel.h                        |   5 +-
 net/core/lwt_bpf.c                            |   7 +-
 net/ipv4/ip_output.c                          |   2 +-
 net/ipv6/ip6_output.c                         |   2 +-
 .../selftests/bpf/prog_tests/lwt_helpers.h    | 139 ++++++++
 .../selftests/bpf/prog_tests/lwt_redirect.c   | 319 ++++++++++++++++++
 .../selftests/bpf/prog_tests/lwt_reroute.c    | 256 ++++++++++++++
 .../selftests/bpf/progs/test_lwt_redirect.c   |  58 ++++
 .../selftests/bpf/progs/test_lwt_reroute.c    |  36 ++
 9 files changed, 817 insertions(+), 7 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/lwt_helpers.h
 create mode 100644 tools/testing/selftests/bpf/prog_tests/lwt_redirect.c
 create mode 100644 tools/testing/selftests/bpf/prog_tests/lwt_reroute.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_lwt_redirect.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_lwt_reroute.c

-- 
2.30.2