When cgroup_skb/egress triggers the MAC header is not set. On the other hand, load_bytes_relative unconditionally calls skb_mac_header which, when MC not set, returns a pointer after the tail pointer, breaking the logic even if the caller requested the NET header. Fix is to conditionally use skb_mac_header or skb_network_header depending on the requested header, -EFAULT when the header is not set. Added a test that asserts during cgroup_skb/egress request for MAC header returns -EFAULT and request for NET header succeeds. YiFei Zhu (2): net/filter: Permit reading NET in load_bytes_relative when MAC not set selftests/bpf: Add cgroup_skb/egress test for load_bytes_relative net/core/filter.c | 16 +++-- .../bpf/prog_tests/load_bytes_relative.c | 71 +++++++++++++++++++ .../selftests/bpf/progs/load_bytes_relative.c | 44 ++++++++++++ 3 files changed, 124 insertions(+), 7 deletions(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/load_bytes_relative.c create mode 100644 tools/testing/selftests/bpf/progs/load_bytes_relative.c -- 2.27.0
