[PATCH bpf-next v2 0/2] bpf/flow_dissector: add mode to enforce global BPF flow dissector

[Stanislav Fomichev <sdf@google.com>]

While having a per-net-ns flow dissector programs is convenient for
testing, security-wise it's better to have only one vetted global
flow dissector implementation.

Let's have a convention that when BPF flow dissector is installed
in the root namespace, child namespaces can't override it.

The intended use-case is to attach global BPF flow dissector
early from the init scripts/systemd. Attaching global dissector
is prohibited if some non-root namespace already has flow dissector
attached. Also, attaching to non-root namespace is prohibited
when there is flow dissector attached to the root namespace.

v2:
* EPERM -> EEXIST (Song Liu)
* Make sure we don't have dissector attached to non-root namespaces
  when attaching the global one (Andrii Nakryiko)

Cc: Petar Penkov <ppenkov@google.com>

Stanislav Fomichev (2):
  bpf/flow_dissector: add mode to enforce global BPF flow dissector
  selftests/bpf: add test for BPF flow dissector in the root namespace

 Documentation/bpf/prog_flow_dissector.rst     |  3 ++
 net/core/flow_dissector.c                     | 42 ++++++++++++++--
 .../selftests/bpf/test_flow_dissector.sh      | 48 ++++++++++++++++---
 3 files changed, 83 insertions(+), 10 deletions(-)

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2.23.0.581.g78d2f28ef7-goog