Two administrator processes may race when setting child_ns_mode: one sets it to "local" and creates a namespace, but another changes it to "global" in between. The first process ends up with a namespace in the wrong mode. Make child_ns_mode write-once so that a namespace manager can set it once, check the value, and be guaranteed it won't change before creating its namespaces. Writing a different value after the first write returns -EBUSY.
One patch for the implementation, one for docs, and one for tests. --- Changes in v3: - Simplify code be reverting approach of using only a single variable to represent both lock state and child_ns_mode state. Instead, use child_ns_mode and child_ns_mode_locked. - Update documentation to clarify the value-dependent behavior of child_ns_mode writes (that is, same value is ok, different value gets -EBUSY). - fixed some line length > 80 checkpatch issues in vmtest.sh - Link to v2: https://lore.kernel.org/r/[email protected] Changes in v2: - break docs, tests, and implementation into separate patches - clarify commit message - only use child_ns_mode, do not add additional child_ns_mode_locked variable - add documentation to Documentation/ - Link to v1: https://lore.kernel.org/r/[email protected] --- Bobby Eshleman (3): selftests/vsock: change tests to respect write-once child ns mode vsock: lock down child_ns_mode as write-once vsock: document write-once behavior of the child_ns_mode sysctl Documentation/admin-guide/sysctl/net.rst | 3 +++ include/net/af_vsock.h | 13 ++++++++-- include/net/netns/vsock.h | 3 +++ net/vmw_vsock/af_vsock.c | 15 ++++++++---- tools/testing/selftests/vsock/vmtest.sh | 41 ++++++++++++++++---------------- 5 files changed, 48 insertions(+), 27 deletions(-) --- base-commit: ccd8e87748ad083047d6c8544c5809b7f96cc8df change-id: 20260217-vsock-ns-write-once-8834d684e0a2 Best regards, -- Bobby Eshleman <[email protected]>
