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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Stefan Hajnoczi , Shuah Khan , Bobby Eshleman , "Michael S. Tsirkin" , Jonathan Corbet , Shuah Khan Cc: virtualization@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-doc@vger.kernel.org, Daan De Meyer X-Mailer: b4 0.14.3 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 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/20260217-vsock-ns-write-once-v1-1-a1fb30f289a9@meta.com --- 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 | 10 ++++++--- include/net/af_vsock.h | 20 +++++++++++++++--- include/net/netns/vsock.h | 9 +++++++- net/vmw_vsock/af_vsock.c | 15 +++++++++----- tools/testing/selftests/vsock/vmtest.sh | 35 +++++++++++++++----------------- 5 files changed, 58 insertions(+), 31 deletions(-) --- base-commit: ccd8e87748ad083047d6c8544c5809b7f96cc8df change-id: 20260217-vsock-ns-write-once-8834d684e0a2 Best regards, -- Bobby Eshleman