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Mon, 23 Feb 2026 14:38:52 -0800 (PST) Received: from localhost ([2a03:2880:25ff:44::]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-64c7a39bdecsm3726462d50.22.2026.02.23.14.38.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Feb 2026 14:38:52 -0800 (PST) From: Bobby Eshleman Subject: [PATCH net v3 0/3] vsock: add write-once semantics to child_ns_mode Date: Mon, 23 Feb 2026 14:38:31 -0800 Message-Id: <20260223-vsock-ns-write-once-v3-0-c0cde6959923@meta.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-B4-Tracking: v=1; b=H4sIAOjWnGkC/33NTQ7CIBBA4auQWXcM0B+hK+9hXCCdWmIEAwQ1T e9uwqoL4/ol31shUXSUYGQrRCouueBhZG3DwC7G3wjdBCMDyeXApThiScHe0Sd8RZcJg7eESrX dNKiOuJHQMHhGmt27qmfwlOHSMFhcyiF+6qmImv6iRaBAI+Zry2eptNGnB2VzsOFRuSL3hPpNS OQoNHW251PPtdkR27Z9AQT30fz9AAAA X-Change-ID: 20260217-vsock-ns-write-once-8834d684e0a2 To: Stefano Garzarella , "David S. 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, kuniyu@google.com, ncardwell@google.com, 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 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/20260218-vsock-ns-write-once-v2-0-19e4c50d509a@meta.com 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 | 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