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[82.53.134.58]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-483b8791a0esm73910215e9.0.2026.02.24.07.10.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 Feb 2026 07:10:34 -0800 (PST) Date: Tue, 24 Feb 2026 16:10:31 +0100 From: Stefano Garzarella To: Bobby Eshleman Cc: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Stefan Hajnoczi , Shuah Khan , Bobby Eshleman , "Michael S. Tsirkin" , Jonathan Corbet , Shuah Khan , 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 Subject: Re: [PATCH net v3 2/3] vsock: lock down child_ns_mode as write-once Message-ID: References: <20260223-vsock-ns-write-once-v3-0-c0cde6959923@meta.com> <20260223-vsock-ns-write-once-v3-2-c0cde6959923@meta.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: On Mon, Feb 23, 2026 at 04:24:07PM -0800, Bobby Eshleman wrote: >On Mon, Feb 23, 2026 at 02:38:33PM -0800, Bobby Eshleman wrote: >> From: Bobby Eshleman >> >> Two administrator processes may race when setting child_ns_mode as one >> process sets child_ns_mode to "local" and then creates a namespace, but >> another process changes child_ns_mode to "global" between the write and >> the namespace creation. The first process ends up with a namespace in >> "global" mode instead of "local". While this can be detected after the >> fact by reading ns_mode and retrying, it is fragile and error-prone. >> >> Make child_ns_mode write-once so that a namespace manager can set it >> once and be sure it won't change. Writing a different value after the >> first write returns -EBUSY. This applies to all namespaces, including >> init_net, where an init process can write "local" to lock all future >> namespaces into local mode. >> >> Fixes: eafb64f40ca4 ("vsock: add netns to vsock core") >> Suggested-by: Daan De Meyer >> Suggested-by: Stefano Garzarella >> Co-developed-by: Stefano Garzarella >> Signed-off-by: Stefano Garzarella > >Stefano, I wasn't sure if you wanted the Co-developed-by and S-o-b on >this iteration, but I added it just in case. Please let me know, if that >wasn't what you intended. It's fine, thanks for that! Stefano