From nobody Fri Apr 3 06:26:50 2026 Received: from mail-yw1-f177.google.com (mail-yw1-f177.google.com [209.85.128.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AD41437B41E for ; Mon, 23 Feb 2026 22:38:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.177 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771886336; cv=none; b=NRzCVYaOM5Q0+ttAZ75i4y3M7bxL90gf6yLpNgYUT1V4KTXQ4d46ncZwdI1vyZkCwSZLKxDhXFGBtHA8MpkiUo11qNarD7JCOQKtqY/XARyzd67ChMQlnROWyE3DCm04sBiSjQc3bWQ1FrphJ6UaQQvFy1rhdl13zuFRQRZclEU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771886336; c=relaxed/simple; bh=H9xSN+o2u3DPOyU3qSAxjvQ1NV6WYvyCbOgeBvy/A0A=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=a6JWg2RVotdPHb86s9PopuOUkLuHG9V/QTFKvcCk1bmBPCzUzoO9nk2QGRZHAyKZsDGybzeCZ4S95u5hGChoqUgMBu6+IwDTVTE4z7UlnZ+AJW7c8NARLonDMxRXjpulGtikyRZmyT6yEaX0eDTv8DaynHkO2MsDSihcLdAqNyk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=Fx1eohyf; arc=none smtp.client-ip=209.85.128.177 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Fx1eohyf" Received: by mail-yw1-f177.google.com with SMTP id 00721157ae682-79430ef54c3so42658527b3.2 for ; Mon, 23 Feb 2026 14:38:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1771886334; x=1772491134; darn=vger.kernel.org; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:from:to:cc:subject:date:message-id :reply-to; bh=M6YNbaSbY/a/RFjAEl4EW9IaCZutb07kY998isXwAsE=; b=Fx1eohyffkGHHbjY1dC1zf8vtzUj9QGwo+dO7ADM9n7bciwc6Gs3QCRY5g+VKISPfW gRrQNpKubUfNLy79WSE7xzVLcjT7FAUXv6YMMkfD2zu05cmy1TuxR/0JDfnte8stKX+x BCSKbxdhbis5kVe8HLrEEMI3jXoHZnOv1AUlm0jDDnzvOM1wdcSlYf74cj1Pc2n5EoJ6 rDnP2pR4f23rWOJSQ04z+a0DUsCnqC2voT+H7P4dQ3AClHJ8fgtUoIPL4nCS5o7pTrMe zXBSI5hiQ5yW01d0ytFJ5bF6wCcfUqJxL2J9HOltbdxKOdeYx/4pttsuKqbJholVz++/ 6T4g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1771886334; x=1772491134; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:x-gm-gg:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to; bh=M6YNbaSbY/a/RFjAEl4EW9IaCZutb07kY998isXwAsE=; b=JcGB5fn3yYQGDnowiNjwe5gmpO/PzoS4Nds0WVzdilzsgpX7F0/Dc3JfOw5RJO2J0f rFEv65kogVd0CHdmQaZ7QI4SophrvGfQRVrQHmI6AqEuSoiqc5qcPzaHXCwHXnQ0kDrd Ory56HJc7dQhNdxNGfMWpDVBV/wt9nwLSI/B3nX7CTM23KrmDOSF+3SMP8Bc4mrLST3k ooV+FTb0dHPmZytyenQqIG+6wgkEEWYUBKEcUVMZh+/sSsM8IQIEK4Lkhw6UxxoiAGwk 7px2qCDtxeCriyTU1FDQLe+Pr53YUpGTs/d5iMeJ/4/kmmzc8NlwRCMu+p2bcNeS5GRN g3JA== X-Forwarded-Encrypted: i=1; AJvYcCUrxlACKYp0xQgSLBgsTWBClAKU5ZcTQYKUfgWnx/sXUAoKNIJIlz1d5D4ktwcbFX+zvrhRfia3HaQgpWc=@vger.kernel.org X-Gm-Message-State: AOJu0YyAr0ipN/iTUBgbjucvSYQOuCkUaIimD/+TiKtB/X2wtHS9yy3H hRbn6njAyQ39xiU6aw2UztV1KDDduzoFzQaWL/0YL0sxI7o+NZP4E2oz X-Gm-Gg: ATEYQzzkSN/6YUH+tifTSLmHOLMh2oSoliovnffYSYMTpruPTptKn3o9hTPVm2sxZM0 Yse7BIbQvUQCU58bvN4auukfJueKwNV+JUvzvbfGLmNv3bwURqVBM4z9K8nBfpqbKK/yk+/aj6H gcr42RYF42adRqP9OOY8DvEm7QhUUES69ke2ZjcLh4l4rlyCiD2WshqY12xRNAVect6hj93Liof LVazJjezNWmJIf22VGApyDyb2hakux8+d3l22ZJJPj3FI66RsSOyDeO56NyDE/bFMSBsktdoAHT MZGW3XSqwikYyHVkICO0OusfIPjNS0knw24ikWCOp+UH8X75sP8zx3aOYaJmoK1Lx6yE/0Nne8P bplsQ8XtwHxVGkXYv5zzVI5UoAtx+QDO7AY+abKUFcXtZF0LNPwTDnw1tXaxP9QSfbwhOSK/q/f rjx7nuNsMCzl3lEciGCRb6 X-Received: by 2002:a05:690c:6d91:b0:794:baaa:cca7 with SMTP id 00721157ae682-79828f1e7b7mr96957847b3.20.1771886333827; Mon, 23 Feb 2026 14:38:53 -0800 (PST) Received: from localhost ([2a03:2880:25ff:5::]) by smtp.gmail.com with ESMTPSA id 00721157ae682-7982ddccc24sm37639337b3.40.2026.02.23.14.38.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Feb 2026 14:38:53 -0800 (PST) From: Bobby Eshleman Date: Mon, 23 Feb 2026 14:38:32 -0800 Subject: [PATCH net v3 1/3] selftests/vsock: change tests to respect write-once child ns mode Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260223-vsock-ns-write-once-v3-1-c0cde6959923@meta.com> References: <20260223-vsock-ns-write-once-v3-0-c0cde6959923@meta.com> In-Reply-To: <20260223-vsock-ns-write-once-v3-0-c0cde6959923@meta.com> 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 X-Mailer: b4 0.14.3 From: Bobby Eshleman The child_ns_mode sysctl parameter becomes write-once in a future patch in this series, which breaks existing tests. This patch updates the tests to respect this new policy. No additional tests are added. Add "global-parent" and "local-parent" namespaces as intermediaries to spawn namespaces in the given modes. This avoids the need to change "child_ns_mode" in the init_ns. nsenter must be used because ip netns unshares the mount namespace so nested "ip netns add" breaks exec calls from the init ns. Adds nsenter to the deps check. Reviewed-by: Stefano Garzarella Signed-off-by: Bobby Eshleman --- tools/testing/selftests/vsock/vmtest.sh | 41 +++++++++++++++++------------= ---- 1 file changed, 21 insertions(+), 20 deletions(-) diff --git a/tools/testing/selftests/vsock/vmtest.sh b/tools/testing/selfte= sts/vsock/vmtest.sh index dc8dbe74a6d0..86e338886b33 100755 --- a/tools/testing/selftests/vsock/vmtest.sh +++ b/tools/testing/selftests/vsock/vmtest.sh @@ -210,16 +210,21 @@ check_result() { } =20 add_namespaces() { - local orig_mode - orig_mode=3D$(cat /proc/sys/net/vsock/child_ns_mode) - - for mode in "${NS_MODES[@]}"; do - echo "${mode}" > /proc/sys/net/vsock/child_ns_mode - ip netns add "${mode}0" 2>/dev/null - ip netns add "${mode}1" 2>/dev/null - done - - echo "${orig_mode}" > /proc/sys/net/vsock/child_ns_mode + ip netns add "global-parent" 2>/dev/null + echo "global" | ip netns exec "global-parent" \ + tee /proc/sys/net/vsock/child_ns_mode &>/dev/null + ip netns add "local-parent" 2>/dev/null + echo "local" | ip netns exec "local-parent" \ + tee /proc/sys/net/vsock/child_ns_mode &>/dev/null + + nsenter --net=3D/var/run/netns/global-parent \ + ip netns add "global0" 2>/dev/null + nsenter --net=3D/var/run/netns/global-parent \ + ip netns add "global1" 2>/dev/null + nsenter --net=3D/var/run/netns/local-parent \ + ip netns add "local0" 2>/dev/null + nsenter --net=3D/var/run/netns/local-parent \ + ip netns add "local1" 2>/dev/null } =20 init_namespaces() { @@ -237,6 +242,8 @@ del_namespaces() { log_host "removed ns ${mode}0" log_host "removed ns ${mode}1" done + ip netns del "global-parent" &>/dev/null + ip netns del "local-parent" &>/dev/null } =20 vm_ssh() { @@ -287,7 +294,7 @@ check_args() { } =20 check_deps() { - for dep in vng ${QEMU} busybox pkill ssh ss socat; do + for dep in vng ${QEMU} busybox pkill ssh ss socat nsenter; do if [[ ! -x $(command -v "${dep}") ]]; then echo -e "skip: dependency ${dep} not found!\n" exit "${KSFT_SKIP}" @@ -1231,12 +1238,8 @@ test_ns_local_same_cid_ok() { } =20 test_ns_host_vsock_child_ns_mode_ok() { - local orig_mode - local rc - - orig_mode=3D$(cat /proc/sys/net/vsock/child_ns_mode) + local rc=3D"${KSFT_PASS}" =20 - rc=3D"${KSFT_PASS}" for mode in "${NS_MODES[@]}"; do local ns=3D"${mode}0" =20 @@ -1246,15 +1249,13 @@ test_ns_host_vsock_child_ns_mode_ok() { continue fi =20 - if ! echo "${mode}" > /proc/sys/net/vsock/child_ns_mode; then - log_host "child_ns_mode should be writable to ${mode}" + if ! echo "${mode}" | ip netns exec "${ns}" \ + tee /proc/sys/net/vsock/child_ns_mode &>/dev/null; then rc=3D"${KSFT_FAIL}" continue fi done =20 - echo "${orig_mode}" > /proc/sys/net/vsock/child_ns_mode - return "${rc}" } =20 --=20 2.47.3 From nobody Fri Apr 3 06:26:50 2026 Received: from mail-yw1-f171.google.com (mail-yw1-f171.google.com [209.85.128.171]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A4A5537BE76 for ; Mon, 23 Feb 2026 22:38:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.171 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771886338; cv=none; b=sAchP9OROTyLz+slgYYfzwW5lUePOazm3MDbtKUH9Zng/XCmtOANU/Xfl4C4PTMB3E8gUUAZBm55fbzjI2mMoYZI8mCIhMSs5JRJipgOY9ZftuzCfPbCiJK5/NNPmR88PkIdXz7iQQk27gjEmDsCAs1G19YzvJ9HUpzHyqvLOOg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771886338; c=relaxed/simple; bh=WgeYmElNUd8JWXtDscMvKbTYKQRR4nvqCMrxNQNtld4=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=Rr+rINwLWpPIMiGCaGLBGbb9nbBSf2db1sItCVbp+vby8xHITLo2DS7V7VlLRTDNh8g1D5rBd2OoEAVGi1WTdlY0Ad09YBV9KyhkMpUIy786vzKy5Mr/InRke+CU8luTe+KquOsCWLz7rP++fW+oQsf39+spyqTwEYZbk90XNtU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=jE8odhRp; arc=none smtp.client-ip=209.85.128.171 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="jE8odhRp" Received: by mail-yw1-f171.google.com with SMTP id 00721157ae682-7980ca83937so38367277b3.1 for ; Mon, 23 Feb 2026 14:38:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1771886335; x=1772491135; darn=vger.kernel.org; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:from:to:cc:subject:date:message-id :reply-to; bh=g/yCmM+X3z1/BoTwo6svOrTqbVDwyb97Jpk/MjzyWmU=; b=jE8odhRpi+A5fYcaIkttPI6rdvQvXlTeFUD7oqhwWKK6ZsCv/rkRijElk2BkBcw7ID kXl7UaVfk4gq5d3fmJ4x035+0JYeBZZTI48hPI0DhyTAoqhCFWm58tFnUxbd/SPqOy9P 3TH52LdyySAvIMZjRgh8NU6vvZIN3i+dBqOTm75rK26J1qtUnGDFYJwDV3yMGLRlHK31 5tTKoW/TAaloqxP7wX29sXv8grKlph030P7cgpHQyEIH5g1C00Eqs1Z0W70jhq0NRAL6 JFj3JCRrc9piWD6in6TC4q1bok4Y+LqAUWQAKy1e07hS1o/YAN1c+hp0EVLb799Qu4uh BDbA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1771886335; x=1772491135; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:x-gm-gg:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to; bh=g/yCmM+X3z1/BoTwo6svOrTqbVDwyb97Jpk/MjzyWmU=; b=bKmbx4cYr+gkwQRCu3Ods60LM3IbOBbPwgMvSIAnxjOXq608fMXlD6zi4tOwdychRz YhXOiDFg/0vij2poZraZmLEPXlHilHSWtHbcMM6/d/8riEhcdGzQ3Vm95w+KFQY/qUWO mxMCN/htdz1a8Pyk4NJ07kd1yJ2CDwB+oO7PhTa3v9tsT/1pXHLgoZAldKmPpXbceak5 wZLBfUho9rtnNXYywKVQcLrJ/XN/jq5pWsvRqcSYo24zAtDzNuPF9ARLdR+FnUAd+AFi 2PmrWdM4UbiLprqbpX4QcLhDZ4o10RFN7P9GHYyKpDzPEp4yWzi3Frc5SMIrDiSkFqTd hxHQ== X-Forwarded-Encrypted: i=1; AJvYcCVKEm86hmPP1wtjeCXmzp+UcSChQnfXl3xWSreqYqvgHQ+TskbbM02B8vl+g9rbOBpsiZZYgL2xoTkcJkM=@vger.kernel.org X-Gm-Message-State: AOJu0Yxg0x3zWJ/5y2Oy4eMXLGBEmqiH5hA3iUrWY4pAkaIyBKpL/+Yo vFN66ch6lvX2+YsABQ3WUfT6D8XVacRXb8t22GSulZBw4oNLWq4mhfG1 X-Gm-Gg: ATEYQzyI+HeFKapM7RaeMmqFhQq47ZOjSPa1FCQbNsE6g+uXFx0XhqaIYJqDPFf882P Gh2t5OqbQYMApBZnwFHxViJp5HMVGGA/QGt4tQbiR2LwoVMPjDo4JRa1sknjezGUTkhd9sdB7tR WCAu2BV9gBMyQRtEfEt5A3XrEpv5NqdSmMjob/HvriS2esy6D56KvqLCdXqr6emTRrjKxZDebD2 95iW2iVLewyhP7t7xPnJr6A6vYoCO7R5Eb9fFHVjpO3cfxI/XWAXwCbY6JMf5vEFY5I4Ri0I2gJ SVq/ghuAX7OkBb2Tni8kRPMaMZHb+5cj4RU2i7+7jDIp6tATi/kEfCU14sRP0zRn3Pm1HbMJJPn 70DNscwyw4PJuuToFWz3LVkADKedM0DfjN+H6vOavAbPtREi0FTJAV8uSPni8FpW3aIQb1/Qrh8 MSpDIxXW3M7k9FPPVhRr9eDC1u5wcciz7s X-Received: by 2002:a05:690c:a:b0:794:c01a:18e6 with SMTP id 00721157ae682-7982903c9aamr91568337b3.47.1771886334599; Mon, 23 Feb 2026 14:38:54 -0800 (PST) Received: from localhost ([2a03:2880:25ff:54::]) by smtp.gmail.com with ESMTPSA id 00721157ae682-7982dbdf23dsm37723417b3.21.2026.02.23.14.38.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Feb 2026 14:38:54 -0800 (PST) From: Bobby Eshleman Date: Mon, 23 Feb 2026 14:38:33 -0800 Subject: [PATCH net v3 2/3] vsock: lock down child_ns_mode as write-once Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260223-vsock-ns-write-once-v3-2-c0cde6959923@meta.com> References: <20260223-vsock-ns-write-once-v3-0-c0cde6959923@meta.com> In-Reply-To: <20260223-vsock-ns-write-once-v3-0-c0cde6959923@meta.com> 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 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 Signed-off-by: Bobby Eshleman Reviewed-by: Stefano Garzarella --- include/net/af_vsock.h | 13 +++++++++++-- include/net/netns/vsock.h | 3 +++ net/vmw_vsock/af_vsock.c | 15 ++++++++++----- 3 files changed, 24 insertions(+), 7 deletions(-) diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h index d3ff48a2fbe0..533d8e75f7bb 100644 --- a/include/net/af_vsock.h +++ b/include/net/af_vsock.h @@ -276,10 +276,19 @@ static inline bool vsock_net_mode_global(struct vsock= _sock *vsk) return vsock_net_mode(sock_net(sk_vsock(vsk))) =3D=3D VSOCK_NET_MODE_GLOB= AL; } =20 -static inline void vsock_net_set_child_mode(struct net *net, +static inline bool vsock_net_set_child_mode(struct net *net, enum vsock_net_mode mode) { - WRITE_ONCE(net->vsock.child_ns_mode, mode); + int new_locked =3D mode + 1; + int old_locked =3D 0; /* unlocked */ + + if (try_cmpxchg(&net->vsock.child_ns_mode_locked, + &old_locked, new_locked)) { + WRITE_ONCE(net->vsock.child_ns_mode, mode); + return true; + } + + return old_locked =3D=3D new_locked; } =20 static inline enum vsock_net_mode vsock_net_child_mode(struct net *net) diff --git a/include/net/netns/vsock.h b/include/net/netns/vsock.h index b34d69a22fa8..dc8cbe45f406 100644 --- a/include/net/netns/vsock.h +++ b/include/net/netns/vsock.h @@ -17,5 +17,8 @@ struct netns_vsock { =20 enum vsock_net_mode mode; enum vsock_net_mode child_ns_mode; + + /* 0 =3D unlocked, 1 =3D locked to global, 2 =3D locked to local */ + int child_ns_mode_locked; }; #endif /* __NET_NET_NAMESPACE_VSOCK_H */ diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c index 9880756d9eff..50044a838c89 100644 --- a/net/vmw_vsock/af_vsock.c +++ b/net/vmw_vsock/af_vsock.c @@ -90,16 +90,20 @@ * * - /proc/sys/net/vsock/ns_mode (read-only) reports the current namespa= ce's * mode, which is set at namespace creation and immutable thereafter. - * - /proc/sys/net/vsock/child_ns_mode (writable) controls what mode fut= ure + * - /proc/sys/net/vsock/child_ns_mode (write-once) controls what mode f= uture * child namespaces will inherit when created. The initial value match= es * the namespace's own ns_mode. * * Changing child_ns_mode only affects newly created namespaces, not the * current namespace or existing children. A "local" namespace cannot set - * child_ns_mode to "global". At namespace creation, ns_mode is inherited - * from the parent's child_ns_mode. + * child_ns_mode to "global". child_ns_mode is write-once, so that it ma= y be + * configured and locked down by a namespace manager. Writing a different + * value after the first write returns -EBUSY. At namespace creation, ns= _mode + * is inherited from the parent's child_ns_mode. * - * The init_net mode is "global" and cannot be modified. + * The init_net mode is "global" and cannot be modified. The init_net + * child_ns_mode is also write-once, so an init process (e.g. systemd) c= an + * set it to "local" to ensure all new namespaces inherit local mode. * * The modes affect the allocation and accessibility of CIDs as follows: * @@ -2853,7 +2857,8 @@ static int vsock_net_child_mode_string(const struct c= tl_table *table, int write, new_mode =3D=3D VSOCK_NET_MODE_GLOBAL) return -EPERM; =20 - vsock_net_set_child_mode(net, new_mode); + if (!vsock_net_set_child_mode(net, new_mode)) + return -EBUSY; } =20 return 0; --=20 2.47.3 From nobody Fri Apr 3 06:26:50 2026 Received: from mail-yw1-f193.google.com (mail-yw1-f193.google.com [209.85.128.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 99ADA37BE98 for ; Mon, 23 Feb 2026 22:38:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.193 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771886338; cv=none; b=QLugztoUtSdtOfrCJlNK8uVfZdaxz2p8e45ev0FBNlNgQBX/Ifaicwdb1Yhfo6khCd6DGiK9R3SZ60Q50oak+uVnWW5VmZYogZw4oyNks0Wqa9763tF6V9yOuiP9jWR4klMQRFjDhhrZoAIazgFjxQU2gWVpYKXDXIMvtzqKGK0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771886338; c=relaxed/simple; bh=ZIS40BN/lVEtVVMEAyUeO8Q0LmXvqKfPsebwIKGBEeo=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=nNVBkGosvsZTrX/oLyAhToA369CgH5HBwH0XNXkEMJNJBx7n06AtJbW3qv3iKuLm4FzaDbcGxRgU/5NngLeAIy7rSLAzAFYu7j6/5R/4FzCNcj8qJ+2g/wVSsZBVdMNqQ7/EyfK0xfua6V9NGkZtG+Y7ZGxI/TnapWWVL7iMm1A= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=WXwcJ5nH; arc=none smtp.client-ip=209.85.128.193 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="WXwcJ5nH" Received: by mail-yw1-f193.google.com with SMTP id 00721157ae682-79827d28feaso26961547b3.3 for ; Mon, 23 Feb 2026 14:38:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1771886336; x=1772491136; darn=vger.kernel.org; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:from:to:cc:subject:date:message-id :reply-to; bh=0cemh6Unm8avZ318Zd18G/NSlRGlTIfX9gcE2w2y6Xk=; b=WXwcJ5nHT2Wm/PBC1YtI6EPOCYBowHp3Lk1cw+rFZMNUHtzbT9DCmAW/xRAREIgHIB CnIiKyBKNvtAZMG5pxeq1heJClkrSVPTvrFX6EzwNyNnnZ+2b1peTvJ3YNl+K/i3b9It 3SG10I3GoZgiQeLqR+RkMFANZ1ahMjQJRrQhhLT7Q2slVUOgqdPcJ2IgQppjMTVsgohD qx4TerJTJdvZgXiiO3oK6UUFl6VWQsjKft6zZa2ffx8XMU1NmU62gK5aBFvPG5mpS5bW U/ek6YQgDPh+GqfXaffTgfXOdkrHi8+rzPfeSNMt4Ueqs4X+XVLJ6RmLkGSxbqs+Xeal wdBQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1771886336; x=1772491136; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:x-gm-gg:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to; bh=0cemh6Unm8avZ318Zd18G/NSlRGlTIfX9gcE2w2y6Xk=; b=arD4bqMiOr+pTqaFkHWWcDKPwE8v4ne99TRtV0ReRbUKpd8DBba4VcNndlzH+ynnaK btY+C3DU81jhL4/lG04IfVqhXW1CweMEalBW+TMK4IkmoQJtyl4dCBMsZ9O55emG2IB5 ONRxZc+O4QPKzVJqOVSQJu3bN9qdHrVHfYJj2SeOVU/fbp7C+IWS7MyfEALqxiDkioSd BeXVB0xsgnMtrCLb9Y5Ss8Be6ExPLexGPl9raTkhCdJInsVGHVOQsqbA7Fy9sks7zBbh RvkrFsRalAXeTw7bAaMQWgQ8AoFMZGfINR4YXtJdCpzChC5CwzF2DUV8TiNaJUCsmrxT h3Cw== X-Forwarded-Encrypted: i=1; AJvYcCVx2qSr6D3ZYRhV6ZDy+rFka2rf3crgctjj0aCEaDZv51NL+HEI9CqKo3A9UVNmRDRbx3tNnbUP6x/SeDc=@vger.kernel.org X-Gm-Message-State: AOJu0Yz0Ti54gTA8lQCuTSew4t745B337H/ip6lKK/hPlea7Ku3tzePJ n3GH5rkXKVPY0g6qWifSj3on58nKYNC38vnZseX7XO67HklvvL7N5EWN X-Gm-Gg: ATEYQzwcXFq0kRxI4eV6xMWYRgxw7F8hevack7q6cBhBkNEIlkVY0vgnFVZABQDg/G6 me5o2m673LRVPj6pmilJNJYtxI5xAELYUPrNq49pPh4zsR/1M5dnr+fo+lvAv7jBVJgw0+RixRd 0pNx+PEVaWo2RBY5mlGwySywGWQ+BL8sFdSWvOwdz8PW+xTcLKMuKO2tGsM1UKNUKK5PGeVsUKS KFZmzKVeIP+jJVRQeBrSN7gidojUww0U5tWDu5ZQCbcaYGWgp6SkuxPzc0DljcdfVIb/MwTD0aQ LAgtTEBf91LzJjTraAPSvoQGa35DYfgC5j/w7anYq2SUkAvo6RXuBKC61LBYjx1fyRLZVvxp9dw tJL1lNtNX/jVKJ3UpNvK0QIQOsf+DvObL13EpLBLBeUaWJiHcKjNz0gr5iHVqRlgaZWIwucZ8wV eAmE/mR1SF/H2Vv0+15cdPow== X-Received: by 2002:a05:690c:d89:b0:796:34f7:8ea2 with SMTP id 00721157ae682-79828fd308cmr92461117b3.31.1771886335647; Mon, 23 Feb 2026 14:38:55 -0800 (PST) Received: from localhost ([2a03:2880:25ff:58::]) by smtp.gmail.com with ESMTPSA id 00721157ae682-7982dd87fa2sm37132007b3.28.2026.02.23.14.38.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Feb 2026 14:38:55 -0800 (PST) From: Bobby Eshleman Date: Mon, 23 Feb 2026 14:38:34 -0800 Subject: [PATCH net v3 3/3] vsock: document write-once behavior of the child_ns_mode sysctl Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260223-vsock-ns-write-once-v3-3-c0cde6959923@meta.com> References: <20260223-vsock-ns-write-once-v3-0-c0cde6959923@meta.com> In-Reply-To: <20260223-vsock-ns-write-once-v3-0-c0cde6959923@meta.com> 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 X-Mailer: b4 0.14.3 From: Bobby Eshleman Update the vsock child_ns_mode documentation to include the new write-once semantics of setting child_ns_mode. The semantics are implemented in a preceding patch in this series. Signed-off-by: Bobby Eshleman Reviewed-by: Stefano Garzarella --- Changes in v3: - update language to clarify language that first value is locked, but subse= quent writes succeed. --- Documentation/admin-guide/sysctl/net.rst | 3 +++ 1 file changed, 3 insertions(+) diff --git a/Documentation/admin-guide/sysctl/net.rst b/Documentation/admin= -guide/sysctl/net.rst index c10530624f1e..3b2ad61995d4 100644 --- a/Documentation/admin-guide/sysctl/net.rst +++ b/Documentation/admin-guide/sysctl/net.rst @@ -594,6 +594,9 @@ Values: their sockets will only be able to connect within their own namespace. =20 +The first write to ``child_ns_mode`` locks its value. Subsequent writes of= the +same value succeed, but writing a different value returns ``-EBUSY``. + Changing ``child_ns_mode`` only affects namespaces created after the chang= e; it does not modify the current namespace or any existing children. =20 --=20 2.47.3