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Sun, 08 Nov 2026 04:34:50 -0800 (PST) Received: from houminxi ([61.170.225.237]) by smtp.gmail.com with ESMTPSA id 00721157ae682-8b36be7d88dsm13475627b3.39.2026.11.08.04.34.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 08 Nov 2026 04:34:49 -0800 (PST) From: Minxi Hou To: netdev@vger.kernel.org Cc: Aaron Conole , Eelco Chaudron , Ilya Maximets , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Shuah Khan , Jamal Hadi Salim , Paul Blakey , dev@openvswitch.org, linux-kselftest@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH net v2 1/2] net: openvswitch: do not record user features when the change fails Date: Sun, 8 Nov 2026 07:34:23 -0500 Message-ID: <20261108123424.2825403-2-houminxi@gmail.com> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261108123424.2825403-1-houminxi@gmail.com> References: <20261108123424.2825403-1-houminxi@gmail.com> X-Mailing-List: netdev@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit ovs_dp_change() stores the new features in dp->user_features before it updates the per-cpu upcall port IDs, and that update fails when the per-cpu-pids attribute is empty or its length is not a multiple of four. The request returns -EINVAL with the new features already recorded. The features decide whether the tc skb extension static key is enabled, but the code that enables or disables the key runs after the failing call, so it does not run for the failed request. dp->user_features then claims TC_RECIRC_SHARING is set while tc_skb_ext_tc_enable() was not called, and a later request that clears the bit calls tc_skb_ext_tc_disable() for an enable that never happened. tc_skb_ext_tc is one static key for the whole host. cls_flower, the bridge, the flow dissector and OVS hold references to it, and the key stays on while any of them holds one. The count ends up one short and reaches zero while other users still hold a reference, so recirc sharing in every datapath goes off with it, as does the skb extension allocation in tc, in the flow dissector and in the bridge. A disable on a count of zero also reaches the imbalance check in static_key_dec_not_one() in kernel/jump_label.c and warns there, which panics a host that runs with panic_on_warn. The opposite ordering is possible as well: a failing request that drops the bit leaves the key enabled for good. The request only needs CAP_NET_ADMIN, which a user namespace that owns a network namespace provides. datapath_policy has no entry for OVS_DP_ATTR_PER_CPU_PIDS and the operation skips strict validation, so an empty attribute reaches the check that fails. Keep the new features in the local variable until the request has gone through, and use that variable for the enable and disable decisions. A failed OVS_DP_CMD_SET then leaves both the features and the key alone. Two other paths touch the bit without keeping the key in step: ovs_dp_reset_user_features() clears it without disabling the key, and a new datapath that fails after ovs_dp_change() succeeded is freed without disabling it. Both predate this change and are left alone here, so a failed OVS_DP_CMD_NEW and the reset that follows it still leave the key one enable ahead. The selftest in the next patch sends a set request that fails on an empty per-cpu-pids and reads the features back; it fails without this change and passes with it. The openvswitch selftest suite passes with the change applied. Fixes: 35d39fecbc24 ("net/sched: Enable tc skb ext allocation on chain miss only when needed") Cc: stable@vger.kernel.org Signed-off-by: Minxi Hou --- net/openvswitch/datapath.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c index b2a0b09fd4a5..00043aef2d03 100644 --- a/net/openvswitch/datapath.c +++ b/net/openvswitch/datapath.c @@ -1801,9 +1801,7 @@ static int ovs_dp_change(struct datapath *dp, struct nlattr *a[]) return err; } - dp->user_features = user_features; - - if (dp->user_features & OVS_DP_F_DISPATCH_UPCALL_PER_CPU && + if (user_features & OVS_DP_F_DISPATCH_UPCALL_PER_CPU && a[OVS_DP_ATTR_PER_CPU_PIDS]) { /* Upcall Netlink Port IDs have been updated */ err = ovs_dp_set_upcall_portids(dp, @@ -1812,10 +1810,12 @@ static int ovs_dp_change(struct datapath *dp, struct nlattr *a[]) return err; } - if ((dp->user_features & OVS_DP_F_TC_RECIRC_SHARING) && + dp->user_features = user_features; + + if ((user_features & OVS_DP_F_TC_RECIRC_SHARING) && !(old_features & OVS_DP_F_TC_RECIRC_SHARING)) tc_skb_ext_tc_enable(); - else if (!(dp->user_features & OVS_DP_F_TC_RECIRC_SHARING) && + else if (!(user_features & OVS_DP_F_TC_RECIRC_SHARING) && (old_features & OVS_DP_F_TC_RECIRC_SHARING)) tc_skb_ext_tc_disable(); -- 2.56.0