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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-488d5d85ae9sm62753825e9.3.2026.04.11.05.23.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 11 Apr 2026 05:23:21 -0700 (PDT) Date: Sat, 11 Apr 2026 13:23:19 +0100 From: David Laight To: Weiming Shi Cc: Aaron Conole , Eelco Chaudron , Ilya Maximets , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Pravin B Shelar , Flavio Leitner , Mark Gray , netdev@vger.kernel.org, dev@openvswitch.org, linux-kernel@vger.kernel.org, Xiang Mei Subject: Re: [PATCH net] openvswitch: fix kernel panic from oversized vport upcall PID arrays Message-ID: <20260411132319.560dcb22@pumpkin> In-Reply-To: <20260411055915.1224902-2-bestswngs@gmail.com> References: <20260411055915.1224902-2-bestswngs@gmail.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) 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=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 10 Apr 2026 22:59:16 -0700 Weiming Shi wrote: > The vport netlink reply helpers allocate a fixed-size skb with > nlmsg_new(NLMSG_DEFAULT_SIZE, ...) but serialize the full upcall PID > array via ovs_vport_get_upcall_portids(). Since > ovs_vport_set_upcall_portids() accepts any non-zero multiple of > sizeof(u32) with no upper bound, a CAP_NET_ADMIN user can install a > PID array large enough to overflow the reply buffer. When the > subsequent nla_put() fails with -EMSGSIZE, five BUG_ON(err < 0) sites > fire and panic the kernel. On systems with unprivileged user namespaces > enabled (e.g., Ubuntu default), this is reachable via unshare -Urn. > > kernel BUG at net/openvswitch/datapath.c:2414! > Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI > CPU: 1 UID: 0 PID: 65 Comm: poc Not tainted 7.0.0-rc7-00195-geb216e422044 #1 > RIP: 0010:ovs_vport_cmd_set (net/openvswitch/datapath.c:2414 (discriminator 1)) > Call Trace: > > genl_family_rcv_msg_doit (net/netlink/genetlink.c:1116) > genl_rcv_msg (net/netlink/genetlink.c:1194 net/netlink/genetlink.c:1209) > netlink_rcv_skb (net/netlink/af_netlink.c:2550) > genl_rcv (net/netlink/genetlink.c:1219) > netlink_unicast (net/netlink/af_netlink.c:1319 net/netlink/af_netlink.c:1344) > netlink_sendmsg (net/netlink/af_netlink.c:1894) > __sys_sendto (net/socket.c:2206 (discriminator 1)) > __x64_sys_sendto (net/socket.c:2209) > do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1)) > entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) > > Kernel panic - not syncing: Fatal exception > > Dynamically compute the reply skb size based on the vport's actual PID > array length instead of using a fixed NLMSG_DEFAULT_SIZE, and replace > the BUG_ON() calls with WARN_ON_ONCE() plus graceful error returns. IIRC WARN_ON_ONCE() will still panic all the systems with panic-on_warn set. David