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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: Simon Horman , Pravin B Shelar , Thomas Graf , Alex Wang , netdev@vger.kernel.org, dev@openvswitch.org, Xiang Mei , Weiming Shi Subject: [PATCH net v5] openvswitch: cap upcall PID array size and pre-size vport replies Date: Wed, 15 Apr 2026 19:46:54 -0700 Message-ID: <20260416024653.153456-2-bestswngs@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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, causing nla_put() to fail with -EMSGSIZE and hitting BUG_ON(err < 0). On systems with unprivileged user namespaces enabled (e.g., Ubuntu default), this is reachable via unshare -Urn since OVS vport mutation operations use GENL_UNS_ADMIN_PERM. 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+0x34c/0x400 Call Trace: genl_family_rcv_msg_doit (net/netlink/genetlink.c:1116) genl_rcv_msg (net/netlink/genetlink.c:1194) netlink_rcv_skb (net/netlink/af_netlink.c:2550) genl_rcv (net/netlink/genetlink.c:1219) netlink_unicast (net/netlink/af_netlink.c:1344) netlink_sendmsg (net/netlink/af_netlink.c:1894) __sys_sendto (net/socket.c:2206) __x64_sys_sendto (net/socket.c:2209) do_syscall_64 (arch/x86/entry/syscall_64.c:63) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) Kernel panic - not syncing: Fatal exception Reject attempts to set more PIDs than nr_cpu_ids in ovs_vport_set_upcall_portids(), and pre-compute the worst-case reply size in ovs_vport_cmd_msg_size() based on that bound, similar to the existing ovs_dp_cmd_msg_size(). nr_cpu_ids matches the cap already used by the per-CPU dispatch configuration on the datapath side (ovs_dp_cmd_fill_info() serialises at most nr_cpu_ids PIDs), so the two sides stay consistent. Fixes: 5cd667b0a456 ("openvswitch: Allow each vport to have an array of 'port_id's.") Reported-by: Xiang Mei Assisted-by: Claude:claude-opus-4-6 Signed-off-by: Weiming Shi --- v5 (per Ilya): - Add blank lines before multi-line comment blocks in ovs_vport_cmd_msg_size() for readability. - Drop parenthetical from the OVS_VPORT_ATTR_UPCALL_PID comment. - Add lore links for previous versions. v4: https://lore.kernel.org/netdev/20260415125121.110874-2-bestswngs@gmail.com - Use nr_cpu_ids instead of num_possible_cpus() for consistency with the per-CPU dispatch on the datapath side. - Annotate ovs_vport_cmd_msg_size() per-attribute; split nested sums. v3: https://lore.kernel.org/netdev/20260413035514.2113886-3-bestswngs@gmail.com - Cap at num_possible_cpus(); add ovs_vport_cmd_msg_size(); keep BUG_ON(); fix Fixes tag. v2: https://lore.kernel.org/netdev/20260411141448.1479933-3-bestswngs@gmail.com - Dynamically size reply skb; drop WARN_ON_ONCE, return plain errors. v1: https://lore.kernel.org/netdev/20260411055915.1224902-2-bestswngs@gmail.com --- net/openvswitch/datapath.c | 35 +++++++++++++++++++++++++++++++++-- net/openvswitch/vport.c | 3 +++ 2 files changed, 36 insertions(+), 2 deletions(-) diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c index e209099218b4..bbbde50fc649 100644 --- a/net/openvswitch/datapath.c +++ b/net/openvswitch/datapath.c @@ -2184,9 +2184,40 @@ static int ovs_vport_cmd_fill_info(struct vport *vport, struct sk_buff *skb, return err; } +static size_t ovs_vport_cmd_msg_size(void) +{ + size_t msgsize = NLMSG_ALIGN(sizeof(struct ovs_header)); + + msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_PORT_NO */ + msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_TYPE */ + msgsize += nla_total_size(IFNAMSIZ); /* OVS_VPORT_ATTR_NAME */ + msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_IFINDEX */ + msgsize += nla_total_size(sizeof(s32)); /* OVS_VPORT_ATTR_NETNSID */ + + /* OVS_VPORT_ATTR_STATS */ + msgsize += nla_total_size_64bit(sizeof(struct ovs_vport_stats)); + + /* OVS_VPORT_ATTR_UPCALL_STATS(OVS_VPORT_UPCALL_ATTR_SUCCESS + + * OVS_VPORT_UPCALL_ATTR_FAIL) + */ + msgsize += nla_total_size(nla_total_size_64bit(sizeof(u64)) + + nla_total_size_64bit(sizeof(u64))); + + /* OVS_VPORT_ATTR_UPCALL_PID */ + msgsize += nla_total_size(nr_cpu_ids * sizeof(u32)); + + /* OVS_VPORT_ATTR_OPTIONS(OVS_TUNNEL_ATTR_DST_PORT + + * OVS_TUNNEL_ATTR_EXTENSION(OVS_VXLAN_EXT_GBP)) + */ + msgsize += nla_total_size(nla_total_size(sizeof(u16)) + + nla_total_size(nla_total_size(0))); + + return msgsize; +} + static struct sk_buff *ovs_vport_cmd_alloc_info(void) { - return nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL); + return genlmsg_new(ovs_vport_cmd_msg_size(), GFP_KERNEL); } /* Called with ovs_mutex, only via ovs_dp_notify_wq(). */ @@ -2196,7 +2227,7 @@ struct sk_buff *ovs_vport_cmd_build_info(struct vport *vport, struct net *net, struct sk_buff *skb; int retval; - skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL); + skb = ovs_vport_cmd_alloc_info(); if (!skb) return ERR_PTR(-ENOMEM); diff --git a/net/openvswitch/vport.c b/net/openvswitch/vport.c index 23f629e94a36..56b2e2d1a749 100644 --- a/net/openvswitch/vport.c +++ b/net/openvswitch/vport.c @@ -406,6 +406,9 @@ int ovs_vport_set_upcall_portids(struct vport *vport, const struct nlattr *ids) if (!nla_len(ids) || nla_len(ids) % sizeof(u32)) return -EINVAL; + if (nla_len(ids) / sizeof(u32) > nr_cpu_ids) + return -EINVAL; + old = ovsl_dereference(vport->upcall_portids); vport_portids = kmalloc(sizeof(*vport_portids) + nla_len(ids), -- 2.43.0