From 1926407a4ab0e59d5a27bed7b82029b356d80fa0 Mon Sep 17 00:00:00 2001 From: Ilya Maximets Date: Wed, 9 Mar 2022 23:20:33 +0100 Subject: [PATCH] net: openvswitch: fix uAPI incompatibility with existing user space Few years ago OVS user space made a strange choice in the commit [1] to define types only valid for the user space inside the copy of a kernel uAPI header. '#ifndef __KERNEL__' and another attribute was added later. This leads to the inevitable clash between user space and kernel types when the kernel uAPI is extended. The issue was unveiled with the addition of a new type for IPv6 extension header in kernel uAPI. When kernel provides the OVS_KEY_ATTR_IPV6_EXTHDRS attribute to the older user space application, application tries to parse it as OVS_KEY_ATTR_PACKET_TYPE and discards the whole netlink message as malformed. Since OVS_KEY_ATTR_IPV6_EXTHDRS is supplied along with every IPv6 packet that goes to the user space, IPv6 support is fully broken. Fixing that by bringing these user space attributes to the kernel uAPI to avoid the clash. Strictly speaking this is not the problem of the kernel uAPI, but changing it is the only way to avoid breakage of the older user space applications at this point. These 2 types are explicitly rejected now since they should not be passed to the kernel. Additionally, OVS_KEY_ATTR_TUNNEL_INFO moved out from the '#ifdef __KERNEL__' as there is no good reason to hide it from the userspace. And it's also explicitly rejected now, because it's for in-kernel use only. Comments with warnings were added to avoid the problem coming back. (1 << type) converted to (1ULL << type) to avoid integer overflow on OVS_KEY_ATTR_IPV6_EXTHDRS, since it equals 32 now. [1] beb75a40fdc2 ("userspace: Switching of L3 packets in L2 pipeline") Fixes: 28a3f0601727 ("net: openvswitch: IPv6: Add IPv6 extension header support") Link: https://lore.kernel.org/netdev/3adf00c7-fe65-3ef4-b6d7-6d8a0cad8a5f@nvidia.com Link: https://github.com/openvswitch/ovs/commit/beb75a40fdc295bfd6521b0068b4cd12f6de507c Reported-by: Roi Dayan Signed-off-by: Ilya Maximets Acked-by: Nicolas Dichtel Acked-by: Aaron Conole Link: https://lore.kernel.org/r/20220309222033.3018976-1-i.maximets@ovn.org Signed-off-by: Jakub Kicinski --- include/uapi/linux/openvswitch.h | 18 ++++++++++++++---- net/openvswitch/flow_netlink.c | 13 ++++++++++--- 2 files changed, 24 insertions(+), 7 deletions(-) diff --git a/include/uapi/linux/openvswitch.h b/include/uapi/linux/openvswitch.h index 9d1710f..ce3e173 100644 --- a/include/uapi/linux/openvswitch.h +++ b/include/uapi/linux/openvswitch.h @@ -351,11 +351,21 @@ enum ovs_key_attr { OVS_KEY_ATTR_CT_ORIG_TUPLE_IPV4, /* struct ovs_key_ct_tuple_ipv4 */ OVS_KEY_ATTR_CT_ORIG_TUPLE_IPV6, /* struct ovs_key_ct_tuple_ipv6 */ OVS_KEY_ATTR_NSH, /* Nested set of ovs_nsh_key_* */ - OVS_KEY_ATTR_IPV6_EXTHDRS, /* struct ovs_key_ipv6_exthdr */ -#ifdef __KERNEL__ - OVS_KEY_ATTR_TUNNEL_INFO, /* struct ip_tunnel_info */ -#endif + /* User space decided to squat on types 29 and 30. They are defined + * below, but should not be sent to the kernel. + * + * WARNING: No new types should be added unless they are defined + * for both kernel and user space (no 'ifdef's). It's hard + * to keep compatibility otherwise. + */ + OVS_KEY_ATTR_PACKET_TYPE, /* be32 packet type */ + OVS_KEY_ATTR_ND_EXTENSIONS, /* IPv6 Neighbor Discovery extensions */ + + OVS_KEY_ATTR_TUNNEL_INFO, /* struct ip_tunnel_info. + * For in-kernel use only. + */ + OVS_KEY_ATTR_IPV6_EXTHDRS, /* struct ovs_key_ipv6_exthdr */ __OVS_KEY_ATTR_MAX }; diff --git a/net/openvswitch/flow_netlink.c b/net/openvswitch/flow_netlink.c index 8b41248..5176f6c 100644 --- a/net/openvswitch/flow_netlink.c +++ b/net/openvswitch/flow_netlink.c @@ -346,7 +346,7 @@ size_t ovs_key_attr_size(void) /* Whenever adding new OVS_KEY_ FIELDS, we should consider * updating this function. */ - BUILD_BUG_ON(OVS_KEY_ATTR_TUNNEL_INFO != 30); + BUILD_BUG_ON(OVS_KEY_ATTR_MAX != 32); return nla_total_size(4) /* OVS_KEY_ATTR_PRIORITY */ + nla_total_size(0) /* OVS_KEY_ATTR_TUNNEL */ @@ -482,7 +482,14 @@ static int __parse_flow_nlattrs(const struct nlattr *attr, return -EINVAL; } - if (attrs & (1 << type)) { + if (type == OVS_KEY_ATTR_PACKET_TYPE || + type == OVS_KEY_ATTR_ND_EXTENSIONS || + type == OVS_KEY_ATTR_TUNNEL_INFO) { + OVS_NLERR(log, "Key type %d is not supported", type); + return -EINVAL; + } + + if (attrs & (1ULL << type)) { OVS_NLERR(log, "Duplicate key (type %d).", type); return -EINVAL; } @@ -495,7 +502,7 @@ static int __parse_flow_nlattrs(const struct nlattr *attr, } if (!nz || !is_all_zero(nla_data(nla), nla_len(nla))) { - attrs |= 1 << type; + attrs |= 1ULL << type; a[type] = nla; } } -- 2.7.4