datapath: backport: openvswitch: allow management from inside user namespaces

Upstream commit:
    commit 4a92602aa1cd5bbaeedbd9536ff992f7d26fe9d1
    Author: Tycho Andersen <tycho.andersen@canonical.com>

    openvswitch: allow management from inside user namespaces

    Operations with the GENL_ADMIN_PERM flag fail permissions checks because
    this flag means we call netlink_capable, which uses the init user ns.

    Instead, let's introduce a new flag, GENL_UNS_ADMIN_PERM for operations
    which should be allowed inside a user namespace.

    The motivation for this is to be able to run openvswitch in unprivileged
    containers. I've tested this and it seems to work, but I really have no
    idea about the security consequences of this patch, so thoughts would be
    much appreciated.

    v2: use the GENL_UNS_ADMIN_PERM flag instead of a check in each function
    v3: use separate ifs for UNS_ADMIN_PERM and ADMIN_PERM, instead of one
        massive one

    Reported-by: James Page <james.page@canonical.com>
    Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
    CC: Eric Biederman <ebiederm@xmission.com>
    CC: Pravin Shelar <pshelar@ovn.org>
    CC: Justin Pettit <jpettit@ovn.org>
    CC: "David S. Miller" <davem@davemloft.net>
    Acked-by: Pravin B Shelar <pshelar@ovn.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Pravin B Shelar <pshelar@ovn.org>
Acked-by: Jesse Gross <jesse@kernel.org>

3 files changed, 21 insertions, 10 deletions

diff --git a/datapath/datapath.c b/datapath/datapath.c
index 2540df1a5..56bb86d54 100644
--- a/datapath/datapath.c
+++ b/datapath/datapath.c
@@ -683,7 +683,7 @@ static const struct nla_policy packet_policy[OVS_PACKET_ATTR_MAX + 1] = {
 
 static struct genl_ops dp_packet_genl_ops[] = {
 	{ .cmd = OVS_PACKET_CMD_EXECUTE,
-	  .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
+	  .flags = GENL_UNS_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
 	  .policy = packet_policy,
 	  .doit = ovs_packet_cmd_execute
 	}
@@ -1423,12 +1423,12 @@ static const struct nla_policy flow_policy[OVS_FLOW_ATTR_MAX + 1] = {
 
 static struct genl_ops dp_flow_genl_ops[] = {
 	{ .cmd = OVS_FLOW_CMD_NEW,
-	  .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
+	  .flags = GENL_UNS_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
 	  .policy = flow_policy,
 	  .doit = ovs_flow_cmd_new
 	},
 	{ .cmd = OVS_FLOW_CMD_DEL,
-	  .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
+	  .flags = GENL_UNS_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
 	  .policy = flow_policy,
 	  .doit = ovs_flow_cmd_del
 	},
@@ -1439,7 +1439,7 @@ static struct genl_ops dp_flow_genl_ops[] = {
 	  .dumpit = ovs_flow_cmd_dump
 	},
 	{ .cmd = OVS_FLOW_CMD_SET,
-	  .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
+	  .flags = GENL_UNS_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
 	  .policy = flow_policy,
 	  .doit = ovs_flow_cmd_set,
 	},
@@ -1808,12 +1808,12 @@ static const struct nla_policy datapath_policy[OVS_DP_ATTR_MAX + 1] = {
 
 static struct genl_ops dp_datapath_genl_ops[] = {
 	{ .cmd = OVS_DP_CMD_NEW,
-	  .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
+	  .flags = GENL_UNS_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
 	  .policy = datapath_policy,
 	  .doit = ovs_dp_cmd_new
 	},
 	{ .cmd = OVS_DP_CMD_DEL,
-	  .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
+	  .flags = GENL_UNS_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
 	  .policy = datapath_policy,
 	  .doit = ovs_dp_cmd_del
 	},
@@ -1824,7 +1824,7 @@ static struct genl_ops dp_datapath_genl_ops[] = {
 	  .dumpit = ovs_dp_cmd_dump
 	},
 	{ .cmd = OVS_DP_CMD_SET,
-	  .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
+	  .flags = GENL_UNS_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
 	  .policy = datapath_policy,
 	  .doit = ovs_dp_cmd_set,
 	},
@@ -2188,12 +2188,12 @@ static const struct nla_policy vport_policy[OVS_VPORT_ATTR_MAX + 1] = {
 
 static struct genl_ops dp_vport_genl_ops[] = {
 	{ .cmd = OVS_VPORT_CMD_NEW,
-	  .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
+	  .flags = GENL_UNS_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
 	  .policy = vport_policy,
 	  .doit = ovs_vport_cmd_new
 	},
 	{ .cmd = OVS_VPORT_CMD_DEL,
-	  .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
+	  .flags = GENL_UNS_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
 	  .policy = vport_policy,
 	  .doit = ovs_vport_cmd_del
 	},
@@ -2204,7 +2204,7 @@ static struct genl_ops dp_vport_genl_ops[] = {
 	  .dumpit = ovs_vport_cmd_dump
 	},
 	{ .cmd = OVS_VPORT_CMD_SET,
-	  .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
+	  .flags = GENL_UNS_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
 	  .policy = vport_policy,
 	  .doit = ovs_vport_cmd_set,
 	},
diff --git a/datapath/linux/Modules.mk b/datapath/linux/Modules.mk
index ef080837b..6ac2bb45d 100644
--- a/datapath/linux/Modules.mk
+++ b/datapath/linux/Modules.mk
@@ -39,6 +39,7 @@ openvswitch_headers += \
 	linux/compat/include/linux/err.h \
 	linux/compat/include/linux/etherdevice.h \
 	linux/compat/include/linux/flex_array.h \
+	linux/compat/include/linux/genetlink.h \
 	linux/compat/include/linux/if.h \
 	linux/compat/include/linux/if_ether.h \
 	linux/compat/include/linux/if_link.h \
diff --git a/datapath/linux/compat/include/linux/genetlink.h b/datapath/linux/compat/include/linux/genetlink.h
new file mode 100644
index 000000000..de55e4017
--- /dev/null
+++ b/datapath/linux/compat/include/linux/genetlink.h
@@ -0,0 +1,10 @@
+#ifndef _UAPI__LINUX_GENERIC_NETLINK_WRAPPER_H
+#define _UAPI__LINUX_GENERIC_NETLINK_WRAPPER_H
+
+#include_next <linux/genetlink.h>
+
+#ifndef GENL_UNS_ADMIN_PERM
+#define GENL_UNS_ADMIN_PERM GENL_ADMIN_PERM
+#endif
+
+#endif