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@xxxxxxxxxxxxx>
Signed-off-by: Tycho Andersen <tycho.andersen@xxxxxxxxxxxxx>
CC: Eric Biederman <ebiederm@xxxxxxxxxxxx>
CC: Pravin Shelar <pshelar@xxxxxxx>
CC: Justin Pettit <jpettit@xxxxxxxxxx>
CC: "David S. Miller" <davem@xxxxxxxxxxxxx>
---
include/uapi/linux/genetlink.h | 1 +
net/netlink/genetlink.c | 4 ++++
net/openvswitch/datapath.c | 20 ++++++++++----------
3 files changed, 15 insertions(+), 10 deletions(-)
diff --git a/include/uapi/linux/genetlink.h b/include/uapi/linux/genetlink.h
index c3363ba..5512c90 100644
--- a/include/uapi/linux/genetlink.h
+++ b/include/uapi/linux/genetlink.h
@@ -21,6 +21,7 @@ struct genlmsghdr {
#define GENL_CMD_CAP_DO 0x02
#define GENL_CMD_CAP_DUMP 0x04
#define GENL_CMD_CAP_HASPOL 0x08
+#define GENL_UNS_ADMIN_PERM 0x10
/*
* List of reserved static generic netlink identifiers:
diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index f830326..0ffd721 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -580,6 +580,10 @@ static int genl_family_rcv_msg(struct genl_family *family,
!netlink_capable(skb, CAP_NET_ADMIN))
return -EPERM;
+ if ((ops->flags & GENL_UNS_ADMIN_PERM) &&
+ !netlink_ns_capable(skb, net->user_ns, CAP_NET_ADMIN))
+ return -EPERM;
+
if ((nlh->nlmsg_flags & NLM_F_DUMP) == NLM_F_DUMP) {
int rc;
diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index deadfda..d6f7fe9 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -654,7 +654,7 @@ static const struct nla_policy packet_policy[OVS_PACKET_ATTR_MAX + 1] = {
static const 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
}
@@ -1391,12 +1391,12 @@ static const struct nla_policy flow_policy[OVS_FLOW_ATTR_MAX + 1] = {
static const 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
},
@@ -1407,7 +1407,7 @@ static const 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,
},
@@ -1777,12 +1777,12 @@ static const struct nla_policy datapath_policy[OVS_DP_ATTR_MAX + 1] = {
static const 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
},
@@ -1793,7 +1793,7 @@ static const 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,
},
@@ -2158,12 +2158,12 @@ static const struct nla_policy vport_policy[OVS_VPORT_ATTR_MAX + 1] = {
static const 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
},
@@ -2174,7 +2174,7 @@ static const 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,
},
--
2.5.0
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