Skip to content

Commit 7cc9f70

Browse files
borkmanndavem330
borkmann
authored and
davem330
committed
ipvlan: disallow userns cap_net_admin to change global mode/flags
When running Docker with userns isolation e.g. --userns-remap="default" and spawning up some containers with CAP_NET_ADMIN under this realm, I noticed that link changes on ipvlan slave device inside that container can affect all devices from this ipvlan group which are in other net namespaces where the container should have no permission to make changes to, such as the init netns, for example. This effectively allows to undo ipvlan private mode and switch globally to bridge mode where slaves can communicate directly without going through hostns, or it allows to switch between global operation mode (l2/l3/l3s) for everyone bound to the given ipvlan master device. libnetwork plugin here is creating an ipvlan master and ipvlan slave in hostns and a slave each that is moved into the container's netns upon creation event. * In hostns: # ip -d a [...] 8: cilium_host@bond0: <BROADCAST,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000 link/ether 0c:c4:7a:e1:3d:cc brd ff:ff:ff:ff:ff:ff promiscuity 0 minmtu 68 maxmtu 65535 ipvlan mode l3 bridge numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 inet 10.41.0.1/32 scope link cilium_host valid_lft forever preferred_lft forever [...] * Spawn container & change ipvlan mode setting inside of it: # docker run -dt --cap-add=NET_ADMIN --network cilium-net --name client -l app=test cilium/netperf 9fff485d69dcb5ce37c9e33ca20a11ccafc236d690105aadbfb77e4f4170879c # docker exec -ti client ip -d a [...] 10: cilium0@if4: <BROADCAST,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000 link/ether 0c:c4:7a:e1:3d:cc brd ff:ff:ff:ff:ff:ff promiscuity 0 minmtu 68 maxmtu 65535 ipvlan mode l3 bridge numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 inet 10.41.197.43/32 brd 10.41.197.43 scope global cilium0 valid_lft forever preferred_lft forever # docker exec -ti client ip link change link cilium0 name cilium0 type ipvlan mode l2 # docker exec -ti client ip -d a [...] 10: cilium0@if4: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000 link/ether 0c:c4:7a:e1:3d:cc brd ff:ff:ff:ff:ff:ff promiscuity 0 minmtu 68 maxmtu 65535 ipvlan mode l2 bridge numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 inet 10.41.197.43/32 brd 10.41.197.43 scope global cilium0 valid_lft forever preferred_lft forever * In hostns (mode switched to l2): # ip -d a [...] 8: cilium_host@bond0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000 link/ether 0c:c4:7a:e1:3d:cc brd ff:ff:ff:ff:ff:ff promiscuity 0 minmtu 68 maxmtu 65535 ipvlan mode l2 bridge numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 inet 10.41.0.1/32 scope link cilium_host valid_lft forever preferred_lft forever [...] Same l3 -> l2 switch would also happen by creating another slave inside the container's network namespace when specifying the existing cilium0 link to derive the actual (bond0) master: # docker exec -ti client ip link add link cilium0 name cilium1 type ipvlan mode l2 # docker exec -ti client ip -d a [...] 2: cilium1@if4: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000 link/ether 0c:c4:7a:e1:3d:cc brd ff:ff:ff:ff:ff:ff promiscuity 0 minmtu 68 maxmtu 65535 ipvlan mode l2 bridge numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 10: cilium0@if4: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000 link/ether 0c:c4:7a:e1:3d:cc brd ff:ff:ff:ff:ff:ff promiscuity 0 minmtu 68 maxmtu 65535 ipvlan mode l2 bridge numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 inet 10.41.197.43/32 brd 10.41.197.43 scope global cilium0 valid_lft forever preferred_lft forever * In hostns: # ip -d a [...] 8: cilium_host@bond0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000 link/ether 0c:c4:7a:e1:3d:cc brd ff:ff:ff:ff:ff:ff promiscuity 0 minmtu 68 maxmtu 65535 ipvlan mode l2 bridge numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 inet 10.41.0.1/32 scope link cilium_host valid_lft forever preferred_lft forever [...] One way to mitigate it is to check CAP_NET_ADMIN permissions of the ipvlan master device's ns, and only then allow to change mode or flags for all devices bound to it. Above two cases are then disallowed after the patch. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Mahesh Bandewar <maheshb@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
1 parent d1f20c0 commit 7cc9f70

File tree

1 file changed

+4
-0
lines changed

1 file changed

+4
-0
lines changed

‎drivers/net/ipvlan/ipvlan_main.c

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -499,6 +499,8 @@ static int ipvlan_nl_changelink(struct net_device *dev,
499499

500500
if (!data)
501501
return 0;
502+
if (!ns_capable(dev_net(ipvlan->phy_dev)->user_ns, CAP_NET_ADMIN))
503+
return -EPERM;
502504

503505
if (data[IFLA_IPVLAN_MODE]) {
504506
u16 nmode = nla_get_u16(data[IFLA_IPVLAN_MODE]);
@@ -601,6 +603,8 @@ int ipvlan_link_new(struct net *src_net, struct net_device *dev,
601603
struct ipvl_dev *tmp = netdev_priv(phy_dev);
602604

603605
phy_dev = tmp->phy_dev;
606+
if (!ns_capable(dev_net(phy_dev)->user_ns, CAP_NET_ADMIN))
607+
return -EPERM;
604608
} else if (!netif_is_ipvlan_port(phy_dev)) {
605609
/* Exit early if the underlying link is invalid or busy */
606610
if (phy_dev->type != ARPHRD_ETHER ||

0 commit comments

Comments
 (0)