xfrm interface: avoid corruption on changelink

The new parameters must not be stored in the netdev_priv() before
validation, it may corrupt the interface. Note also that if data is NULL,
only a memset() is done.

$ ip link add xfrm1 type xfrm dev lo if_id 1
$ ip link add xfrm2 type xfrm dev lo if_id 2
$ ip link set xfrm1 type xfrm dev lo if_id 2
RTNETLINK answers: File exists
$ ip -d link list dev xfrm1
5: xfrm1@lo: <NOARP> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/none 00:00:00:00:00:00 brd 00:00:00:00:00:00 promiscuity 0 minmtu 68 maxmtu 1500
    xfrm if_id 0x2 addrgenmode eui64 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535

=> "if_id 0x2"

Fixes: f203b76d7809 ("xfrm: Add virtual xfrm interfaces")
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Tested-by: Julien Floret <julien.floret@6wind.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

diff --git a/net/xfrm/xfrm_interface.c b/net/xfrm/xfrm_interface.c
index 74868f9..2310dc9 100644 (file)
--- a/net/xfrm/xfrm_interface.c
+++ b/net/xfrm/xfrm_interface.c
@@ -671,12 +671,12 @@ static int xfrmi_changelink(struct net_device *dev, struct nlattr *tb[],
                           struct nlattr *data[],
                           struct netlink_ext_ack *extack)
 {
-       struct xfrm_if *xi = netdev_priv(dev);
        struct net *net = dev_net(dev);
+       struct xfrm_if_parms p;
+       struct xfrm_if *xi;
 
-       xfrmi_netlink_parms(data, &xi->p);
-
-       xi = xfrmi_locate(net, &xi->p);
+       xfrmi_netlink_parms(data, &p);
+       xi = xfrmi_locate(net, &p);
        if (!xi) {
                xi = netdev_priv(dev);
        } else {
@@ -684,7 +684,7 @@ static int xfrmi_changelink(struct net_device *dev, struct nlattr *tb[],
                        return -EEXIST;
        }
 
-       return xfrmi_update(xi, &xi->p);
+       return xfrmi_update(xi, &p);
 }
 
 static size_t xfrmi_get_size(const struct net_device *dev)