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>

1 files changed, 5 insertions, 5 deletions

diff --git a/net/xfrm/xfrm_interface.c b/net/xfrm/xfrm_interface.c
index 74868f9d81fb..2310dc9e35c2 100644
--- 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)