Re: [PATCH net 2/2] openvswitch: check for null return for nla_nest_start in datapath

The call to nla_nest_start when forming packet messages can lead to a NULL
return so it's possible for attr to become NULL and we can potentially
get a NULL pointer dereference on attr.  Fix this by checking for
a NULL return.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=200537
Fixes: 8f0aad6f35f7 ("openvswitch: Extend packet attribute for egress tunnel info")
Signed-off-by: Stephen Hemminger <redacted>
---
 net/openvswitch/datapath.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index 0f5ce77460d4..93c3eb635827 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c

@@ -460,6 +460,10 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,

        if (upcall_info->egress_tun_info) {
                nla = nla_nest_start(user_skb, OVS_PACKET_ATTR_EGRESS_TUN_KEY);
+               if (!nla) {
+                       err = -EMSGSIZE;
+                       goto out;
+               }
                err = ovs_nla_put_tunnel_info(user_skb,
                                              upcall_info->egress_tun_info);
                BUG_ON(err);

@@ -468,6 +472,10 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,

        if (upcall_info->actions_len) {
                nla = nla_nest_start(user_skb, OVS_PACKET_ATTR_ACTIONS);
+               if (!nla) {
+                       err = -EMSGSIZE;
+                       goto out;
+               }
                err = ovs_nla_put_actions(upcall_info->actions,
                                          upcall_info->actions_len,
                                          user_skb);