xfrm: state and policy should fail if XFRMA_IF_ID 0

xfrm ineterface does not allow xfrm if_id = 0
fail to create or update xfrm state and policy.

With this commit:
 ip xfrm policy add src 192.0.2.1 dst 192.0.2.2 dir out if_id 0
 RTNETLINK answers: Invalid argument

 ip xfrm state add src 192.0.2.1 dst 192.0.2.2 proto esp spi 1 \
            reqid 1 mode tunnel aead 'rfc4106(gcm(aes))' \
            0x1111111111111111111111111111111111111111 96 if_id 0
 RTNETLINK answers: Invalid argument

v1->v2 change:
 - add Fixes: tag

Fixes: 9f8550e ("xfrm: fix disable_xfrm sysctl when used on xfrm interfaces")
Signed-off-by: Antony Antony <antony.antony@secunet.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

net/xfrm/xfrm_user.c

@@ -621,8 +621,13 @@ static struct xfrm_state *xfrm_state_construct(struct net *net,
 
  xfrm_smark_init(attrs, &x->props.smark);
 
- if (attrs[XFRMA_IF_ID])
+ if (attrs[XFRMA_IF_ID]) {
  x->if_id = nla_get_u32(attrs[XFRMA_IF_ID]);
+ if (!x->if_id) {
+ err = -EINVAL;
+ goto error;
+ }
+ }
 
  err = __xfrm_init_state(x, false, attrs[XFRMA_OFFLOAD_DEV]);
  if (err)
@@ -1413,8 +1418,13 @@ static int xfrm_alloc_userspi(struct sk_buff *skb, struct nlmsghdr *nlh,
 
  mark = xfrm_mark_get(attrs, &m);
 
- if (attrs[XFRMA_IF_ID])
+ if (attrs[XFRMA_IF_ID]) {
  if_id = nla_get_u32(attrs[XFRMA_IF_ID]);
+ if (!if_id) {
+ err = -EINVAL;
+ goto out_noput;
+ }
+ }
 
  if (p->info.seq) {
  x = xfrm_find_acq_byseq(net, mark, p->info.seq);
@@ -1727,8 +1737,13 @@ static struct xfrm_policy *xfrm_policy_construct(struct net *net, struct xfrm_us
 
  xfrm_mark_get(attrs, &xp->mark);
 
- if (attrs[XFRMA_IF_ID])
+ if (attrs[XFRMA_IF_ID]) {
  xp->if_id = nla_get_u32(attrs[XFRMA_IF_ID]);
+ if (!xp->if_id) {
+ err = -EINVAL;
+ goto error;
+ }
+ }
 
  return xp;
  error: