diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index 403b5ecac2c5..3e6477c6082e 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -1850,6 +1850,7 @@ static int xfrm_alloc_userspi(struct sk_buff *skb, struct nlmsghdr *nlh,
 		pcpu_num = nla_get_u32(attrs[XFRMA_SA_PCPU]);
 		if (pcpu_num >= num_possible_cpus()) {
 			err = -EINVAL;
+			NL_SET_ERR_MSG(extack, "pCPU number too big");
 			goto out_noput;
 		}
 	}
@@ -3001,8 +3002,10 @@ static int xfrm_add_acquire(struct sk_buff *skb, struct nlmsghdr *nlh,
 	if (attrs[XFRMA_SA_PCPU]) {
 		x->pcpu_num = nla_get_u32(attrs[XFRMA_SA_PCPU]);
 		err = -EINVAL;
-		if (x->pcpu_num >= num_possible_cpus())
+		if (x->pcpu_num >= num_possible_cpus()) {
+			NL_SET_ERR_MSG(extack, "pCPU number too big");
 			goto free_state;
+		}
 	}
 
 	err = verify_newpolicy_info(&ua->policy, extack);