selinux: remove the BUG_ON() from selinux_skb_xfrm_sid()

Remove the BUG_ON() from selinux_skb_xfrm_sid() and propogate the
error code up to the caller.  Also check the return values in the
only caller function, selinux_skb_peerlbl_sid().
Signed-off-by: Paul Moore <pmoore@redhat.com>
Signed-off-by: Eric Paris <eparis@redhat.com>

security/selinux/hooks.c

@@ -3722,8 +3722,12 @@ static int selinux_skb_peerlbl_sid(struct sk_buff *skb, u16 family, u32 *sid)
 	u32 nlbl_sid;
 	u32 nlbl_type;
 
-	selinux_skb_xfrm_sid(skb, &xfrm_sid);
-	selinux_netlbl_skbuff_getsid(skb, family, &nlbl_type, &nlbl_sid);
+	err = selinux_skb_xfrm_sid(skb, &xfrm_sid);
+	if (unlikely(err))
+		return -EACCES;
+	err = selinux_netlbl_skbuff_getsid(skb, family, &nlbl_type, &nlbl_sid);
+	if (unlikely(err))
+		return -EACCES;
 
 	err = security_net_peersid_resolve(nlbl_sid, nlbl_type, xfrm_sid, sid);
 	if (unlikely(err)) {

security/selinux/include/xfrm.h

@@ -76,10 +76,9 @@ static inline void selinux_xfrm_notify_policyload(void)
 }
 #endif
 
-static inline void selinux_skb_xfrm_sid(struct sk_buff *skb, u32 *sid)
+static inline int selinux_skb_xfrm_sid(struct sk_buff *skb, u32 *sid)
 {
-	int err = selinux_xfrm_decode_session(skb, sid, 0);
-	BUG_ON(err);
+	return selinux_xfrm_decode_session(skb, sid, 0);
 }
 
 #endif /* _SELINUX_XFRM_H_ */