netinet*: update *mp to pass the proper value back

In ip6_[direct_]input() we are looping over the extension headers
to deal with the next header.  We pass a pointer to an mbuf pointer
to the handling functions.  In certain cases the mbuf can be updated
there and we need to pass the new one back.  That missing in
dest6_input() and route6_input().  In tcp6_input() we should also
update it before we call tcp_input().

In addition to that mark the mbuf NULL all the times when we return
that we are done with handling the packet and no next header should
be checked (IPPROTO_DONE).  This will eventually allow us to assert
proper behaviour and catch the above kind of errors more easily,
expecting *mp to always be set.

This change is extracted from a larger patch and not an exhaustive
change across the entire stack yet.

PR:			240135
Reported by:		prabhakar.lakhera gmail.com
MFC after:		3 weeks
Sponsored by:		Netflix

sys/netinet/tcp_input.c

@@ -530,11 +530,13 @@ tcp6_input(struct mbuf **mp, int *offp, int proto)
 		ifa_free(&ia6->ia_ifa);
 		icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
 			    (caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
+		*mp = NULL;
 		return (IPPROTO_DONE);
 	}
 	if (ia6)
 		ifa_free(&ia6->ia_ifa);
 
+	*mp = m;
 	return (tcp_input(mp, offp, proto));
 }
 #endif /* INET6 */

sys/netinet6/dest6.c

@@ -113,17 +113,21 @@ dest6_input(struct mbuf **mp, int *offp, int proto)
 		default:		/* unknown option */
 			optlen = ip6_unknown_opt(opt, m,
 			    opt - mtod(m, u_int8_t *));
-			if (optlen == -1)
+			if (optlen == -1) {
+				*mp = NULL;
 				return (IPPROTO_DONE);
+			}
 			optlen += 2;
 			break;
 		}
 	}
 
 	*offp = off;
+	*mp = m;
 	return (dstopts->ip6d_nxt);
 
   bad:
 	m_freem(m);
+	*mp = NULL;
 	return (IPPROTO_DONE);
 }

sys/netinet6/frag6.c

@@ -419,6 +419,7 @@ frag6_input(struct mbuf **mp, int *offp, int proto)
 	if (ip6->ip6_plen == 0) {
 		icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offset);
 		in6_ifstat_inc(dstifp, ifs6_reass_fail);
+		*mp = NULL;
 		return (IPPROTO_DONE);
 	}
 
@@ -433,6 +434,7 @@ frag6_input(struct mbuf **mp, int *offp, int proto)
 		icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
 		    offsetof(struct ip6_hdr, ip6_plen));
 		in6_ifstat_inc(dstifp, ifs6_reass_fail);
+		*mp = NULL;
 		return (IPPROTO_DONE);
 	}
 
@@ -476,6 +478,7 @@ frag6_input(struct mbuf **mp, int *offp, int proto)
 		    offsetof(struct ip6_hdr, ip6_plen));
 		in6_ifstat_inc(dstifp, ifs6_reass_fail);
 		IP6STAT_INC(ip6s_fragdropped);
+		*mp = NULL;
 		return (IPPROTO_DONE);
 	}
 
@@ -611,6 +614,7 @@ frag6_input(struct mbuf **mp, int *offp, int proto)
 			icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
 			    offset - sizeof(struct ip6_frag) +
 			    offsetof(struct ip6_frag, ip6f_offlg));
+			*mp = NULL;
 			return (IPPROTO_DONE);
 		}
 	} else if (fragoff + frgpartlen > IPV6_MAXPACKET) {
@@ -627,6 +631,7 @@ frag6_input(struct mbuf **mp, int *offp, int proto)
 		icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
 		    offset - sizeof(struct ip6_frag) +
 		    offsetof(struct ip6_frag, ip6f_offlg));
+		*mp = NULL;
 		return (IPPROTO_DONE);
 	}
 
@@ -777,6 +782,7 @@ frag6_input(struct mbuf **mp, int *offp, int proto)
 				frag6_freef(q6, bucket);
 			}
 			IP6QB_UNLOCK(bucket);
+			*mp = NULL;
 			return (IPPROTO_DONE);
 		}
 		plen += af6->ip6af_frglen;
@@ -788,6 +794,7 @@ frag6_input(struct mbuf **mp, int *offp, int proto)
 			frag6_freef(q6, bucket);
 		}
 		IP6QB_UNLOCK(bucket);
+		*mp = NULL;
 		return (IPPROTO_DONE);
 	}
 
@@ -877,6 +884,7 @@ frag6_input(struct mbuf **mp, int *offp, int proto)
 #ifdef RSS
 	/* Queue/dispatch for reprocessing. */
 	netisr_dispatch(NETISR_IPV6_DIRECT, m);
+	*mp = NULL;
 	return (IPPROTO_DONE);
 #endif
 
@@ -892,6 +900,7 @@ frag6_input(struct mbuf **mp, int *offp, int proto)
 	in6_ifstat_inc(dstifp, ifs6_reass_fail);
 	IP6STAT_INC(ip6s_fragdropped);
 	m_freem(m);
+	*mp = NULL;
 	return (IPPROTO_DONE);
 }
 

sys/netinet6/icmp6.c

@@ -617,8 +617,10 @@ icmp6_input(struct mbuf **mp, int *offp, int proto)
 		 */
 		if ((ip6->ip6_hlim != 1) || (m->m_flags & M_RTALERT_MLD) == 0)
 			goto freeit;
-		if (mld_input(m, off, icmp6len) != 0)
+		if (mld_input(m, off, icmp6len) != 0) {
+			*mp = NULL;
 			return (IPPROTO_DONE);
+		}
 		/* m stays. */
 		break;
 
@@ -853,6 +855,7 @@ icmp6_input(struct mbuf **mp, int *offp, int proto)
 	deliver:
 		if (icmp6_notify_error(&m, off, icmp6len, code) != 0) {
 			/* In this case, m should've been freed. */
+			*mp = NULL;
 			return (IPPROTO_DONE);
 		}
 		break;
@@ -869,11 +872,13 @@ icmp6_input(struct mbuf **mp, int *offp, int proto)
 	/* deliver the packet to appropriate sockets */
 	icmp6_rip6_input(&m, *offp);
 
-	return IPPROTO_DONE;
+	*mp = m;
+	return (IPPROTO_DONE);
 
  freeit:
 	m_freem(m);
-	return IPPROTO_DONE;
+	*mp = NULL;
+	return (IPPROTO_DONE);
 }
 
 static int
@@ -1106,6 +1111,7 @@ icmp6_notify_error(struct mbuf **mp, int off, int icmp6len, int code)
 
   freeit:
 	m_freem(m);
+	*mp = NULL;
 	return (-1);
 }
 
@@ -1918,6 +1924,7 @@ icmp6_rip6_input(struct mbuf **mp, int off)
 	fromsa.sin6_addr = ip6->ip6_src;
 	if (sa6_recoverscope(&fromsa)) {
 		m_freem(m);
+		*mp = NULL;
 		return (IPPROTO_DONE);
 	}
 
@@ -2041,7 +2048,8 @@ icmp6_rip6_input(struct mbuf **mp, int off)
 		m_freem(m);
 		IP6STAT_DEC(ip6s_delivered);
 	}
-	return IPPROTO_DONE;
+	*mp = NULL;
+	return (IPPROTO_DONE);
 }
 
 /*

sys/netinet6/ip6_input.c

@@ -1010,8 +1010,10 @@ ip6_hopopts_input(u_int32_t *plenp, u_int32_t *rtalertp,
 	off += hbhlen;
 	hbhlen -= sizeof(struct ip6_hbh);
 	if (ip6_process_hopopts(m, (u_int8_t *)hbh + sizeof(struct ip6_hbh),
-				hbhlen, rtalertp, plenp) < 0)
+				hbhlen, rtalertp, plenp) < 0) {
+		*mp = NULL;
 		return (-1);
+	}
 
 	*offp = off;
 	*mp = m;

sys/netinet6/route6.c

@@ -110,9 +110,11 @@ route6_input(struct mbuf **mp, int *offp, int proto)
 		IP6STAT_INC(ip6s_badoptions);
 		icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
 			    (caddr_t)&rh->ip6r_type - (caddr_t)ip6);
+		*mp = NULL;
 		return (IPPROTO_DONE);
 	}
 
 	*offp += rhlen;
+	*mp = m;
 	return (rh->ip6r_nxt);
 }

sys/netinet6/udp6_usrreq.c

@@ -394,8 +394,11 @@ udp6_input(struct mbuf **mp, int *offp, int proto)
 						else
 							UDP_PROBE(receive, NULL, last,
 							    ip6, last, uh);
-						if (udp6_append(last, n, off, fromsa))
+						if (udp6_append(last, n, off, fromsa)) {
+							/* XXX-BZ do we leak m here? */
+							*mp = NULL;
 							return (IPPROTO_DONE);
+						}
 					}
 					INP_RUNLOCK(last);
 				}
@@ -434,6 +437,7 @@ udp6_input(struct mbuf **mp, int *offp, int proto)
 				INP_RUNLOCK(last);
 		} else
 			INP_RUNLOCK(last);
+		*mp = NULL;
 		return (IPPROTO_DONE);
 	}
 	/*
@@ -501,6 +505,7 @@ udp6_input(struct mbuf **mp, int *offp, int proto)
 		if (V_udp_blackhole)
 			goto badunlocked;
 		icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOPORT, 0);
+		*mp = NULL;
 		return (IPPROTO_DONE);
 	}
 	INP_RLOCK_ASSERT(inp);
@@ -509,6 +514,7 @@ udp6_input(struct mbuf **mp, int *offp, int proto)
 		if (up->u_rxcslen == 0 || up->u_rxcslen > ulen) {
 			INP_RUNLOCK(inp);
 			m_freem(m);
+			*mp = NULL;
 			return (IPPROTO_DONE);
 		}
 	}
@@ -518,11 +524,13 @@ udp6_input(struct mbuf **mp, int *offp, int proto)
 		UDP_PROBE(receive, NULL, inp, ip6, inp, uh);
 	if (udp6_append(inp, m, off, fromsa) == 0)
 		INP_RUNLOCK(inp);
+	*mp = NULL;
 	return (IPPROTO_DONE);
 
 badunlocked:
 	if (m)
 		m_freem(m);
+	*mp = NULL;
 	return (IPPROTO_DONE);
 }