sctp: validate from_addr_param return

Ilja reported that, simply putting it, nothing was validating that
from_addr_param functions were operating on initialized memory. That is,
the parameter itself was being validated by sctp_walk_params, but it
doesn't check for types and their specific sizes and it could be a 0-length
one, causing from_addr_param to potentially work over the next parameter or
even uninitialized memory.

The fix here is to, in all calls to from_addr_param, check if enough space
is there for the wanted IP address type.
Reported-by: Ilja Van Sprundel <ivansprundel@ioactive.com>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sctp/structs.h

@@ -461,7 +461,7 @@ struct sctp_af {
 					 int saddr);
 	void		(*from_sk)	(union sctp_addr *,
 					 struct sock *sk);
-	void		(*from_addr_param) (union sctp_addr *,
+	bool		(*from_addr_param) (union sctp_addr *,
 					    union sctp_addr_param *,
 					    __be16 port, int iif);
 	int		(*to_addr_param) (const union sctp_addr *,

net/sctp/bind_addr.c

@@ -270,22 +270,19 @@ int sctp_raw_to_bind_addrs(struct sctp_bind_addr *bp, __u8 *raw_addr_list,
 		rawaddr = (union sctp_addr_param *)raw_addr_list;
 
 		af = sctp_get_af_specific(param_type2af(param->type));
-		if (unlikely(!af)) {
+		if (unlikely(!af) ||
+		    !af->from_addr_param(&addr, rawaddr, htons(port), 0)) {
 			retval = -EINVAL;
-			sctp_bind_addr_clean(bp);
-			break;
+			goto out_err;
 		}
 
-		af->from_addr_param(&addr, rawaddr, htons(port), 0);
 		if (sctp_bind_addr_state(bp, &addr) != -1)
 			goto next;
 		retval = sctp_add_bind_addr(bp, &addr, sizeof(addr),
 					    SCTP_ADDR_SRC, gfp);
-		if (retval) {
+		if (retval)
 			/* Can't finish building the list, clean up. */
-			sctp_bind_addr_clean(bp);
-			break;
-		}
+			goto out_err;
 
 next:
 		len = ntohs(param->length);
@@ -294,6 +291,12 @@ int sctp_raw_to_bind_addrs(struct sctp_bind_addr *bp, __u8 *raw_addr_list,
 	}
 
 	return retval;
+
+out_err:
+	if (retval)
+		sctp_bind_addr_clean(bp);
+
+	return retval;
 }
 
 /********************************************************************

net/sctp/input.c

@@ -1131,7 +1131,8 @@ static struct sctp_association *__sctp_rcv_init_lookup(struct net *net,
 		if (!af)
 			continue;
 
-		af->from_addr_param(paddr, params.addr, sh->source, 0);
+		if (!af->from_addr_param(paddr, params.addr, sh->source, 0))
+			continue;
 
 		asoc = __sctp_lookup_association(net, laddr, paddr, transportp);
 		if (asoc)
@@ -1174,7 +1175,8 @@ static struct sctp_association *__sctp_rcv_asconf_lookup(
 	if (unlikely(!af))
 		return NULL;
 
-	af->from_addr_param(&paddr, param, peer_port, 0);
+	if (af->from_addr_param(&paddr, param, peer_port, 0))
+		return NULL;
 
 	return __sctp_lookup_association(net, laddr, &paddr, transportp);
 }

net/sctp/ipv6.c

@@ -551,15 +551,20 @@ static void sctp_v6_to_sk_daddr(union sctp_addr *addr, struct sock *sk)
 }
 
 /* Initialize a sctp_addr from an address parameter. */
-static void sctp_v6_from_addr_param(union sctp_addr *addr,
+static bool sctp_v6_from_addr_param(union sctp_addr *addr,
 				    union sctp_addr_param *param,
 				    __be16 port, int iif)
 {
+	if (ntohs(param->v6.param_hdr.length) < sizeof(struct sctp_ipv6addr_param))
+		return false;
+
 	addr->v6.sin6_family = AF_INET6;
 	addr->v6.sin6_port = port;
 	addr->v6.sin6_flowinfo = 0; /* BUG */
 	addr->v6.sin6_addr = param->v6.addr;
 	addr->v6.sin6_scope_id = iif;
+
+	return true;
 }
 
 /* Initialize an address parameter from a sctp_addr and return the length

net/sctp/protocol.c

@@ -254,14 +254,19 @@ static void sctp_v4_to_sk_daddr(union sctp_addr *addr, struct sock *sk)
 }
 
 /* Initialize a sctp_addr from an address parameter. */
-static void sctp_v4_from_addr_param(union sctp_addr *addr,
+static bool sctp_v4_from_addr_param(union sctp_addr *addr,
 				    union sctp_addr_param *param,
 				    __be16 port, int iif)
 {
+	if (ntohs(param->v4.param_hdr.length) < sizeof(struct sctp_ipv4addr_param))
+		return false;
+
 	addr->v4.sin_family = AF_INET;
 	addr->v4.sin_port = port;
 	addr->v4.sin_addr.s_addr = param->v4.addr.s_addr;
 	memset(addr->v4.sin_zero, 0, sizeof(addr->v4.sin_zero));
+
+	return true;
 }
 
 /* Initialize an address parameter from a sctp_addr and return the length

net/sctp/sm_make_chunk.c

@@ -2346,11 +2346,13 @@ int sctp_process_init(struct sctp_association *asoc, struct sctp_chunk *chunk,
 
 	/* Process the initialization parameters.  */
 	sctp_walk_params(param, peer_init, init_hdr.params) {
-		if (!src_match && (param.p->type == SCTP_PARAM_IPV4_ADDRESS ||
-		    param.p->type == SCTP_PARAM_IPV6_ADDRESS)) {
+		if (!src_match &&
+		    (param.p->type == SCTP_PARAM_IPV4_ADDRESS ||
+		     param.p->type == SCTP_PARAM_IPV6_ADDRESS)) {
 			af = sctp_get_af_specific(param_type2af(param.p->type));
-			af->from_addr_param(&addr, param.addr,
-					    chunk->sctp_hdr->source, 0);
+			if (!af->from_addr_param(&addr, param.addr,
+						 chunk->sctp_hdr->source, 0))
+				continue;
 			if (sctp_cmp_addr_exact(sctp_source(chunk), &addr))
 				src_match = 1;
 		}
@@ -2531,7 +2533,8 @@ static int sctp_process_param(struct sctp_association *asoc,
 			break;
 do_addr_param:
 		af = sctp_get_af_specific(param_type2af(param.p->type));
-		af->from_addr_param(&addr, param.addr, htons(asoc->peer.port), 0);
+		if (!af->from_addr_param(&addr, param.addr, htons(asoc->peer.port), 0))
+			break;
 		scope = sctp_scope(peer_addr);
 		if (sctp_in_scope(net, &addr, scope))
 			if (!sctp_assoc_add_peer(asoc, &addr, gfp, SCTP_UNCONFIRMED))
@@ -2632,15 +2635,13 @@ static int sctp_process_param(struct sctp_association *asoc,
 		addr_param = param.v + sizeof(struct sctp_addip_param);
 
 		af = sctp_get_af_specific(param_type2af(addr_param->p.type));
-		if (af == NULL)
+		if (!af)
 			break;
 
-		af->from_addr_param(&addr, addr_param,
-				    htons(asoc->peer.port), 0);
+		if (!af->from_addr_param(&addr, addr_param,
+					 htons(asoc->peer.port), 0))
+			break;
 
-		/* if the address is invalid, we can't process it.
-		 * XXX: see spec for what to do.
-		 */
 		if (!af->addr_valid(&addr, NULL, NULL))
 			break;
 
@@ -3054,7 +3055,8 @@ static __be16 sctp_process_asconf_param(struct sctp_association *asoc,
 	if (unlikely(!af))
 		return SCTP_ERROR_DNS_FAILED;
 
-	af->from_addr_param(&addr, addr_param, htons(asoc->peer.port), 0);
+	if (!af->from_addr_param(&addr, addr_param, htons(asoc->peer.port), 0))
+		return SCTP_ERROR_DNS_FAILED;
 
 	/* ADDIP 4.2.1  This parameter MUST NOT contain a broadcast
 	 * or multicast address.
@@ -3331,7 +3333,8 @@ static void sctp_asconf_param_success(struct sctp_association *asoc,
 
 	/* We have checked the packet before, so we do not check again.	*/
 	af = sctp_get_af_specific(param_type2af(addr_param->p.type));
-	af->from_addr_param(&addr, addr_param, htons(bp->port), 0);
+	if (!af->from_addr_param(&addr, addr_param, htons(bp->port), 0))
+		return;
 
 	switch (asconf_param->param_hdr.type) {
 	case SCTP_PARAM_ADD_IP: