inet: fix addr_len/msg->msg_namelen assignment in recv_error and rxpmtu functions

Commit bceaa902 ("inet: prevent leakage
of uninitialized memory to user in recv syscalls") conditionally updated
addr_len if the msg_name is written to. The recv_error and rxpmtu
functions relied on the recvmsg functions to set up addr_len before.

As this does not happen any more we have to pass addr_len to those
functions as well and set it to the size of the corresponding sockaddr
length.

This broke traceroute and such.

Fixes: bceaa902 ("inet: prevent leakage of uninitialized memory to user in recv syscalls")
Reported-by: Brad Spengler <spender@grsecurity.net>
Reported-by: Tom Labanowski
Cc: mpb <mpb.mail@gmail.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ip.h

@@ -473,7 +473,7 @@ int compat_ip_getsockopt(struct sock *sk, int level, int optname,
 int ip_ra_control(struct sock *sk, unsigned char on,
 		  void (*destructor)(struct sock *));
 
-int ip_recv_error(struct sock *sk, struct msghdr *msg, int len);
+int ip_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len);
 void ip_icmp_error(struct sock *sk, struct sk_buff *skb, int err, __be16 port,
 		   u32 info, u8 *payload);
 void ip_local_error(struct sock *sk, int err, __be32 daddr, __be16 dport,

include/net/ipv6.h

@@ -776,8 +776,10 @@ int compat_ipv6_getsockopt(struct sock *sk, int level, int optname,
 
 int ip6_datagram_connect(struct sock *sk, struct sockaddr *addr, int addr_len);
 
-int ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len);
-int ipv6_recv_rxpmtu(struct sock *sk, struct msghdr *msg, int len);
+int ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len,
+		    int *addr_len);
+int ipv6_recv_rxpmtu(struct sock *sk, struct msghdr *msg, int len,
+		     int *addr_len);
 void ipv6_icmp_error(struct sock *sk, struct sk_buff *skb, int err, __be16 port,
 		     u32 info, u8 *payload);
 void ipv6_local_error(struct sock *sk, int err, struct flowi6 *fl6, u32 info);

include/net/ping.h

@@ -31,7 +31,8 @@
 
 /* Compatibility glue so we can support IPv6 when it's compiled as a module */
 struct pingv6_ops {
-	int (*ipv6_recv_error)(struct sock *sk, struct msghdr *msg, int len);
+	int (*ipv6_recv_error)(struct sock *sk, struct msghdr *msg, int len,
+			       int *addr_len);
 	int (*ip6_datagram_recv_ctl)(struct sock *sk, struct msghdr *msg,
 				     struct sk_buff *skb);
 	int (*icmpv6_err_convert)(u8 type, u8 code, int *err);

net/ipv4/ip_sockglue.c

@@ -386,7 +386,7 @@ void ip_local_error(struct sock *sk, int err, __be32 daddr, __be16 port, u32 inf
 /*
  *	Handle MSG_ERRQUEUE
  */
-int ip_recv_error(struct sock *sk, struct msghdr *msg, int len)
+int ip_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len)
 {
 	struct sock_exterr_skb *serr;
 	struct sk_buff *skb, *skb2;
@@ -423,6 +423,7 @@ int ip_recv_error(struct sock *sk, struct msghdr *msg, int len)
 						   serr->addr_offset);
 		sin->sin_port = serr->port;
 		memset(&sin->sin_zero, 0, sizeof(sin->sin_zero));
+		*addr_len = sizeof(*sin);
 	}
 
 	memcpy(&errhdr.ee, &serr->ee, sizeof(struct sock_extended_err));

net/ipv4/ping.c

@@ -841,10 +841,11 @@ int ping_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 
 	if (flags & MSG_ERRQUEUE) {
 		if (family == AF_INET) {
-			return ip_recv_error(sk, msg, len);
+			return ip_recv_error(sk, msg, len, addr_len);
 #if IS_ENABLED(CONFIG_IPV6)
 		} else if (family == AF_INET6) {
-			return pingv6_ops.ipv6_recv_error(sk, msg, len);
+			return pingv6_ops.ipv6_recv_error(sk, msg, len,
+							  addr_len);
 #endif
 		}
 	}

net/ipv4/raw.c

@@ -697,7 +697,7 @@ static int raw_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 		goto out;
 
 	if (flags & MSG_ERRQUEUE) {
-		err = ip_recv_error(sk, msg, len);
+		err = ip_recv_error(sk, msg, len, addr_len);
 		goto out;
 	}
 

net/ipv4/udp.c

@@ -1236,7 +1236,7 @@ int udp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 	bool slow;
 
 	if (flags & MSG_ERRQUEUE)
-		return ip_recv_error(sk, msg, len);
+		return ip_recv_error(sk, msg, len, addr_len);
 
 try_again:
 	skb = __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0),

net/ipv6/datagram.c

@@ -318,7 +318,7 @@ void ipv6_local_rxpmtu(struct sock *sk, struct flowi6 *fl6, u32 mtu)
 /*
  *	Handle MSG_ERRQUEUE
  */
-int ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len)
+int ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len)
 {
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct sock_exterr_skb *serr;
@@ -369,6 +369,7 @@ int ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len)
 					       &sin->sin6_addr);
 			sin->sin6_scope_id = 0;
 		}
+		*addr_len = sizeof(*sin);
 	}
 
 	memcpy(&errhdr.ee, &serr->ee, sizeof(struct sock_extended_err));
@@ -423,7 +424,8 @@ EXPORT_SYMBOL_GPL(ipv6_recv_error);
 /*
  *	Handle IPV6_RECVPATHMTU
  */
-int ipv6_recv_rxpmtu(struct sock *sk, struct msghdr *msg, int len)
+int ipv6_recv_rxpmtu(struct sock *sk, struct msghdr *msg, int len,
+		     int *addr_len)
 {
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct sk_buff *skb;
@@ -457,6 +459,7 @@ int ipv6_recv_rxpmtu(struct sock *sk, struct msghdr *msg, int len)
 		sin->sin6_port = 0;
 		sin->sin6_scope_id = mtu_info.ip6m_addr.sin6_scope_id;
 		sin->sin6_addr = mtu_info.ip6m_addr.sin6_addr;
+		*addr_len = sizeof(*sin);
 	}
 
 	put_cmsg(msg, SOL_IPV6, IPV6_PATHMTU, sizeof(mtu_info), &mtu_info);

net/ipv6/ping.c

@@ -57,7 +57,8 @@ static struct inet_protosw pingv6_protosw = {
 
 
 /* Compatibility glue so we can support IPv6 when it's compiled as a module */
-static int dummy_ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len)
+static int dummy_ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len,
+				 int *addr_len)
 {
 	return -EAFNOSUPPORT;
 }

net/ipv6/raw.c

@@ -466,10 +466,10 @@ static int rawv6_recvmsg(struct kiocb *iocb, struct sock *sk,
 		return -EOPNOTSUPP;
 
 	if (flags & MSG_ERRQUEUE)
-		return ipv6_recv_error(sk, msg, len);
+		return ipv6_recv_error(sk, msg, len, addr_len);
 
 	if (np->rxpmtu && np->rxopt.bits.rxpmtu)
-		return ipv6_recv_rxpmtu(sk, msg, len);
+		return ipv6_recv_rxpmtu(sk, msg, len, addr_len);
 
 	skb = skb_recv_datagram(sk, flags, noblock, &err);
 	if (!skb)

net/ipv6/udp.c

@@ -393,10 +393,10 @@ int udpv6_recvmsg(struct kiocb *iocb, struct sock *sk,
 	bool slow;
 
 	if (flags & MSG_ERRQUEUE)
-		return ipv6_recv_error(sk, msg, len);
+		return ipv6_recv_error(sk, msg, len, addr_len);
 
 	if (np->rxpmtu && np->rxopt.bits.rxpmtu)
-		return ipv6_recv_rxpmtu(sk, msg, len);
+		return ipv6_recv_rxpmtu(sk, msg, len, addr_len);
 
 try_again:
 	skb = __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0),

net/l2tp/l2tp_ip6.c

@@ -665,7 +665,7 @@ static int l2tp_ip6_recvmsg(struct kiocb *iocb, struct sock *sk,
 		*addr_len = sizeof(*lsa);
 
 	if (flags & MSG_ERRQUEUE)
-		return ipv6_recv_error(sk, msg, len);
+		return ipv6_recv_error(sk, msg, len, addr_len);
 
 	skb = skb_recv_datagram(sk, flags, noblock, &err);
 	if (!skb)