CVE-2013-7271: Improper Input Validation (CWE-20)
value: The x25_recvmsg function in net/x25/af_x25.c in the Linux kernel before 3.12.4 updates a certain length value without ensuring that an associated data structure has been initialized, which allows local users to obtain sensitive information from kernel memory via a (1) recvfrom, (2) recvmmsg, or (3) recvmsg system call.
CWE description: The product receives input or data, but it does
        not validate or incorrectly validates that the input has the
        properties that are required to process the data safely and
        correctly.
Published: 2014-01-06T16:55Z
Repository: https://github.com/torvalds/linux
Language: C
Files changed: crypto/algif_hash.c, crypto/algif_skcipher.c, drivers/isdn/mISDN/socket.c, drivers/net/ppp/pppoe.c, include/linux/net.h, net/appletalk/ddp.c, net/atm/common.c, net/ax25/af_ax25.c, net/bluetooth/af_bluetooth.c, net/bluetooth/hci_sock.c, net/bluetooth/rfcomm/sock.c, net/bluetooth/sco.c, net/caif/caif_socket.c, net/compat.c, net/core/iovec.c, net/ipx/af_ipx.c, net/irda/af_irda.c, net/iucv/af_iucv.c, net/key/af_key.c, net/l2tp/l2tp_ppp.c, net/llc/af_llc.c, net/netlink/af_netlink.c, net/netrom/af_netrom.c, net/nfc/llcp_sock.c, net/nfc/rawsock.c, net/packet/af_packet.c, net/rds/recv.c, net/rose/af_rose.c, net/rxrpc/ar-recvmsg.c, net/socket.c, net/tipc/socket.c, net/unix/af_unix.c, net/vmw_vsock/af_vsock.c, net/vmw_vsock/vmci_transport.c, net/x25/af_x25.c
Commit date: 2013-11-20 21:52:30 -0500
Commit message: net: rework recvmsg handler msg_name and msg_namelen logic

This patch now always passes msg->msg_namelen as 0. recvmsg handlers must
set msg_namelen to the proper size <= sizeof(struct sockaddr_storage)
to return msg_name to the user.

This prevents numerous uninitialized memory leaks we had in the
recvmsg handlers and makes it harder for new code to accidentally leak
uninitialized memory.

Optimize for the case recvfrom is called with NULL as address. We don't
need to copy the address at all, so set it to NULL before invoking the
recvmsg handler. We can do so, because all the recvmsg handlers must
cope with the case a plain read() is called on them. read() also sets
msg_name to NULL.

Also document these changes in include/linux/net.h as suggested by David
Miller.

Changes since RFC:

Set msg->msg_name = NULL if user specified a NULL in msg_name but had a
non-null msg_namelen in verify_iovec/verify_compat_iovec. This doesn't
affect sendto as it would bail out earlier while trying to copy-in the
address. It also more naturally reflects the logic by the callers of
verify_iovec.

With this change in place I could remove "
if (!uaddr || msg_sys->msg_namelen == 0)
	msg->msg_name = NULL
".

This change does not alter the user visible error logic as we ignore
msg_namelen as long as msg_name is NULL.

Also remove two unnecessary curly brackets in ___sys_recvmsg and change
comments to netdev style.

Cc: David Miller <davem@davemloft.net>
Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Diff: diff --git a/crypto/algif_hash.c b/crypto/algif_hash.c
index 0262210cad386b..ef5356cd280a54 100644
--- a/crypto/algif_hash.c
+++ b/crypto/algif_hash.c
@@ -159,12 +159,10 @@ static int hash_recvmsg(struct kiocb *unused, struct socket *sock,
 	if (len > ds)
 		len = ds;
 	else if (len < ds)
 		msg->msg_flags |= MSG_TRUNC;
 
-	msg->msg_namelen = 0;
-
 	lock_sock(sk);
 	if (ctx->more) {
 		ctx->more = 0;
 		ahash_request_set_crypt(&ctx->req, NULL, ctx->result, 0);
 		err = af_alg_wait_for_completion(crypto_ahash_final(&ctx->req),
diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c
index a1c4f0a5558320..6a6dfc062d2a47 100644
--- a/crypto/algif_skcipher.c
+++ b/crypto/algif_skcipher.c
@@ -430,11 +430,10 @@ static int skcipher_recvmsg(struct kiocb *unused, struct socket *sock,
 	int err = -EAGAIN;
 	int used;
 	long copied = 0;
 
 	lock_sock(sk);
-	msg->msg_namelen = 0;
 	for (iov = msg->msg_iov, iovlen = msg->msg_iovlen; iovlen > 0;
 	     iovlen--, iov++) {
 		unsigned long seglen = iov->iov_len;
 		char __user *from = iov->iov_base;
 
diff --git a/drivers/isdn/mISDN/socket.c b/drivers/isdn/mISDN/socket.c
index e47dcb9d1e91d0..5cefb479c70723 100644
--- a/drivers/isdn/mISDN/socket.c
+++ b/drivers/isdn/mISDN/socket.c
@@ -115,11 +115,10 @@ static int
 mISDN_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 		   struct msghdr *msg, size_t len, int flags)
 {
 	struct sk_buff		*skb;
 	struct sock		*sk = sock->sk;
-	struct sockaddr_mISDN	*maddr;
 
 	int		copied, err;
 
 	if (*debug & DEBUG_SOCKET)
 		printk(KERN_DEBUG "%s: len %d, flags %x ch.nr %d, proto %x\n",
@@ -133,13 +132,13 @@ mISDN_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 
 	skb = skb_recv_datagram(sk, flags, flags & MSG_DONTWAIT, &err);
 	if (!skb)
 		return err;
 
-	if (msg->msg_namelen >= sizeof(struct sockaddr_mISDN)) {
-		msg->msg_namelen = sizeof(struct sockaddr_mISDN);
-		maddr = (struct sockaddr_mISDN *)msg->msg_name;
+	if (msg->msg_name) {
+		struct sockaddr_mISDN *maddr = msg->msg_name;
+
 		maddr->family = AF_ISDN;
 		maddr->dev = _pms(sk)->dev->id;
 		if ((sk->sk_protocol == ISDN_P_LAPD_TE) ||
 		    (sk->sk_protocol == ISDN_P_LAPD_NT)) {
 			maddr->channel = (mISDN_HEAD_ID(skb) >> 16) & 0xff;
@@ -148,15 +147,11 @@ mISDN_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 		} else {
 			maddr->channel = _pms(sk)->ch.nr;
 			maddr->sapi = _pms(sk)->ch.addr & 0xFF;
 			maddr->tei =  (_pms(sk)->ch.addr >> 8) & 0xFF;
 		}
-	} else {
-		if (msg->msg_namelen)
-			printk(KERN_WARNING "%s: too small namelen %d\n",
-			       __func__, msg->msg_namelen);
-		msg->msg_namelen = 0;
+		msg->msg_namelen = sizeof(*maddr);
 	}
 
 	copied = skb->len + MISDN_HEADER_LEN;
 	if (len < copied) {
 		if (flags & MSG_PEEK)
diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c
index 5f66e30d982396..82ee6ed954cb84 100644
--- a/drivers/net/ppp/pppoe.c
+++ b/drivers/net/ppp/pppoe.c
@@ -977,12 +977,10 @@ static int pppoe_recvmsg(struct kiocb *iocb, struct socket *sock,
 	skb = skb_recv_datagram(sk, flags & ~MSG_DONTWAIT,
 				flags & MSG_DONTWAIT, &error);
 	if (error < 0)
 		goto end;
 
-	m->msg_namelen = 0;
-
 	if (skb) {
 		total_len = min_t(size_t, total_len, skb->len);
 		error = skb_copy_datagram_iovec(skb, 0, m->msg_iov, total_len);
 		if (error == 0) {
 			consume_skb(skb);
diff --git a/include/linux/net.h b/include/linux/net.h
index b292a04355717a..4bcee94cef9314 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -162,10 +162,18 @@ struct proto_ops {
 	int		(*compat_getsockopt)(struct socket *sock, int level,
 				      int optname, char __user *optval, int __user *optlen);
 #endif
 	int		(*sendmsg)   (struct kiocb *iocb, struct socket *sock,
 				      struct msghdr *m, size_t total_len);
+	/* Notes for implementing recvmsg:
+	 * ===============================
+	 * msg->msg_namelen should get updated by the recvmsg handlers
+	 * iff msg_name != NULL. It is by default 0 to prevent
+	 * returning uninitialized memory to user space.  The recvfrom
+	 * handlers can assume that msg.msg_name is either NULL or has
+	 * a minimum size of sizeof(struct sockaddr_storage).
+	 */
 	int		(*recvmsg)   (struct kiocb *iocb, struct socket *sock,
 				      struct msghdr *m, size_t total_len,
 				      int flags);
 	int		(*mmap)	     (struct file *file, struct socket *sock,
 				      struct vm_area_struct * vma);
diff --git a/net/appletalk/ddp.c b/net/appletalk/ddp.c
index 7fee50d637f956..7d424ac6e760bb 100644
--- a/net/appletalk/ddp.c
+++ b/net/appletalk/ddp.c
@@ -1733,11 +1733,10 @@ static int atalk_sendmsg(struct kiocb *iocb, struct socket *sock, struct msghdr
 
 static int atalk_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg,
 			 size_t size, int flags)
 {
 	struct sock *sk = sock->sk;
-	struct sockaddr_at *sat = (struct sockaddr_at *)msg->msg_name;
 	struct ddpehdr *ddp;
 	int copied = 0;
 	int offset = 0;
 	int err = 0;
 	struct sk_buff *skb;
@@ -1762,18 +1761,17 @@ static int atalk_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr
 		copied = size;
 		msg->msg_flags |= MSG_TRUNC;
 	}
 	err = skb_copy_datagram_iovec(skb, offset, msg->msg_iov, copied);
 
-	if (!err) {
-		if (sat) {
-			sat->sat_family      = AF_APPLETALK;
-			sat->sat_port        = ddp->deh_sport;
-			sat->sat_addr.s_node = ddp->deh_snode;
-			sat->sat_addr.s_net  = ddp->deh_snet;
-		}
-		msg->msg_namelen = sizeof(*sat);
+	if (!err && msg->msg_name) {
+		struct sockaddr_at *sat = msg->msg_name;
+		sat->sat_family      = AF_APPLETALK;
+		sat->sat_port        = ddp->deh_sport;
+		sat->sat_addr.s_node = ddp->deh_snode;
+		sat->sat_addr.s_net  = ddp->deh_snet;
+		msg->msg_namelen     = sizeof(*sat);
 	}
 
 	skb_free_datagram(sk, skb);	/* Free the datagram. */
 
 out:
diff --git a/net/atm/common.c b/net/atm/common.c
index 737bef59ce899a..7b491006eaf400 100644
--- a/net/atm/common.c
+++ b/net/atm/common.c
@@ -529,12 +529,10 @@ int vcc_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg,
 	struct sock *sk = sock->sk;
 	struct atm_vcc *vcc;
 	struct sk_buff *skb;
 	int copied, error = -EINVAL;
 
-	msg->msg_namelen = 0;
-
 	if (sock->state != SS_CONNECTED)
 		return -ENOTCONN;
 
 	/* only handle MSG_DONTWAIT and MSG_PEEK */
 	if (flags & ~(MSG_DONTWAIT | MSG_PEEK))
diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
index a00123ebb0ae07..7bb1605bdfd999 100644
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -1634,15 +1634,15 @@ static int ax25_recvmsg(struct kiocb *iocb, struct socket *sock,
 		msg->msg_flags |= MSG_TRUNC;
 	}
 
 	skb_copy_datagram_iovec(skb, 0, msg->msg_iov, copied);
 
-	if (msg->msg_namelen != 0) {
-		struct sockaddr_ax25 *sax = (struct sockaddr_ax25 *)msg->msg_name;
+	if (msg->msg_name) {
 		ax25_digi digi;
 		ax25_address src;
 		const unsigned char *mac = skb_mac_header(skb);
+		struct sockaddr_ax25 *sax = msg->msg_name;
 
 		memset(sax, 0, sizeof(struct full_sockaddr_ax25));
 		ax25_addr_parse(mac + 1, skb->data - mac - 1, &src, NULL,
 				&digi, NULL, NULL);
 		sax->sax25_family = AF_AX25;
diff --git a/net/bluetooth/af_bluetooth.c b/net/bluetooth/af_bluetooth.c
index f6a1671ea2ff79..56ca494621c66e 100644
--- a/net/bluetooth/af_bluetooth.c
+++ b/net/bluetooth/af_bluetooth.c
@@ -222,14 +222,13 @@ int bt_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 	if (flags & (MSG_OOB))
 		return -EOPNOTSUPP;
 
 	skb = skb_recv_datagram(sk, flags, noblock, &err);
 	if (!skb) {
-		if (sk->sk_shutdown & RCV_SHUTDOWN) {
-			msg->msg_namelen = 0;
+		if (sk->sk_shutdown & RCV_SHUTDOWN)
 			return 0;
-		}
+
 		return err;
 	}
 
 	copied = skb->len;
 	if (len < copied) {
@@ -243,12 +242,10 @@ int bt_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 		sock_recv_ts_and_drops(msg, sk, skb);
 
 		if (bt_sk(sk)->skb_msg_name)
 			bt_sk(sk)->skb_msg_name(skb, msg->msg_name,
 						&msg->msg_namelen);
-		else
-			msg->msg_namelen = 0;
 	}
 
 	skb_free_datagram(sk, skb);
 
 	return err ? : copied;
@@ -293,12 +290,10 @@ int bt_sock_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
 	long timeo;
 
 	if (flags & MSG_OOB)
 		return -EOPNOTSUPP;
 
-	msg->msg_namelen = 0;
-
 	BT_DBG("sk %p size %zu", sk, size);
 
 	lock_sock(sk);
 
 	target = sock_rcvlowat(sk, flags & MSG_WAITALL, size);
diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c
index 71f0be1730801a..6a6c8bb4fd72d4 100644
--- a/net/bluetooth/hci_sock.c
+++ b/net/bluetooth/hci_sock.c
@@ -854,12 +854,10 @@ static int hci_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 
 	skb = skb_recv_datagram(sk, flags, noblock, &err);
 	if (!skb)
 		return err;
 
-	msg->msg_namelen = 0;
-
 	copied = skb->len;
 	if (len < copied) {
 		msg->msg_flags |= MSG_TRUNC;
 		copied = len;
 	}
diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c
index c4d3d423f89b84..c80766f892c36e 100644
--- a/net/bluetooth/rfcomm/sock.c
+++ b/net/bluetooth/rfcomm/sock.c
@@ -613,11 +613,10 @@ static int rfcomm_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 	struct rfcomm_dlc *d = rfcomm_pi(sk)->dlc;
 	int len;
 
 	if (test_and_clear_bit(RFCOMM_DEFER_SETUP, &d->flags)) {
 		rfcomm_dlc_accept(d);
-		msg->msg_namelen = 0;
 		return 0;
 	}
 
 	len = bt_sock_stream_recvmsg(iocb, sock, msg, size, flags);
 
diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c
index 12a0e51e21e136..24fa3964b3c84d 100644
--- a/net/bluetooth/sco.c
+++ b/net/bluetooth/sco.c
@@ -709,11 +709,10 @@ static int sco_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 
 	if (sk->sk_state == BT_CONNECT2 &&
 	    test_bit(BT_SK_DEFER_SETUP, &bt_sk(sk)->flags)) {
 		sco_conn_defer_accept(pi->conn->hcon, pi->setting);
 		sk->sk_state = BT_CONFIG;
-		msg->msg_namelen = 0;
 
 		release_sock(sk);
 		return 0;
 	}
 
diff --git a/net/caif/caif_socket.c b/net/caif/caif_socket.c
index 05a41c7ec304e4..d6be3edb7a4349 100644
--- a/net/caif/caif_socket.c
+++ b/net/caif/caif_socket.c
@@ -284,12 +284,10 @@ static int caif_seqpkt_recvmsg(struct kiocb *iocb, struct socket *sock,
 
 	ret = -EOPNOTSUPP;
 	if (m->msg_flags&MSG_OOB)
 		goto read_error;
 
-	m->msg_namelen = 0;
-
 	skb = skb_recv_datagram(sk, flags, 0 , &ret);
 	if (!skb)
 		goto read_error;
 	copylen = skb->len;
 	if (len < copylen) {
@@ -359,12 +357,10 @@ static int caif_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
 
 	err = -EOPNOTSUPP;
 	if (flags&MSG_OOB)
 		goto out;
 
-	msg->msg_namelen = 0;
-
 	/*
 	 * Lock the socket to prevent queue disordering
 	 * while sleeps in memcpy_tomsg
 	 */
 	err = -EAGAIN;
diff --git a/net/compat.c b/net/compat.c
index 89032580bd1d8a..618c6a8a911b65 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -91,11 +91,12 @@ int verify_compat_iovec(struct msghdr *kern_msg, struct iovec *kern_iov,
 						      kern_msg->msg_namelen,
 						      kern_address);
 			if (err < 0)
 				return err;
 		}
-		kern_msg->msg_name = kern_address;
+		if (kern_msg->msg_name)
+			kern_msg->msg_name = kern_address;
 	} else
 		kern_msg->msg_name = NULL;
 
 	tot_len = iov_from_user_compat_to_kern(kern_iov,
 					  (struct compat_iovec __user *)kern_msg->msg_iov,
diff --git a/net/core/iovec.c b/net/core/iovec.c
index 4cdb7c48dad6cb..b61869429f4ced 100644
--- a/net/core/iovec.c
+++ b/net/core/iovec.c
@@ -46,11 +46,12 @@ int verify_iovec(struct msghdr *m, struct iovec *iov, struct sockaddr_storage *a
 			err = move_addr_to_kernel(namep, m->msg_namelen,
 						  address);
 			if (err < 0)
 				return err;
 		}
-		m->msg_name = address;
+		if (m->msg_name)
+			m->msg_name = address;
 	} else {
 		m->msg_name = NULL;
 	}
 
 	size = m->msg_iovlen * sizeof(struct iovec);
diff --git a/net/ipx/af_ipx.c b/net/ipx/af_ipx.c
index 7a1e0fc1bd4dd2..e096025b477f39 100644
--- a/net/ipx/af_ipx.c
+++ b/net/ipx/af_ipx.c
@@ -1821,19 +1821,18 @@ static int ipx_recvmsg(struct kiocb *iocb, struct socket *sock,
 	if (rc)
 		goto out_free;
 	if (skb->tstamp.tv64)
 		sk->sk_stamp = skb->tstamp;
 
-	msg->msg_namelen = sizeof(*sipx);
-
 	if (sipx) {
 		sipx->sipx_family	= AF_IPX;
 		sipx->sipx_port		= ipx->ipx_source.sock;
 		memcpy(sipx->sipx_node, ipx->ipx_source.node, IPX_NODE_LEN);
 		sipx->sipx_network	= IPX_SKB_CB(skb)->ipx_source_net;
 		sipx->sipx_type 	= ipx->ipx_type;
 		sipx->sipx_zero		= 0;
+		msg->msg_namelen	= sizeof(*sipx);
 	}
 	rc = copied;
 
 out_free:
 	skb_free_datagram(sk, skb);
diff --git a/net/irda/af_irda.c b/net/irda/af_irda.c
index 0f676908d15b61..de7db23049f141 100644
--- a/net/irda/af_irda.c
+++ b/net/irda/af_irda.c
@@ -1383,12 +1383,10 @@ static int irda_recvmsg_dgram(struct kiocb *iocb, struct socket *sock,
 	size_t copied;
 	int err;
 
 	IRDA_DEBUG(4, "%s()\n", __func__);
 
-	msg->msg_namelen = 0;
-
 	skb = skb_recv_datagram(sk, flags & ~MSG_DONTWAIT,
 				flags & MSG_DONTWAIT, &err);
 	if (!skb)
 		return err;
 
@@ -1449,12 +1447,10 @@ static int irda_recvmsg_stream(struct kiocb *iocb, struct socket *sock,
 
 	err = 0;
 	target = sock_rcvlowat(sk, flags & MSG_WAITALL, size);
 	timeo = sock_rcvtimeo(sk, noblock);
 
-	msg->msg_namelen = 0;
-
 	do {
 		int chunk;
 		struct sk_buff *skb = skb_dequeue(&sk->sk_receive_queue);
 
 		if (skb == NULL) {
diff --git a/net/iucv/af_iucv.c b/net/iucv/af_iucv.c
index 168aff5e60de52..c4b7218058b648 100644
--- a/net/iucv/af_iucv.c
+++ b/net/iucv/af_iucv.c
@@ -1322,12 +1322,10 @@ static int iucv_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 	unsigned int copied, rlen;
 	struct sk_buff *skb, *rskb, *cskb;
 	int err = 0;
 	u32 offset;
 
-	msg->msg_namelen = 0;
-
 	if ((sk->sk_state == IUCV_DISCONN) &&
 	    skb_queue_empty(&iucv->backlog_skb_q) &&
 	    skb_queue_empty(&sk->sk_receive_queue) &&
 	    list_empty(&iucv->message_q.list))
 		return 0;
diff --git a/net/key/af_key.c b/net/key/af_key.c
index 911ef03bf8fbf1..545f047868ad86 100644
--- a/net/key/af_key.c
+++ b/net/key/af_key.c
@@ -3614,11 +3614,10 @@ static int pfkey_recvmsg(struct kiocb *kiocb,
 
 	err = -EINVAL;
 	if (flags & ~(MSG_PEEK|MSG_DONTWAIT|MSG_TRUNC|MSG_CMSG_COMPAT))
 		goto out;
 
-	msg->msg_namelen = 0;
 	skb = skb_recv_datagram(sk, flags, flags & MSG_DONTWAIT, &err);
 	if (skb == NULL)
 		goto out;
 
 	copied = skb->len;
diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
index ffda81ef1a709d..be5fadf3473946 100644
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -195,12 +195,10 @@ static int pppol2tp_recvmsg(struct kiocb *iocb, struct socket *sock,
 
 	err = -EIO;
 	if (sk->sk_state & PPPOX_BOUND)
 		goto end;
 
-	msg->msg_namelen = 0;
-
 	err = 0;
 	skb = skb_recv_datagram(sk, flags & ~MSG_DONTWAIT,
 				flags & MSG_DONTWAIT, &err);
 	if (!skb)
 		goto end;
diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c
index 6cba486353e8a3..7b01b9f5846c84 100644
--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -718,12 +718,10 @@ static int llc_ui_recvmsg(struct kiocb *iocb, struct socket *sock,
 	u32 *seq;
 	unsigned long used;
 	int target;	/* Read at least this many bytes */
 	long timeo;
 
-	msg->msg_namelen = 0;
-
 	lock_sock(sk);
 	copied = -ENOTCONN;
 	if (unlikely(sk->sk_type == SOCK_STREAM && sk->sk_state == TCP_LISTEN))
 		goto out;
 
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index f0176e1a5a81a0..bca50b95c18230 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2333,12 +2333,10 @@ static int netlink_recvmsg(struct kiocb *kiocb, struct socket *sock,
 		if (flags & MSG_CMSG_COMPAT)
 			data_skb = skb_shinfo(skb)->frag_list;
 	}
 #endif
 
-	msg->msg_namelen = 0;
-
 	copied = data_skb->len;
 	if (len < copied) {
 		msg->msg_flags |= MSG_TRUNC;
 		copied = len;
 	}
diff --git a/net/netrom/af_netrom.c b/net/netrom/af_netrom.c
index 698814bfa7adfd..53c19a35fc6dcc 100644
--- a/net/netrom/af_netrom.c
+++ b/net/netrom/af_netrom.c
@@ -1177,14 +1177,13 @@ static int nr_recvmsg(struct kiocb *iocb, struct socket *sock,
 	if (sax != NULL) {
 		memset(sax, 0, sizeof(*sax));
 		sax->sax25_family = AF_NETROM;
 		skb_copy_from_linear_data_offset(skb, 7, sax->sax25_call.ax25_call,
 			      AX25_ADDR_LEN);
+		msg->msg_namelen = sizeof(*sax);
 	}
 
-	msg->msg_namelen = sizeof(*sax);
-
 	skb_free_datagram(sk, skb);
 
 	release_sock(sk);
 	return copied;
 }
diff --git a/net/nfc/llcp_sock.c b/net/nfc/llcp_sock.c
index d308402b67d80c..824c6056bf823b 100644
--- a/net/nfc/llcp_sock.c
+++ b/net/nfc/llcp_sock.c
@@ -805,12 +805,10 @@ static int llcp_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 	struct sk_buff *skb, *cskb;
 	int err = 0;
 
 	pr_debug("%p %zu\n", sk, len);
 
-	msg->msg_namelen = 0;
-
 	lock_sock(sk);
 
 	if (sk->sk_state == LLCP_CLOSED &&
 	    skb_queue_empty(&sk->sk_receive_queue)) {
 		release_sock(sk);
diff --git a/net/nfc/rawsock.c b/net/nfc/rawsock.c
index cd958b381f9615..66bcd2eb577374 100644
--- a/net/nfc/rawsock.c
+++ b/net/nfc/rawsock.c
@@ -242,12 +242,10 @@ static int rawsock_recvmsg(struct kiocb *iocb, struct socket *sock,
 
 	skb = skb_recv_datagram(sk, flags, noblock, &rc);
 	if (!skb)
 		return rc;
 
-	msg->msg_namelen = 0;
-
 	copied = skb->len;
 	if (len < copied) {
 		msg->msg_flags |= MSG_TRUNC;
 		copied = len;
 	}
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 2e8286b47c28e5..61bd50adead1cc 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2658,11 +2658,10 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
 			  struct msghdr *msg, size_t len, int flags)
 {
 	struct sock *sk = sock->sk;
 	struct sk_buff *skb;
 	int copied, err;
-	struct sockaddr_ll *sll;
 	int vnet_hdr_len = 0;
 
 	err = -EINVAL;
 	if (flags & ~(MSG_PEEK|MSG_DONTWAIT|MSG_TRUNC|MSG_CMSG_COMPAT|MSG_ERRQUEUE))
 		goto out;
@@ -2742,26 +2741,14 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
 				     vnet_hdr_len);
 		if (err < 0)
 			goto out_free;
 	}
 
-	/*
-	 *	If the address length field is there to be filled in, we fill
-	 *	it in now.
-	 */
-
-	sll = &PACKET_SKB_CB(skb)->sa.ll;
-	if (sock->type == SOCK_PACKET)
-		msg->msg_namelen = sizeof(struct sockaddr_pkt);
-	else
-		msg->msg_namelen = sll->sll_halen + offsetof(struct sockaddr_ll, sll_addr);
-
-	/*
-	 *	You lose any data beyond the buffer you gave. If it worries a
-	 *	user program they can ask the device for its MTU anyway.
+	/* You lose any data beyond the buffer you gave. If it worries
+	 * a user program they can ask the device for its MTU
+	 * anyway.
 	 */
-
 	copied = skb->len;
 	if (copied > len) {
 		copied = len;
 		msg->msg_flags |= MSG_TRUNC;
 	}
@@ -2770,13 +2757,24 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
 	if (err)
 		goto out_free;
 
 	sock_recv_ts_and_drops(msg, sk, skb);
 
-	if (msg->msg_name)
+	if (msg->msg_name) {
+		/* If the address length field is there to be filled
+		 * in, we fill it in now.
+		 */
+		if (sock->type == SOCK_PACKET) {
+			msg->msg_namelen = sizeof(struct sockaddr_pkt);
+		} else {
+			struct sockaddr_ll *sll = &PACKET_SKB_CB(skb)->sa.ll;
+			msg->msg_namelen = sll->sll_halen +
+				offsetof(struct sockaddr_ll, sll_addr);
+		}
 		memcpy(msg->msg_name, &PACKET_SKB_CB(skb)->sa,
 		       msg->msg_namelen);
+	}
 
 	if (pkt_sk(sk)->auxdata) {
 		struct tpacket_auxdata aux;
 
 		aux.tp_status = TP_STATUS_USER;
diff --git a/net/rds/recv.c b/net/rds/recv.c
index 9f0f17cf6bf9b1..de339b24ca140f 100644
--- a/net/rds/recv.c
+++ b/net/rds/recv.c
@@ -408,12 +408,10 @@ int rds_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg,
 	/* udp_recvmsg()->sock_recvtimeo() gets away without locking too.. */
 	timeo = sock_rcvtimeo(sk, nonblock);
 
 	rdsdebug("size %zu flags 0x%x timeo %ld\n", size, msg_flags, timeo);
 
-	msg->msg_namelen = 0;
-
 	if (msg_flags & MSG_OOB)
 		goto out;
 
 	while (1) {
 		/* If there are pending notifications, do those - and nothing else */
diff --git a/net/rose/af_rose.c b/net/rose/af_rose.c
index e98fcfbe600791..33af77246bfeb9 100644
--- a/net/rose/af_rose.c
+++ b/net/rose/af_rose.c
@@ -1214,11 +1214,10 @@ static int rose_sendmsg(struct kiocb *iocb, struct socket *sock,
 static int rose_recvmsg(struct kiocb *iocb, struct socket *sock,
 			struct msghdr *msg, size_t size, int flags)
 {
 	struct sock *sk = sock->sk;
 	struct rose_sock *rose = rose_sk(sk);
-	struct sockaddr_rose *srose = (struct sockaddr_rose *)msg->msg_name;
 	size_t copied;
 	unsigned char *asmptr;
 	struct sk_buff *skb;
 	int n, er, qbit;
 
@@ -1250,12 +1249,15 @@ static int rose_recvmsg(struct kiocb *iocb, struct socket *sock,
 		msg->msg_flags |= MSG_TRUNC;
 	}
 
 	skb_copy_datagram_iovec(skb, 0, msg->msg_iov, copied);
 
-	if (srose != NULL) {
-		memset(srose, 0, msg->msg_namelen);
+	if (msg->msg_name) {
+		struct sockaddr_rose *srose;
+
+		memset(msg->msg_name, 0, sizeof(struct full_sockaddr_rose));
+		srose = msg->msg_name;
 		srose->srose_family = AF_ROSE;
 		srose->srose_addr   = rose->dest_addr;
 		srose->srose_call   = rose->dest_call;
 		srose->srose_ndigis = rose->dest_ndigis;
 		if (msg->msg_namelen >= sizeof(struct full_sockaddr_rose)) {
diff --git a/net/rxrpc/ar-recvmsg.c b/net/rxrpc/ar-recvmsg.c
index 4b48687c3890fc..898492a8d61be8 100644
--- a/net/rxrpc/ar-recvmsg.c
+++ b/net/rxrpc/ar-recvmsg.c
@@ -141,14 +141,17 @@ int rxrpc_recvmsg(struct kiocb *iocb, struct socket *sock,
 
 		rxrpc_get_call(call);
 
 		/* copy the peer address and timestamp */
 		if (!continue_call) {
-			if (msg->msg_name && msg->msg_namelen > 0)
+			if (msg->msg_name) {
+				size_t len =
+					sizeof(call->conn->trans->peer->srx);
 				memcpy(msg->msg_name,
-				       &call->conn->trans->peer->srx,
-				       sizeof(call->conn->trans->peer->srx));
+				       &call->conn->trans->peer->srx, len);
+				msg->msg_namelen = len;
+			}
 			sock_recv_ts_and_drops(msg, &rx->sk, skb);
 		}
 
 		/* receive the message */
 		if (skb->mark != RXRPC_SKB_MARK_DATA)
diff --git a/net/socket.c b/net/socket.c
index c226aceee65b8b..fc285564e49ec1 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1838,12 +1838,14 @@ SYSCALL_DEFINE6(recvfrom, int, fd, void __user *, ubuf, size_t, size,
 	msg.msg_controllen = 0;
 	msg.msg_iovlen = 1;
 	msg.msg_iov = &iov;
 	iov.iov_len = size;
 	iov.iov_base = ubuf;
-	msg.msg_name = (struct sockaddr *)&address;
-	msg.msg_namelen = sizeof(address);
+	/* Save some cycles and don't copy the address if not needed */
+	msg.msg_name = addr ? (struct sockaddr *)&address : NULL;
+	/* We assume all kernel code knows the size of sockaddr_storage */
+	msg.msg_namelen = 0;
 	if (sock->file->f_flags & O_NONBLOCK)
 		flags |= MSG_DONTWAIT;
 	err = sock_recvmsg(sock, &msg, size, flags);
 
 	if (err >= 0 && addr != NULL) {
@@ -2219,28 +2221,29 @@ static int ___sys_recvmsg(struct socket *sock, struct msghdr __user *msg,
 			      GFP_KERNEL);
 		if (!iov)
 			goto out;
 	}
 
-	/*
-	 *      Save the user-mode address (verify_iovec will change the
-	 *      kernel msghdr to use the kernel address space)
+	/* Save the user-mode address (verify_iovec will change the
+	 * kernel msghdr to use the kernel address space)
 	 */
-
 	uaddr = (__force void __user *)msg_sys->msg_name;
 	uaddr_len = COMPAT_NAMELEN(msg);
-	if (MSG_CMSG_COMPAT & flags) {
+	if (MSG_CMSG_COMPAT & flags)
 		err = verify_compat_iovec(msg_sys, iov, &addr, VERIFY_WRITE);
-	} else
+	else
 		err = verify_iovec(msg_sys, iov, &addr, VERIFY_WRITE);
 	if (err < 0)
 		goto out_freeiov;
 	total_len = err;
 
 	cmsg_ptr = (unsigned long)msg_sys->msg_control;
 	msg_sys->msg_flags = flags & (MSG_CMSG_CLOEXEC|MSG_CMSG_COMPAT);
 
+	/* We assume all kernel code knows the size of sockaddr_storage */
+	msg_sys->msg_namelen = 0;
+
 	if (sock->file->f_flags & O_NONBLOCK)
 		flags |= MSG_DONTWAIT;
 	err = (nosec ? sock_recvmsg_nosec : sock_recvmsg)(sock, msg_sys,
 							  total_len, flags);
 	if (err < 0)
diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index 3906527259d19f..3b61851bb9276e 100644
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -978,13 +978,10 @@ static int recv_msg(struct kiocb *iocb, struct socket *sock,
 	if (unlikely(sock->state == SS_UNCONNECTED)) {
 		res = -ENOTCONN;
 		goto exit;
 	}
 
-	/* will be updated in set_orig_addr() if needed */
-	m->msg_namelen = 0;
-
 	timeout = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
 restart:
 
 	/* Look for a message in receive queue; wait if necessary */
 	while (skb_queue_empty(&sk->sk_receive_queue)) {
@@ -1089,13 +1086,10 @@ static int recv_stream(struct kiocb *iocb, struct socket *sock,
 	if (unlikely((sock->state == SS_UNCONNECTED))) {
 		res = -ENOTCONN;
 		goto exit;
 	}
 
-	/* will be updated in set_orig_addr() if needed */
-	m->msg_namelen = 0;
-
 	target = sock_rcvlowat(sk, flags & MSG_WAITALL, buf_len);
 	timeout = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
 
 restart:
 	/* Look for a message in receive queue; wait if necessary */
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index c1f403bed683ee..01625ccc3ae64a 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1752,11 +1752,10 @@ static int unix_seqpacket_recvmsg(struct kiocb *iocb, struct socket *sock,
 
 static void unix_copy_addr(struct msghdr *msg, struct sock *sk)
 {
 	struct unix_sock *u = unix_sk(sk);
 
-	msg->msg_namelen = 0;
 	if (u->addr) {
 		msg->msg_namelen = u->addr->len;
 		memcpy(msg->msg_name, u->addr->name, u->addr->len);
 	}
 }
@@ -1776,12 +1775,10 @@ static int unix_dgram_recvmsg(struct kiocb *iocb, struct socket *sock,
 
 	err = -EOPNOTSUPP;
 	if (flags&MSG_OOB)
 		goto out;
 
-	msg->msg_namelen = 0;
-
 	err = mutex_lock_interruptible(&u->readlock);
 	if (err) {
 		err = sock_intr_errno(sock_rcvtimeo(sk, noblock));
 		goto out;
 	}
@@ -1922,12 +1919,10 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
 		goto out;
 
 	target = sock_rcvlowat(sk, flags&MSG_WAITALL, size);
 	timeo = sock_rcvtimeo(sk, flags&MSG_DONTWAIT);
 
-	msg->msg_namelen = 0;
-
 	/* Lock the socket to prevent queue disordering
 	 * while sleeps in memcpy_tomsg
 	 */
 
 	if (!siocb->scm) {
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 545c08b8a1d482..5adfd94c5b85d3 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1660,12 +1660,10 @@ vsock_stream_recvmsg(struct kiocb *kiocb,
 
 	sk = sock->sk;
 	vsk = vsock_sk(sk);
 	err = 0;
 
-	msg->msg_namelen = 0;
-
 	lock_sock(sk);
 
 	if (sk->sk_state != SS_CONNECTED) {
 		/* Recvmsg is supposed to return 0 if a peer performs an
 		 * orderly shutdown. Differentiate between that case and when a
diff --git a/net/vmw_vsock/vmci_transport.c b/net/vmw_vsock/vmci_transport.c
index 9d6986634e0bfa..687360da62d9f5 100644
--- a/net/vmw_vsock/vmci_transport.c
+++ b/net/vmw_vsock/vmci_transport.c
@@ -1744,12 +1744,10 @@ static int vmci_transport_dgram_dequeue(struct kiocb *kiocb,
 	noblock = flags & MSG_DONTWAIT;
 
 	if (flags & MSG_OOB || flags & MSG_ERRQUEUE)
 		return -EOPNOTSUPP;
 
-	msg->msg_namelen = 0;
-
 	/* Retrieve the head sk_buff from the socket's receive queue. */
 	err = 0;
 	skb = skb_recv_datagram(&vsk->sk, flags, noblock, &err);
 	if (err)
 		return err;
diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
index 45a3ab5612c13c..7622789d37501f 100644
--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -1338,14 +1338,13 @@ static int x25_recvmsg(struct kiocb *iocb, struct socket *sock,
 		goto out_free_dgram;
 
 	if (sx25) {
 		sx25->sx25_family = AF_X25;
 		sx25->sx25_addr   = x25->dest_addr;
+		msg->msg_namelen = sizeof(*sx25);
 	}
 
-	msg->msg_namelen = sizeof(struct sockaddr_x25);
-
 	x25_check_rbuf(sk);
 	rc = copied;
 out_free_dgram:
 	skb_free_datagram(sk, skb);
 out:

Vulnerable code: 	msg->msg_namelen = 0;

	msg->msg_namelen = 0;
	struct sockaddr_mISDN	*maddr;
	if (msg->msg_namelen >= sizeof(struct sockaddr_mISDN)) {
		msg->msg_namelen = sizeof(struct sockaddr_mISDN);
		maddr = (struct sockaddr_mISDN *)msg->msg_name;
	} else {
		if (msg->msg_namelen)
			printk(KERN_WARNING "%s: too small namelen %d\n",
			       __func__, msg->msg_namelen);
		msg->msg_namelen = 0;
	m->msg_namelen = 0;

	struct sockaddr_at *sat = (struct sockaddr_at *)msg->msg_name;
	if (!err) {
		if (sat) {
			sat->sat_family      = AF_APPLETALK;
			sat->sat_port        = ddp->deh_sport;
			sat->sat_addr.s_node = ddp->deh_snode;
			sat->sat_addr.s_net  = ddp->deh_snet;
		}
		msg->msg_namelen = sizeof(*sat);
	msg->msg_namelen = 0;

	if (msg->msg_namelen != 0) {
		struct sockaddr_ax25 *sax = (struct sockaddr_ax25 *)msg->msg_name;
		if (sk->sk_shutdown & RCV_SHUTDOWN) {
			msg->msg_namelen = 0;
		}
		else
			msg->msg_namelen = 0;
	msg->msg_namelen = 0;

	msg->msg_namelen = 0;

		msg->msg_namelen = 0;
		msg->msg_namelen = 0;
	m->msg_namelen = 0;

	msg->msg_namelen = 0;

		kern_msg->msg_name = kern_address;
		m->msg_name = address;
	msg->msg_namelen = sizeof(*sipx);

	msg->msg_namelen = 0;

	msg->msg_namelen = 0;

	msg->msg_namelen = 0;

	msg->msg_namelen = 0;
	msg->msg_namelen = 0;

	msg->msg_namelen = 0;

	msg->msg_namelen = 0;

	msg->msg_namelen = sizeof(*sax);

	msg->msg_namelen = 0;

	msg->msg_namelen = 0;

	struct sockaddr_ll *sll;
	/*
	 *	If the address length field is there to be filled in, we fill
	 *	it in now.
	 */

	sll = &PACKET_SKB_CB(skb)->sa.ll;
	if (sock->type == SOCK_PACKET)
		msg->msg_namelen = sizeof(struct sockaddr_pkt);
	else
		msg->msg_namelen = sll->sll_halen + offsetof(struct sockaddr_ll, sll_addr);

	/*
	 *	You lose any data beyond the buffer you gave. If it worries a
	 *	user program they can ask the device for its MTU anyway.

	if (msg->msg_name)
	msg->msg_namelen = 0;

	struct sockaddr_rose *srose = (struct sockaddr_rose *)msg->msg_name;
	if (srose != NULL) {
		memset(srose, 0, msg->msg_namelen);
			if (msg->msg_name && msg->msg_namelen > 0)
				       &call->conn->trans->peer->srx,
				       sizeof(call->conn->trans->peer->srx));
	msg.msg_name = (struct sockaddr *)&address;
	msg.msg_namelen = sizeof(address);
	/*
	 *      Save the user-mode address (verify_iovec will change the
	 *      kernel msghdr to use the kernel address space)

	if (MSG_CMSG_COMPAT & flags) {
	} else
	/* will be updated in set_orig_addr() if needed */
	m->msg_namelen = 0;

	/* will be updated in set_orig_addr() if needed */
	m->msg_namelen = 0;

	msg->msg_namelen = 0;
	msg->msg_namelen = 0;

	msg->msg_namelen = 0;

	msg->msg_namelen = 0;

	msg->msg_namelen = 0;

	msg->msg_namelen = sizeof(struct sockaddr_x25);

Fixed code: 	if (msg->msg_name) {
		struct sockaddr_mISDN *maddr = msg->msg_name;

		msg->msg_namelen = sizeof(*maddr);
	/* Notes for implementing recvmsg:
	 * ===============================
	 * msg->msg_namelen should get updated by the recvmsg handlers
	 * iff msg_name != NULL. It is by default 0 to prevent
	 * returning uninitialized memory to user space.  The recvfrom
	 * handlers can assume that msg.msg_name is either NULL or has
	 * a minimum size of sizeof(struct sockaddr_storage).
	 */
	if (!err && msg->msg_name) {
		struct sockaddr_at *sat = msg->msg_name;
		sat->sat_family      = AF_APPLETALK;
		sat->sat_port        = ddp->deh_sport;
		sat->sat_addr.s_node = ddp->deh_snode;
		sat->sat_addr.s_net  = ddp->deh_snet;
		msg->msg_namelen     = sizeof(*sat);
	if (msg->msg_name) {
		struct sockaddr_ax25 *sax = msg->msg_name;
		if (sk->sk_shutdown & RCV_SHUTDOWN)

		if (kern_msg->msg_name)
			kern_msg->msg_name = kern_address;
		if (m->msg_name)
			m->msg_name = address;
		msg->msg_namelen	= sizeof(*sipx);
		msg->msg_namelen = sizeof(*sax);
	/* You lose any data beyond the buffer you gave. If it worries
	 * a user program they can ask the device for its MTU
	 * anyway.
	if (msg->msg_name) {
		/* If the address length field is there to be filled
		 * in, we fill it in now.
		 */
		if (sock->type == SOCK_PACKET) {
			msg->msg_namelen = sizeof(struct sockaddr_pkt);
		} else {
			struct sockaddr_ll *sll = &PACKET_SKB_CB(skb)->sa.ll;
			msg->msg_namelen = sll->sll_halen +
				offsetof(struct sockaddr_ll, sll_addr);
		}
	}
	if (msg->msg_name) {
		struct sockaddr_rose *srose;

		memset(msg->msg_name, 0, sizeof(struct full_sockaddr_rose));
		srose = msg->msg_name;
			if (msg->msg_name) {
				size_t len =
					sizeof(call->conn->trans->peer->srx);
				       &call->conn->trans->peer->srx, len);
				msg->msg_namelen = len;
			}
	/* Save some cycles and don't copy the address if not needed */
	msg.msg_name = addr ? (struct sockaddr *)&address : NULL;
	/* We assume all kernel code knows the size of sockaddr_storage */
	msg.msg_namelen = 0;
	/* Save the user-mode address (verify_iovec will change the
	 * kernel msghdr to use the kernel address space)
	if (MSG_CMSG_COMPAT & flags)
	else
	/* We assume all kernel code knows the size of sockaddr_storage */
	msg_sys->msg_namelen = 0;

		msg->msg_namelen = sizeof(*sx25);