net: rework recvmsg handler msg_name and msg_namelen logic

CVE-2013-7266

BugLink: http://bugs.launchpad.net/bugs/1267081

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>
(back ported from commit f3d3342602f8bcbf37d7c46641cb9bca7618eb1c)
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
Acked-by: Andy Whitcroft <andy.whitcroft@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>

23 files changed, 53 insertions, 83 deletions

diff --git a/net/appletalk/ddp.c b/net/appletalk/ddp.c
index b1a4290996b5..5eae3606f32f 100644
--- a/net/appletalk/ddp.c
+++ b/net/appletalk/ddp.c
@@ -1703,7 +1703,6 @@ static int atalk_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr
 			 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;
@@ -1728,14 +1727,13 @@ static int atalk_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr
 	}
 	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. */
diff --git a/net/atm/common.c b/net/atm/common.c
index 65737b81059e..0baf05e8d34b 100644
--- a/net/atm/common.c
+++ b/net/atm/common.c
@@ -473,8 +473,6 @@ int vcc_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg,
 	struct sk_buff *skb;
 	int copied, error = -EINVAL;
 
-	msg->msg_namelen = 0;
-
 	if (sock->state != SS_CONNECTED)
 		return -ENOTCONN;
 	if (flags & ~MSG_DONTWAIT)		/* only handle MSG_DONTWAIT */
diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
index 8613bd1ddabe..6b9d62b5d820 100644
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -1648,11 +1648,11 @@ static int ax25_recvmsg(struct kiocb *iocb, struct socket *sock,
 
 	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,
diff --git a/net/bluetooth/af_bluetooth.c b/net/bluetooth/af_bluetooth.c
index d7239ddd6e20..143b8a7c1c47 100644
--- a/net/bluetooth/af_bluetooth.c
+++ b/net/bluetooth/af_bluetooth.c
@@ -240,8 +240,6 @@ int bt_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 	if (flags & (MSG_OOB))
 		return -EOPNOTSUPP;
 
-	msg->msg_namelen = 0;
-
 	if (!(skb = skb_recv_datagram(sk, flags, noblock, &err))) {
 		if (sk->sk_shutdown & RCV_SHUTDOWN)
 			return 0;
diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c
index 45caaaa4ace4..0e0f517d84d8 100644
--- a/net/bluetooth/hci_sock.c
+++ b/net/bluetooth/hci_sock.c
@@ -370,8 +370,6 @@ static int hci_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 	if (!(skb = skb_recv_datagram(sk, flags, noblock, &err)))
 		return err;
 
-	msg->msg_namelen = 0;
-
 	copied = skb->len;
 	if (len < copied) {
 		msg->msg_flags |= MSG_TRUNC;
diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c
index 1db0132f4965..3fabaad011c7 100644
--- a/net/bluetooth/rfcomm/sock.c
+++ b/net/bluetooth/rfcomm/sock.c
@@ -652,15 +652,12 @@ static int rfcomm_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 
 	if (test_and_clear_bit(RFCOMM_DEFER_SETUP, &d->flags)) {
 		rfcomm_dlc_accept(d);
-		msg->msg_namelen = 0;
 		return 0;
 	}
 
 	if (flags & MSG_OOB)
 		return -EOPNOTSUPP;
 
-	msg->msg_namelen = 0;
-
 	BT_DBG("sk %p size %zu", sk, size);
 
 	lock_sock(sk);
diff --git a/net/compat.c b/net/compat.c
index da3d0fce433a..d325d16f8eaa 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -91,7 +91,8 @@ int verify_compat_iovec(struct msghdr *kern_msg, struct iovec *kern_iov,
 			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;
 
diff --git a/net/core/iovec.c b/net/core/iovec.c
index f911e665a7db..39369e90c9fc 100644
--- a/net/core/iovec.c
+++ b/net/core/iovec.c
@@ -47,7 +47,8 @@ int verify_iovec(struct msghdr *m, struct iovec *iov, struct sockaddr *address,
 			if (err < 0)
 				return err;
 		}
-		m->msg_name = address;
+		if (m->msg_name)
+			m->msg_name = address;
 	} else {
 		m->msg_name = NULL;
 	}
diff --git a/net/ipx/af_ipx.c b/net/ipx/af_ipx.c
index 66c7a20011f3..25931b3752b6 100644
--- a/net/ipx/af_ipx.c
+++ b/net/ipx/af_ipx.c
@@ -1808,8 +1808,6 @@ static int ipx_recvmsg(struct kiocb *iocb, struct socket *sock,
 	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;
@@ -1817,6 +1815,7 @@ static int ipx_recvmsg(struct kiocb *iocb, struct socket *sock,
 		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;
 
diff --git a/net/irda/af_irda.c b/net/irda/af_irda.c
index bfb325de67cf..7cb7613d2ec7 100644
--- a/net/irda/af_irda.c
+++ b/net/irda/af_irda.c
@@ -1338,8 +1338,6 @@ static int irda_recvmsg_dgram(struct kiocb *iocb, struct socket *sock,
 	if ((err = sock_error(sk)) < 0)
 		return err;
 
-	msg->msg_namelen = 0;
-
 	skb = skb_recv_datagram(sk, flags & ~MSG_DONTWAIT,
 				flags & MSG_DONTWAIT, &err);
 	if (!skb)
@@ -1402,8 +1400,6 @@ static int irda_recvmsg_stream(struct kiocb *iocb, struct socket *sock,
 	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);
diff --git a/net/iucv/af_iucv.c b/net/iucv/af_iucv.c
index f605b238bd6f..bada1b9c670b 100644
--- a/net/iucv/af_iucv.c
+++ b/net/iucv/af_iucv.c
@@ -1160,8 +1160,6 @@ static int iucv_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 	struct sk_buff *skb, *rskb, *cskb;
 	int err = 0;
 
-	msg->msg_namelen = 0;
-
 	if ((sk->sk_state == IUCV_DISCONN || sk->sk_state == IUCV_SEVERED) &&
 	    skb_queue_empty(&iucv->backlog_skb_q) &&
 	    skb_queue_empty(&sk->sk_receive_queue) &&
diff --git a/net/key/af_key.c b/net/key/af_key.c
index 3f55faae3fb0..3e5d0dceb995 100644
--- a/net/key/af_key.c
+++ b/net/key/af_key.c
@@ -3597,7 +3597,6 @@ static int pfkey_recvmsg(struct kiocb *kiocb,
 	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;
diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c
index 8a814a59fed1..606b6adac1ca 100644
--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -674,8 +674,6 @@ static int llc_ui_recvmsg(struct kiocb *iocb, struct socket *sock,
 	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))
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index fc91ff6907cb..39a6d5d7afcf 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1400,8 +1400,6 @@ static int netlink_recvmsg(struct kiocb *kiocb, struct socket *sock,
 	}
 #endif
 
-	msg->msg_namelen = 0;
-
 	copied = data_skb->len;
 	if (len < copied) {
 		msg->msg_flags |= MSG_TRUNC;
diff --git a/net/netrom/af_netrom.c b/net/netrom/af_netrom.c
index 7a834952f67f..ad1ec1b9f22f 100644
--- a/net/netrom/af_netrom.c
+++ b/net/netrom/af_netrom.c
@@ -1184,10 +1184,9 @@ static int nr_recvmsg(struct kiocb *iocb, struct socket *sock,
 		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);
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index f084e01b8089..06707d0538b0 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1423,7 +1423,6 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
 	struct sock *sk = sock->sk;
 	struct sk_buff *skb;
 	int copied, err;
-	struct sockaddr_ll *sll;
 
 	err = -EINVAL;
 	if (flags & ~(MSG_PEEK|MSG_DONTWAIT|MSG_TRUNC|MSG_CMSG_COMPAT))
@@ -1455,22 +1454,10 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
 	if (skb == NULL)
 		goto out;
 
-	/*
-	 *	If the address length field is there to be filled in, we fill
-	 *	it in now.
+	/* You lose any data beyond the buffer you gave. If it worries
+	 * a user program they can ask the device for its MTU
+	 * anyway.
 	 */
-
-	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.
-	 */
-
 	copied = skb->len;
 	if (copied > len) {
 		copied = len;
@@ -1483,9 +1470,20 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
 
 	sock_recv_timestamp(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;
diff --git a/net/rds/recv.c b/net/rds/recv.c
index c45a881cf576..a11cab901d27 100644
--- a/net/rds/recv.c
+++ b/net/rds/recv.c
@@ -410,8 +410,6 @@ int rds_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg,
 
 	rdsdebug("size %zu flags 0x%x timeo %ld\n", size, msg_flags, timeo);
 
-	msg->msg_namelen = 0;
-
 	if (msg_flags & MSG_OOB)
 		goto out;
 
diff --git a/net/rose/af_rose.c b/net/rose/af_rose.c
index 2984999dc59e..08a86f62f5bb 100644
--- a/net/rose/af_rose.c
+++ b/net/rose/af_rose.c
@@ -1238,7 +1238,6 @@ static int rose_recvmsg(struct kiocb *iocb, struct socket *sock,
 {
 	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;
@@ -1274,8 +1273,11 @@ static int rose_recvmsg(struct kiocb *iocb, struct socket *sock,
 
 	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;
diff --git a/net/rxrpc/ar-recvmsg.c b/net/rxrpc/ar-recvmsg.c
index a39bf97f8830..d5630d915d9c 100644
--- a/net/rxrpc/ar-recvmsg.c
+++ b/net/rxrpc/ar-recvmsg.c
@@ -142,10 +142,13 @@ int rxrpc_recvmsg(struct kiocb *iocb, struct socket *sock,
 
 		/* 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_timestamp(msg, &rx->sk, skb);
 		}
 
diff --git a/net/socket.c b/net/socket.c
index 9f8cd744f0b0..06e8f3d1db2f 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1744,8 +1744,10 @@ SYSCALL_DEFINE6(recvfrom, int, fd, void __user *, ubuf, size_t, size,
 	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);
@@ -2033,18 +2035,16 @@ SYSCALL_DEFINE3(recvmsg, int, fd, struct msghdr __user *, msg,
 			goto out_put;
 	}
 
-	/*
-	 *      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,
 					  (struct sockaddr *)&addr,
 					  VERIFY_WRITE);
-	} else
+	else
 		err = verify_iovec(&msg_sys, iov,
 				   (struct sockaddr *)&addr,
 				   VERIFY_WRITE);
@@ -2055,6 +2055,9 @@ SYSCALL_DEFINE3(recvmsg, int, fd, struct msghdr __user *, msg,
 	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 = sock_recvmsg(sock, &msg_sys, total_len, flags);
diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index eccb86b9c370..124f1a29e63d 100644
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -917,9 +917,6 @@ static int recv_msg(struct kiocb *iocb, struct socket *sock,
 		goto exit;
 	}
 
-	/* will be updated in set_orig_addr() if needed */
-	m->msg_namelen = 0;
-
 restart:
 
 	/* Look for a message in receive queue; wait if necessary */
@@ -1053,9 +1050,6 @@ static int recv_stream(struct kiocb *iocb, struct socket *sock,
 		goto exit;
 	}
 
-	/* will be updated in set_orig_addr() if needed */
-	m->msg_namelen = 0;
-
 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 d146b76840b5..bb0b0082ee02 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1682,7 +1682,6 @@ 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);
@@ -1705,8 +1704,6 @@ static int unix_dgram_recvmsg(struct kiocb *iocb, struct socket *sock,
 	if (flags&MSG_OOB)
 		goto out;
 
-	msg->msg_namelen = 0;
-
 	mutex_lock(&u->readlock);
 
 	skb = skb_recv_datagram(sk, flags, noblock, &err);
@@ -1832,8 +1829,6 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
 	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
 	 */
diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
index 2e9e30025d60..40c447fc20aa 100644
--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -1294,10 +1294,9 @@ static int x25_recvmsg(struct kiocb *iocb, struct socket *sock,
 	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);
-
 	lock_sock(sk);
 	x25_check_rbuf(sk);
 	release_sock(sk);