[PATCH 3.8 17/91] inet: prevent leakage of uninitialized memory to user in recv syscalls

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3.8.13.15 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Hannes Frederic Sowa <hannes@xxxxxxxxxxxxxxxxxxx>

[ Upstream commit bceaa90240b6019ed73b49965eac7d167610be69 ]

Only update *addr_len when we actually fill in sockaddr, otherwise we
can return uninitialized memory from the stack to the caller in the
recvfrom, recvmmsg and recvmsg syscalls. Drop the the (addr_len == NULL)
checks because we only get called with a valid addr_len pointer either
from sock_common_recvmsg or inet_recvmsg.

If a blocking read waits on a socket which is concurrently shut down we
now return zero and set msg_msgnamelen to 0.

Reported-by: mpb <mpb.mail@xxxxxxxxx>
Suggested-by: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Signed-off-by: Hannes Frederic Sowa <hannes@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[ kamal: backport to 3.8 (context) ]
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
 net/ipv4/ping.c       | 9 ++++-----
 net/ipv4/raw.c        | 4 +---
 net/ipv4/udp.c        | 7 +------
 net/ipv6/raw.c        | 4 +---
 net/ipv6/udp.c        | 5 +----
 net/l2tp/l2tp_ip.c    | 4 +---
 net/phonet/datagram.c | 9 ++++-----
 7 files changed, 13 insertions(+), 29 deletions(-)

diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
index dc454cc..a690121 100644
--- a/net/ipv4/ping.c
+++ b/net/ipv4/ping.c
@@ -627,7 +627,6 @@ static int ping_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 			size_t len, int noblock, int flags, int *addr_len)
 {
 	struct inet_sock *isk = inet_sk(sk);
-	struct sockaddr_in *sin = (struct sockaddr_in *)msg->msg_name;
 	struct sk_buff *skb;
 	int copied, err;
 
@@ -637,9 +636,6 @@ static int ping_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 	if (flags & MSG_OOB)
 		goto out;
 
-	if (addr_len)
-		*addr_len = sizeof(*sin);
-
 	if (flags & MSG_ERRQUEUE)
 		return ip_recv_error(sk, msg, len);
 
@@ -661,11 +657,14 @@ static int ping_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 	sock_recv_timestamp(msg, sk, skb);
 
 	/* Copy the address. */
-	if (sin) {
+	if (msg->msg_name) {
+		struct sockaddr_in *sin = (struct sockaddr_in *)msg->msg_name;
+
 		sin->sin_family = AF_INET;
 		sin->sin_port = 0 /* skb->h.uh->source */;
 		sin->sin_addr.s_addr = ip_hdr(skb)->saddr;
 		memset(sin->sin_zero, 0, sizeof(sin->sin_zero));
+		*addr_len = sizeof(*sin);
 	}
 	if (isk->cmsg_flags)
 		ip_cmsg_recv(msg, skb);
diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
index a9b4ef3..5f42d6d 100644
--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c
@@ -694,9 +694,6 @@ static int raw_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 	if (flags & MSG_OOB)
 		goto out;
 
-	if (addr_len)
-		*addr_len = sizeof(*sin);
-
 	if (flags & MSG_ERRQUEUE) {
 		err = ip_recv_error(sk, msg, len);
 		goto out;
@@ -724,6 +721,7 @@ static int raw_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 		sin->sin_addr.s_addr = ip_hdr(skb)->saddr;
 		sin->sin_port = 0;
 		memset(&sin->sin_zero, 0, sizeof(sin->sin_zero));
+		*addr_len = sizeof(*sin);
 	}
 	if (inet->cmsg_flags)
 		ip_cmsg_recv(msg, skb);
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 21e1eec..83e3273 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1180,12 +1180,6 @@ int udp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 	int is_udplite = IS_UDPLITE(sk);
 	bool slow;
 
-	/*
-	 *	Check any passed addresses
-	 */
-	if (addr_len)
-		*addr_len = sizeof(*sin);
-
 	if (flags & MSG_ERRQUEUE)
 		return ip_recv_error(sk, msg, len);
 
@@ -1247,6 +1241,7 @@ try_again:
 		sin->sin_port = udp_hdr(skb)->source;
 		sin->sin_addr.s_addr = ip_hdr(skb)->saddr;
 		memset(sin->sin_zero, 0, sizeof(sin->sin_zero));
+		*addr_len = sizeof(*sin);
 	}
 	if (inet->cmsg_flags)
 		ip_cmsg_recv(msg, skb);
diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
index 70fa814..276faf6 100644
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -460,9 +460,6 @@ static int rawv6_recvmsg(struct kiocb *iocb, struct sock *sk,
 	if (flags & MSG_OOB)
 		return -EOPNOTSUPP;
 
-	if (addr_len)
-		*addr_len=sizeof(*sin6);
-
 	if (flags & MSG_ERRQUEUE)
 		return ipv6_recv_error(sk, msg, len);
 
@@ -502,6 +499,7 @@ static int rawv6_recvmsg(struct kiocb *iocb, struct sock *sk,
 		sin6->sin6_scope_id = 0;
 		if (ipv6_addr_type(&sin6->sin6_addr) & IPV6_ADDR_LINKLOCAL)
 			sin6->sin6_scope_id = IP6CB(skb)->iif;
+		*addr_len = sizeof(*sin6);
 	}
 
 	sock_recv_ts_and_drops(msg, sk, skb);
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 4ca80fc..f8236a3 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -349,9 +349,6 @@ int udpv6_recvmsg(struct kiocb *iocb, struct sock *sk,
 	int is_udp4;
 	bool slow;
 
-	if (addr_len)
-		*addr_len = sizeof(struct sockaddr_in6);
-
 	if (flags & MSG_ERRQUEUE)
 		return ipv6_recv_error(sk, msg, len);
 
@@ -436,7 +433,7 @@ try_again:
 			if (ipv6_addr_type(&sin6->sin6_addr) & IPV6_ADDR_LINKLOCAL)
 				sin6->sin6_scope_id = IP6CB(skb)->iif;
 		}
-
+		*addr_len = sizeof(*sin6);
 	}
 	if (is_udp4) {
 		if (inet->cmsg_flags)
diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c
index 61d8b75..2bc35bc 100644
--- a/net/l2tp/l2tp_ip.c
+++ b/net/l2tp/l2tp_ip.c
@@ -510,9 +510,6 @@ static int l2tp_ip_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *m
 	if (flags & MSG_OOB)
 		goto out;
 
-	if (addr_len)
-		*addr_len = sizeof(*sin);
-
 	skb = skb_recv_datagram(sk, flags, noblock, &err);
 	if (!skb)
 		goto out;
@@ -535,6 +532,7 @@ static int l2tp_ip_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *m
 		sin->sin_addr.s_addr = ip_hdr(skb)->saddr;
 		sin->sin_port = 0;
 		memset(&sin->sin_zero, 0, sizeof(sin->sin_zero));
+		*addr_len = sizeof(*sin);
 	}
 	if (inet->cmsg_flags)
 		ip_cmsg_recv(msg, skb);
diff --git a/net/phonet/datagram.c b/net/phonet/datagram.c
index 12c30f3..38946b2 100644
--- a/net/phonet/datagram.c
+++ b/net/phonet/datagram.c
@@ -139,9 +139,6 @@ static int pn_recvmsg(struct kiocb *iocb, struct sock *sk,
 			MSG_CMSG_COMPAT))
 		goto out_nofree;
 
-	if (addr_len)
-		*addr_len = sizeof(sa);
-
 	skb = skb_recv_datagram(sk, flags, noblock, &rval);
 	if (skb == NULL)
 		goto out_nofree;
@@ -162,8 +159,10 @@ static int pn_recvmsg(struct kiocb *iocb, struct sock *sk,
 
 	rval = (flags & MSG_TRUNC) ? skb->len : copylen;
 
-	if (msg->msg_name != NULL)
-		memcpy(msg->msg_name, &sa, sizeof(struct sockaddr_pn));
+	if (msg->msg_name != NULL) {
+		memcpy(msg->msg_name, &sa, sizeof(sa));
+		*addr_len = sizeof(sa);
+	}
 
 out:
 	skb_free_datagram(sk, skb);
-- 
1.8.3.2

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