inet: prevent leakage of uninitialized memory to user in recv syscalls

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@gmail.com>
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>

8 files changed, 17 insertions, 38 deletions

diff --git a/net/ieee802154/dgram.c b/net/ieee802154/dgram.c
index 581a59504bd5..1865fdf5a5a5 100644
--- a/net/ieee802154/dgram.c
+++ b/net/ieee802154/dgram.c
@@ -315,9 +315,8 @@ static int dgram_recvmsg(struct kiocb *iocb, struct sock *sk,
         if (saddr) {
                 saddr->family = AF_IEEE802154;
                 saddr->addr = mac_cb(skb)->sa;
-        }
-        if (addr_len)
                 *addr_len = sizeof(*saddr);
+        }
 
         if (flags & MSG_TRUNC)
                 copied = skb->len;
diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
index 9afbdb19f4a2..aacefa0caa36 100644
--- a/net/ipv4/ping.c
+++ b/net/ipv4/ping.c
@@ -830,8 +830,6 @@ int ping_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 {
         struct inet_sock *isk = inet_sk(sk);
         int family = sk->sk_family;
-        struct sockaddr_in *sin;
-        struct sockaddr_in6 *sin6;
         struct sk_buff *skb;
         int copied, err;
 
@@ -841,13 +839,6 @@ int ping_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
         if (flags & MSG_OOB)
                 goto out;
 
-        if (addr_len) {
-                if (family == AF_INET)
-                        *addr_len = sizeof(*sin);
-                else if (family == AF_INET6 && addr_len)
-                        *addr_len = sizeof(*sin6);
-        }
-
         if (flags & MSG_ERRQUEUE) {
                 if (family == AF_INET) {
                         return ip_recv_error(sk, msg, len);
@@ -877,11 +868,13 @@ int ping_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 
         /* Copy the address and add cmsg data. */
         if (family == AF_INET) {
-                sin = (struct sockaddr_in *) 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);
@@ -890,17 +883,19 @@ int ping_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
         } else if (family == AF_INET6) {
                 struct ipv6_pinfo *np = inet6_sk(sk);
                 struct ipv6hdr *ip6 = ipv6_hdr(skb);
-                sin6 = (struct sockaddr_in6 *) msg->msg_name;
+                struct sockaddr_in6 *sin6 =
+                        (struct sockaddr_in6 *)msg->msg_name;
+
                 sin6->sin6_family = AF_INET6;
                 sin6->sin6_port = 0;
                 sin6->sin6_addr = ip6->saddr;
-
                 sin6->sin6_flowinfo = 0;
                 if (np->sndflow)
                         sin6->sin6_flowinfo = ip6_flowinfo(ip6);
 
                 sin6->sin6_scope_id = ipv6_iface_scope_id(&sin6->sin6_addr,
                                                           IP6CB(skb)->iif);
+                *addr_len = sizeof(*sin6);
 
                 if (inet6_sk(sk)->rxopt.all)
                         pingv6_ops.ip6_datagram_recv_ctl(sk, msg, skb);
diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
index 41e1d2845c8f..5cb8ddb505ee 100644
--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c
@@ -696,9 +696,6 @@ 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;
@@ -726,6 +723,7 @@ 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 89909dd730dd..998431cd471a 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1235,12 +1235,6 @@ 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);
 
@@ -1302,6 +1296,7 @@ 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 3c00842b0079..e24ff1df0401 100644
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -465,9 +465,6 @@ 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);
 
@@ -506,6 +503,7 @@ static int rawv6_recvmsg(struct kiocb *iocb, struct sock *sk,
                 sin6->sin6_flowinfo = 0;
                 sin6->sin6_scope_id = ipv6_iface_scope_id(&sin6->sin6_addr,
                                                           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 f3893e897f72..81eb8cf8389b 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -392,9 +392,6 @@ 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);
 
@@ -480,7 +477,7 @@ try_again:
                                 ipv6_iface_scope_id(&sin6->sin6_addr,
                                                     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 571db8dd2292..da1a1cee1a08 100644
--- a/net/l2tp/l2tp_ip.c
+++ b/net/l2tp/l2tp_ip.c
@@ -518,9 +518,6 @@ 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;
@@ -543,6 +540,7 @@ 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 12c30f3e643e..38946b26e471 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);