[PATCH 3.2 185/221] ip: zero sockaddr returned on error queue

[Ben Hutchings]

3.2.69-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Willem de Bruijn <willemb@xxxxxxxxxx>

[ Upstream commit f812116b174e59a350acc8e4856213a166a91222 ]

The sockaddr is returned in IP(V6)_RECVERR as part of errhdr. That
structure is defined and allocated on the stack as

    struct {
            struct sock_extended_err ee;
            struct sockaddr_in(6)    offender;
    } errhdr;

The second part is only initialized for certain SO_EE_ORIGIN values.
Always initialize it completely.

An MTU exceeded error on a SOCK_RAW/IPPROTO_RAW is one example that
would return uninitialized bytes.

Signed-off-by: Willem de Bruijn <willemb@xxxxxxxxxx>

----

Also verified that there is no padding between errhdr.ee and
errhdr.offender that could leak additional kernel data.
Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 net/ipv4/ip_sockglue.c |  8 ++------
 net/ipv6/datagram.c    | 10 +++-------
 2 files changed, 5 insertions(+), 13 deletions(-)

--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -416,15 +416,11 @@ int ip_recv_error(struct sock *sk, struc
 
 	memcpy(&errhdr.ee, &serr->ee, sizeof(struct sock_extended_err));
 	sin = &errhdr.offender;
-	sin->sin_family = AF_UNSPEC;
+	memset(sin, 0, sizeof(*sin));
 	if (serr->ee.ee_origin == SO_EE_ORIGIN_ICMP) {
-		struct inet_sock *inet = inet_sk(sk);
-
 		sin->sin_family = AF_INET;
 		sin->sin_addr.s_addr = ip_hdr(skb)->saddr;
-		sin->sin_port = 0;
-		memset(&sin->sin_zero, 0, sizeof(sin->sin_zero));
-		if (inet->cmsg_flags)
+		if (inet_sk(sk)->cmsg_flags)
 			ip_cmsg_recv(msg, skb);
 	}
 
--- a/net/ipv6/datagram.c
+++ b/net/ipv6/datagram.c
@@ -371,12 +371,10 @@ int ipv6_recv_error(struct sock *sk, str
 
 	memcpy(&errhdr.ee, &serr->ee, sizeof(struct sock_extended_err));
 	sin = &errhdr.offender;
-	sin->sin6_family = AF_UNSPEC;
+	memset(sin, 0, sizeof(*sin));
+
 	if (serr->ee.ee_origin != SO_EE_ORIGIN_LOCAL) {
 		sin->sin6_family = AF_INET6;
-		sin->sin6_flowinfo = 0;
-		sin->sin6_port = 0;
-		sin->sin6_scope_id = 0;
 		if (skb->protocol == htons(ETH_P_IPV6)) {
 			ipv6_addr_copy(&sin->sin6_addr, &ipv6_hdr(skb)->saddr);
 			if (np->rxopt.all)
@@ -384,11 +382,9 @@ int ipv6_recv_error(struct sock *sk, str
 			if (ipv6_addr_type(&sin->sin6_addr) & IPV6_ADDR_LINKLOCAL)
 				sin->sin6_scope_id = IP6CB(skb)->iif;
 		} else {
-			struct inet_sock *inet = inet_sk(sk);
-
 			ipv6_addr_set_v4mapped(ip_hdr(skb)->saddr,
 					       &sin->sin6_addr);
-			if (inet->cmsg_flags)
+			if (inet_sk(sk)->cmsg_flags)
 				ip_cmsg_recv(msg, skb);
 		}
 	}

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