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

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

From: Richard Alpe <redacted>

[ Upstream commit 45e093ae2830cd1264677d47ff9a95a71f5d9f9c ]

Make sure the socket for which the user is listing publication exists
before parsing the socket netlink attributes.

Prior to this patch a call without any socket caused a NULL pointer
dereference in tipc_nl_publ_dump().

Tested-and-reported-by: Baozeng Ding [off-list ref]
Signed-off-by: Richard Alpe <redacted>
Acked-by: Jon Maloy <redacted>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/tipc/socket.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c

@@ -2807,6 +2807,9 @@ int tipc_nl_publ_dump(struct sk_buff *sk
 		if (err)
 			return err;
 
+		if (!attrs[TIPC_NLA_SOCK])
+			return -EINVAL;
+
 		err = nla_parse_nested(sock, TIPC_NLA_SOCK_MAX,
 				       attrs[TIPC_NLA_SOCK],
 				       tipc_nl_sock_policy);