net: Use netlink_ns_capable to verify the permisions of netlink messages

It is possible by passing a netlink socket to a more privileged
executable and then to fool that executable into writing to the socket
data that happens to be valid netlink message to do something that
privileged executable did not intend to do.

To keep this from happening replace bare capable and ns_capable calls
with netlink_capable, netlink_net_calls and netlink_ns_capable calls.
Which act the same as the previous calls except they verify that the
opener of the socket had the desired permissions as well.

Reported-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 2 deletions

diff --git a/net/can/gw.c b/net/can/gw.c
index ac31891967da..050a2110d43f 100644
--- a/net/can/gw.c
+++ b/net/can/gw.c
@@ -804,7 +804,7 @@ static int cgw_create_job(struct sk_buff *skb,  struct nlmsghdr *nlh)
         u8 limhops = 0;
         int err = 0;
 
-        if (!capable(CAP_NET_ADMIN))
+        if (!netlink_capable(skb, CAP_NET_ADMIN))
                 return -EPERM;
 
         if (nlmsg_len(nlh) < sizeof(*r))
@@ -893,7 +893,7 @@ static int cgw_remove_job(struct sk_buff *skb, struct nlmsghdr *nlh)
         u8 limhops = 0;
         int err = 0;
 
-        if (!capable(CAP_NET_ADMIN))
+        if (!netlink_capable(skb, CAP_NET_ADMIN))
                 return -EPERM;
 
         if (nlmsg_len(nlh) < sizeof(*r))