[NETLINK]: Fix use after free in netlink_recvmsg

When the user passes in MSG_TRUNC the skb is used after getting freed.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 4 deletions

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 7fc6b4da4f02..ac1ceadf4ed3 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1246,16 +1246,14 @@ static int netlink_recvmsg(struct kiocb *kiocb, struct socket *sock,
                 siocb->scm = &scm;
         }
         siocb->scm->creds = *NETLINK_CREDS(skb);
+        if (flags & MSG_TRUNC)
+                copied = skb->len;
         skb_free_datagram(sk, skb);
 
         if (nlk->cb && atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf / 2)
                 netlink_dump(sk);
 
         scm_recv(sock, msg, siocb->scm, flags);
-
-        if (flags & MSG_TRUNC)
-                copied = skb->len;
-
 out:
         netlink_rcv_wake(sk);
         return err ? : copied;