1 files changed, 16 insertions, 40 deletions

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 2cbf380377d5..980fe4ad0016 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1406,7 +1406,7 @@ static int netlink_recvmsg(struct kiocb *kiocb, struct socket *sock,
         struct netlink_sock *nlk = nlk_sk(sk);
         int noblock = flags&MSG_DONTWAIT;
         size_t copied;
-        struct sk_buff *skb;
+        struct sk_buff *skb, *data_skb;
         int err;
 
         if (flags&MSG_OOB)
@@ -1418,59 +1418,35 @@ static int netlink_recvmsg(struct kiocb *kiocb, struct socket *sock,
         if (skb == NULL)
                 goto out;
 
+        data_skb = skb;
+
 #ifdef CONFIG_COMPAT_NETLINK_MESSAGES
         if (unlikely(skb_shinfo(skb)->frag_list)) {
-                bool need_compat = !!(flags & MSG_CMSG_COMPAT);
-
                 /*
-                 * If this skb has a frag_list, then here that means that
-                 * we will have to use the frag_list skb for compat tasks
-                 * and the regular skb for non-compat tasks.
+                 * If this skb has a frag_list, then here that means that we
+                 * will have to use the frag_list skb's data for compat tasks
+                 * and the regular skb's data for normal (non-compat) tasks.
                  *
-                 * The skb might (and likely will) be cloned, so we can't
-                 * just reset frag_list and go on with things -- we need to
-                 * keep that. For the compat case that's easy -- simply get
-                 * a reference to the compat skb and free the regular one
-                 * including the frag. For the non-compat case, we need to
-                 * avoid sending the frag to the user -- so assign NULL but
-                 * restore it below before freeing the skb.
+                 * If we need to send the compat skb, assign it to the
+                 * 'data_skb' variable so that it will be used below for data
+                 * copying. We keep 'skb' for everything else, including
+                 * freeing both later.
                  */
-                if (need_compat) {
-                        struct sk_buff *compskb = skb_shinfo(skb)->frag_list;
-                        skb_get(compskb);
-                        kfree_skb(skb);
-                        skb = compskb;
-                } else {
-                        /*
-                         * Before setting frag_list to NULL, we must get a
-                         * private copy of skb if shared (because of MSG_PEEK)
-                         */
-                        if (skb_shared(skb)) {
-                                struct sk_buff *nskb;
-
-                                nskb = pskb_copy(skb, GFP_KERNEL);
-                                kfree_skb(skb);
-                                skb = nskb;
-                                err = -ENOMEM;
-                                if (!skb)
-                                        goto out;
-                        }
-                        kfree_skb(skb_shinfo(skb)->frag_list);
-                        skb_shinfo(skb)->frag_list = NULL;
-                }
+                if (flags & MSG_CMSG_COMPAT)
+                        data_skb = skb_shinfo(skb)->frag_list;
         }
 #endif
 
         msg->msg_namelen = 0;
 
-        copied = skb->len;
+        copied = data_skb->len;
         if (len < copied) {
                 msg->msg_flags |= MSG_TRUNC;
                 copied = len;
         }
 
-        skb_reset_transport_header(skb);
-        err = skb_copy_datagram_iovec(skb, 0, msg->msg_iov, copied);
+        skb_reset_transport_header(data_skb);
+        err = skb_copy_datagram_iovec(data_skb, 0, msg->msg_iov, copied);
 
         if (msg->msg_name) {
                 struct sockaddr_nl *addr = (struct sockaddr_nl *)msg->msg_name;
@@ -1490,7 +1466,7 @@ static int netlink_recvmsg(struct kiocb *kiocb, struct socket *sock,
         }
         siocb->scm->creds = *NETLINK_CREDS(skb);
         if (flags & MSG_TRUNC)
-                copied = skb->len;
+                copied = data_skb->len;
 
         skb_free_datagram(sk, skb);