1 files changed, 35 insertions, 1 deletions

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index d46da6cb92e4..da3163d15ef0 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1361,7 +1361,7 @@ 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, *frag __maybe_unused = NULL;
 	int err;
 
 	if (flags&MSG_OOB)
@@ -1373,6 +1373,35 @@ static int netlink_recvmsg(struct kiocb *kiocb, struct socket *sock,
 	if (skb == NULL)
 		goto out;
 
+#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.
+		 *
+		 * 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 (need_compat) {
+			struct sk_buff *compskb = skb_shinfo(skb)->frag_list;
+			skb_get(compskb);
+			kfree_skb(skb);
+			skb = compskb;
+		} else {
+			frag = skb_shinfo(skb)->frag_list;
+			skb_shinfo(skb)->frag_list = NULL;
+		}
+	}
+#endif
+
 	msg->msg_namelen = 0;
 
 	copied = skb->len;
@@ -1403,6 +1432,11 @@ static int netlink_recvmsg(struct kiocb *kiocb, struct socket *sock,
 	siocb->scm->creds = *NETLINK_CREDS(skb);
 	if (flags & MSG_TRUNC)
 		copied = skb->len;
+
+#ifdef CONFIG_COMPAT_NETLINK_MESSAGES
+	skb_shinfo(skb)->frag_list = frag;
+#endif
+
 	skb_free_datagram(sk, skb);
 
 	if (nlk->cb && atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf / 2)