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)