[PATCH 4.14 27/52] tun: free skb in early errors

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Wei Xu <w...@redhat.com>


[ Upstream commit c33ee15b3820a03cf8229ba9415084197b827f8c ]

tun_recvmsg() supports accepting skb by msg_control after
commit ac77cfd4258f ("tun: support receiving skb through msg_control"),
the skb if presented should be freed no matter how far it can go
along, otherwise it would be leaked.

This patch fixes several missed cases.

Signed-off-by: Wei Xu <w...@redhat.com>
Reported-by: Matthew Rosato <mjros...@linux.vnet.ibm.com>
Acked-by: Michael S. Tsirkin <m...@redhat.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 drivers/net/tun.c |   24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1734,8 +1734,11 @@ static ssize_t tun_do_read(struct tun_st
 
        tun_debug(KERN_INFO, tun, "tun_do_read\n");
 
-       if (!iov_iter_count(to))
+       if (!iov_iter_count(to)) {
+               if (skb)
+                       kfree_skb(skb);
                return 0;
+       }
 
        if (!skb) {
                /* Read frames from ring */
@@ -1851,22 +1854,24 @@ static int tun_recvmsg(struct socket *so
 {
        struct tun_file *tfile = container_of(sock, struct tun_file, socket);
        struct tun_struct *tun = __tun_get(tfile);
+       struct sk_buff *skb = m->msg_control;
        int ret;
 
-       if (!tun)
-               return -EBADFD;
+       if (!tun) {
+               ret = -EBADFD;
+               goto out_free_skb;
+       }
 
        if (flags & ~(MSG_DONTWAIT|MSG_TRUNC|MSG_ERRQUEUE)) {
                ret = -EINVAL;
-               goto out;
+               goto out_put_tun;
        }
        if (flags & MSG_ERRQUEUE) {
                ret = sock_recv_errqueue(sock->sk, m, total_len,
                                         SOL_PACKET, TUN_TX_TIMESTAMP);
                goto out;
        }
-       ret = tun_do_read(tun, tfile, &m->msg_iter, flags & MSG_DONTWAIT,
-                         m->msg_control);
+       ret = tun_do_read(tun, tfile, &m->msg_iter, flags & MSG_DONTWAIT, skb);
        if (ret > (ssize_t)total_len) {
                m->msg_flags |= MSG_TRUNC;
                ret = flags & MSG_TRUNC ? ret : total_len;
@@ -1874,6 +1879,13 @@ static int tun_recvmsg(struct socket *so
 out:
        tun_put(tun);
        return ret;
+
+out_put_tun:
+       tun_put(tun);
+out_free_skb:
+       if (skb)
+               kfree_skb(skb);
+       return ret;
 }
 
 static int tun_peek_len(struct socket *sock)