tun: free skb in early errors

BugLink: https://bugs.launchpad.net/bugs/1738975
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 <wexu@redhat.com>
Reported-by: Matthew Rosato <mjrosato@linux.vnet.ibm.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit c33ee15b3820a03cf8229ba9415084197b827f8c 4.14.y)
Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index d1cb1ff83251af761b7263409faee09057189052..d58ae8ad0a4eaf51620efdf018d3f8cc5e867f90 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1519,8 +1519,11 @@ static ssize_t tun_do_read(struct tun_struct *tun, struct tun_file *tfile,
 
        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 */
@@ -1636,22 +1639,24 @@ static int tun_recvmsg(struct socket *sock, struct msghdr *m, size_t total_len,
 {
        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;
@@ -1659,6 +1664,13 @@ static int tun_recvmsg(struct socket *sock, struct msghdr *m, size_t total_len,
 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)