tap: double-free in error path in tap_open()

BugLink: http://bugs.launchpad.net/bugs/1744121
[ Upstream commit 78e0ea6791d7baafb8a0ca82b1bd0c7b3453c919 ]

Double free of skb_array in tap module is causing kernel panic. When
tap_set_queue() fails we free skb_array right away by calling
skb_array_cleanup(). However, later on skb_array_cleanup() is called
again by tap_sock_destruct through sock_put(). This patch fixes that
issue.

Fixes: 362899b8725b35e3 (macvtap: switch to use skb array)
Signed-off-by: Girish Moodalbail <girish.moodalbail@oracle.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index 7a2f6bebfd1527529e1383114b7d7455e875660d..f7ade1df963a41cc096aa92cb2a20370d97b8ae1 100644 (file)
--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -517,6 +517,10 @@ static int tap_open(struct inode *inode, struct file *file)
                                             &tap_proto, 0);
        if (!q)
                goto err;
+       if (skb_array_init(&q->skb_array, tap->dev->tx_queue_len, GFP_KERNEL)) {
+               sk_free(&q->sk);
+               goto err;
+       }
 
        RCU_INIT_POINTER(q->sock.wq, &q->wq);
        init_waitqueue_head(&q->wq.wait);
@@ -540,22 +544,18 @@ static int tap_open(struct inode *inode, struct file *file)
        if ((tap->dev->features & NETIF_F_HIGHDMA) && (tap->dev->features & NETIF_F_SG))
                sock_set_flag(&q->sk, SOCK_ZEROCOPY);
 
-       err = -ENOMEM;
-       if (skb_array_init(&q->skb_array, tap->dev->tx_queue_len, GFP_KERNEL))
-               goto err_array;
-
        err = tap_set_queue(tap, file, q);
-       if (err)
-               goto err_queue;
+       if (err) {
+               /* tap_sock_destruct() will take care of freeing skb_array */
+               goto err_put;
+       }
 
        dev_put(tap->dev);
 
        rtnl_unlock();
        return err;
 
-err_queue:
-       skb_array_cleanup(&q->skb_array);
-err_array:
+err_put:
        sock_put(&q->sk);
 err:
        if (tap)