bonding: fix error handling if slave is busy (v2)

commit f7d9821a6a9c83450ac35e76d3709e32fd38b76f upstream.

If slave device already has a receive handler registered, then the
error unwind of bonding device enslave function is broken.

The following will leave a pointer to freed memory in the slave
device list, causing a later kernel panic.
# modprobe dummy
# ip li add dummy0-1 link dummy0 type macvlan
# modprobe bonding
# echo +dummy0 >/sys/class/net/bond0/bonding/slaves

The fix is to detach the slave (which removes it from the list)
in the unwind path.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Reviewed-by: Nicolas de Pesloüan <nicolas.2p.debian@free.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 7 insertions, 2 deletions

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 2065cb4002b..0b65c5fccc3 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1905,7 +1905,7 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
                                  "but new slave device does not support netpoll.\n",
                                  bond_dev->name);
                         res = -EBUSY;
-                        goto err_close;
+                        goto err_detach;
                 }
         }
 #endif
@@ -1914,7 +1914,7 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
 
         res = bond_create_slave_symlinks(bond_dev, slave_dev);
         if (res)
-                goto err_close;
+                goto err_detach;
 
         res = netdev_rx_handler_register(slave_dev, bond_handle_frame,
                                          new_slave);
@@ -1935,6 +1935,11 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
 err_dest_symlinks:
         bond_destroy_slave_symlinks(bond_dev, slave_dev);
 
+err_detach:
+        write_lock_bh(&bond->lock);
+        bond_detach_slave(bond, new_slave);
+        write_unlock_bh(&bond->lock);
+
 err_close:
         dev_close(slave_dev);