[PATCH net v2 0/1] NULL pointer dereference in ipvlan_port_destroy

[Girish Moodalbail <girish.moodalbail@oracle.com>]

>From code inspection it appeared that there is a possibility where in
ipvlan_port_destroy() might be dealing with a port (struct ipvl_port)
that has already been destroyed and is therefore already NULL. However,
we don't check for NULL and continue to access the fields which results
in a kernel panic.

When call to register_netdevice() (called from ipvlan_link_new()) fails,
inside that function we call ipvlan_uninit() (through ndo_uninit()) to
destroy the ipvlan port. Upon returning unsuccessfully from
register_netdevice() we go ahead and call ipvlan_port_destroy() again
which causes NULL pointer dereference panic.

To test this theory, I loaded up netdev-notifier-error-inject.ko and did 

$ sudo echo -22 > /sys/kernel/debug/notifier-error-inject/\
  netdev/actions/NETDEV_POST_INIT/error
$ sudo  ip li add ipvl0 link enp7s0 type ipvlan
...system panics...
BUG: unable to handle kernel NULL pointer dereference at 0000000000000820
IP: ipvlan_port_destroy+0x2a/0xf0 [ipvlan]

Similar issue exists in macvlan_port_destroy() and it will be addressed
by a separate patch. The following patch fixes the ipvlan case. I tested
my changes for regression by running LTP's ipvlan test case.

Girish Moodalbail (1):
  ipvlan: NULL pointer dereference panic in ipvlan_port_destroy

 drivers/net/ipvlan/ipvlan_main.c | 104 +++++++++++++++++++++------------------
 1 file changed, 55 insertions(+), 49 deletions(-)

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1.8.3.1