vlan: fix a use-after-free in vlan_device_event()

After refcnt reaches zero, vlan_vid_del() could free
dev->vlan_info via RCU:

	RCU_INIT_POINTER(dev->vlan_info, NULL);
	call_rcu(&vlan_info->rcu, vlan_info_rcu_free);

However, the pointer 'grp' still points to that memory
since it is set before vlan_vid_del():

        vlan_info = rtnl_dereference(dev->vlan_info);
        if (!vlan_info)
                goto out;
        grp = &vlan_info->grp;

Depends on when that RCU callback is scheduled, we could
trigger a use-after-free in vlan_group_for_each_dev()
right following this vlan_vid_del().

Fix it by moving vlan_vid_del() before setting grp. This
is also symmetric to the vlan_vid_add() we call in
vlan_device_event().

Reported-by: Fengguang Wu <[email protected]>
Fixes: efc73f4bbc23 ("net: Fix memory leak - vlan_info struct")
Cc: Alexander Duyck <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Girish Moodalbail <[email protected]>
Signed-off-by: Cong Wang <[email protected]>
Reviewed-by: Girish Moodalbail <[email protected]>
Tested-by: Fengguang Wu <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

0 files changed, 0 insertions, 0 deletions