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: efc73f4bbc ("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]>
Cong Wang
052d41c01b