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 <fengguang...@intel.com>
Fixes: efc73f4bbc23 ("net: Fix memory leak - vlan_info struct")
Cc: Alexander Duyck <alexander.du...@gmail.com>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Girish Moodalbail <girish.moodalb...@oracle.com>
Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
---
net/8021q/vlan.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c
index 9649579b5b9f..4a72ee4e2ae9 100644
--- a/net/8021q/vlan.c
+++ b/net/8021q/vlan.c
@@ -376,6 +376,9 @@ static int vlan_device_event(struct notifier_block *unused,
unsigned long event,
dev->name);
vlan_vid_add(dev, htons(ETH_P_8021Q), 0);
}
+ if (event == NETDEV_DOWN &&
+ (dev->features & NETIF_F_HW_VLAN_CTAG_FILTER))
+ vlan_vid_del(dev, htons(ETH_P_8021Q), 0);
vlan_info = rtnl_dereference(dev->vlan_info);
if (!vlan_info)
@@ -423,9 +426,6 @@ static int vlan_device_event(struct notifier_block *unused,
unsigned long event,
struct net_device *tmp;
LIST_HEAD(close_list);
- if (dev->features & NETIF_F_HW_VLAN_CTAG_FILTER)
- vlan_vid_del(dev, htons(ETH_P_8021Q), 0);
-
/* Put all VLANs for this dev in the down state too. */
vlan_group_for_each_dev(grp, i, vlandev) {
flgs = vlandev->flags;
--
2.13.0
