diff options
authorCong Wang <xiyou.wangcong@gmail.com>2017-11-09 16:43:13 -0800
committerDavid S. Miller <davem@davemloft.net>2017-11-11 19:35:32 +0900
commit052d41c01b3a2e3371d66de569717353af489d63 (patch)
parent2118df93b5e1742931da358c2b8804c46fd64490 (diff)
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 <fengguang.wu@intel.com> Fixes: efc73f4bbc23 ("net: Fix memory leak - vlan_info struct") Cc: Alexander Duyck <alexander.duyck@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Girish Moodalbail <girish.moodalbail@oracle.com> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com> Reviewed-by: Girish Moodalbail <girish.moodalbail@oracle.com> Tested-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
1 files 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,
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;
- 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;

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