4.9-stable review patch. If anyone has any objections, please let me know.
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From: Cong Wang xiyou.wangcong@gmail.com
[ Upstream commit 052d41c01b3a2e3371d66de569717353af489d63 ]
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/8021q/vlan.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/net/8021q/vlan.c +++ b/net/8021q/vlan.c @@ -376,6 +376,9 @@ static int vlan_device_event(struct noti 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 noti 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;