3.16.52-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Cong Wang <xiyou.wangcong@xxxxxxxxx>
commit 052d41c01b3a2e3371d66de569717353af489d63 upstream.
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@xxxxxxxxx>
Fixes: efc73f4bbc23 ("net: Fix memory leak - vlan_info struct")
Cc: Alexander Duyck <alexander.duyck@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Girish Moodalbail <girish.moodalbail@xxxxxxxxxx>
Signed-off-by: Cong Wang <xiyou.wangcong@xxxxxxxxx>
Reviewed-by: Girish Moodalbail <girish.moodalbail@xxxxxxxxxx>
Tested-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
net/8021q/vlan.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/net/8021q/vlan.c
+++ b/net/8021q/vlan.c
@@ -364,6 +364,9 @@ 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)
@@ -408,9 +411,6 @@ static int vlan_device_event(struct noti
break;
case NETDEV_DOWN:
- 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;