| From | Ben Hutchings <> | Date | Thu, 28 Dec 2017 17:05:44 +0000 | Subject | [PATCH 3.16 180/204] vlan: fix a use-after-free in vlan_device_event() |
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3.16.52-rc1 review patch. If anyone has any objections, please let me know.
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From: Cong Wang <xiyou.wangcong@gmail.com>
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@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> [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- 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;
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