| Message ID | 20171110004313.20662-1-xiyou.wangcong@gmail.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
| Series | [net] vlan: fix a use-after-free in vlan_device_event() | expand |
On 11/9/17 4:43 PM, Cong Wang wrote: > 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> LGTM. Reviewed-by: Girish Moodalbail <girish.moodalbail@oracle.com> Thanks, ~Girish > --- > 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; >
It works, thank you for fixing this ancient bug!
Tested-by: Fengguang Wu <fengguang.wu@intel.com>
On Fri, Nov 10, 2017 at 3:50 AM, Fengguang Wu <fengguang.wu@intel.com> wrote: > It works, thank you for fixing this ancient bug! > > Tested-by: Fengguang Wu <fengguang.wu@intel.com> Thanks for all the 0day work to make people finally figure this out. Linus
From: Cong Wang <xiyou.wangcong@gmail.com> Date: Thu, 9 Nov 2017 16:43:13 -0800 > 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> Applied and queued up for -stable, thanks Cong!
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;
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> --- net/8021q/vlan.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)