[PATCH] net: Fix userspace RTM_NEWLINK notifications.

[PATCH] net: Fix userspace RTM_NEWLINK notifications.

[Eric W. Biederman]

I received some bug reports about userspace programs having problems
because after RTM_NEWLINK was received they could not immediate access
files under /proc/sys/net/ because they had not been registered yet.

The original problem was trivially fixed by moving the userspace
notification from rtnetlink_event() to the end of
register_netdevice().

When testing that change I discovered I was still getting RTM_NEWLINK
events before I could access proc and I was also getting RTM_NEWLINK
events after I was seeing RTM_DELLINK.  Things practically guaranteed
to confuse userspace.

After a little more investigation these extra notifications proved to
be from the new notifiers NETDEV_POST_INIT and NETDEV_UNREGISTER_BATCH
hitting the default case in rtnetlink_event, and triggering
unnecessary RTM_NEWLINK messages.

rtnetlink_event now explicitly handles NETDEV_UNREGISTER_BATCH and
NETDEV_POST_INIT to avoid sending the incorrect userspace
notifications.

Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
---
 net/core/dev.c       |   11 +++++++++++
 net/core/rtnetlink.c |    6 +++---
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index c36a17a..369e83a 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5033,6 +5033,11 @@ int register_netdevice(struct net_device *dev)
 		rollback_registered(dev);
 		dev->reg_state = NETREG_UNREGISTERED;
 	}
+	/*
+	 *	Prevent userspace races by waiting until the network
+	 *	device is fully setup before sending notifications.
+	 */
+	rtmsg_ifinfo(RTM_NEWLINK, dev, ~0U);
 
 out:
 	return ret;
@@ -5595,6 +5600,12 @@ int dev_change_net_namespace(struct net_device *dev, struct net *net, const char
 	/* Notify protocols, that a new device appeared. */
 	call_netdevice_notifiers(NETDEV_REGISTER, dev);
 
+	/*
+	 *	Prevent userspace races by waiting until the network
+	 *	device is fully setup before sending notifications.
+	 */
+	rtmsg_ifinfo(RTM_NEWLINK, dev, ~0U);
+
 	synchronize_net();
 	err = 0;
 out:
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 33148a5..794bcb8 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1364,15 +1364,15 @@ static int rtnetlink_event(struct notifier_block *this, unsigned long event, voi
 	case NETDEV_UNREGISTER:
 		rtmsg_ifinfo(RTM_DELLINK, dev, ~0U);
 		break;
-	case NETDEV_REGISTER:
-		rtmsg_ifinfo(RTM_NEWLINK, dev, ~0U);
-		break;
 	case NETDEV_UP:
 	case NETDEV_DOWN:
 		rtmsg_ifinfo(RTM_NEWLINK, dev, IFF_UP|IFF_RUNNING);
 		break;
+	case NETDEV_POST_INIT:
+	case NETDEV_REGISTER:
 	case NETDEV_CHANGE:
 	case NETDEV_GOING_DOWN:
+	case NETDEV_UNREGISTER_BATCH:
 		break;
 	default:
 		rtmsg_ifinfo(RTM_NEWLINK, dev, 0);
-- 
1.6.5.2.143.g8cc62

Re: [PATCH] net: Fix userspace RTM_NEWLINK notifications.

[Marcel Holtmann]

Hi Eric,

> I received some bug reports about userspace programs having problems
> because after RTM_NEWLINK was received they could not immediate access
> files under /proc/sys/net/ because they had not been registered yet.
> 
> The original problem was trivially fixed by moving the userspace
> notification from rtnetlink_event() to the end of
> register_netdevice().
> 
> When testing that change I discovered I was still getting RTM_NEWLINK
> events before I could access proc and I was also getting RTM_NEWLINK
> events after I was seeing RTM_DELLINK.  Things practically guaranteed
> to confuse userspace.
> 
> After a little more investigation these extra notifications proved to
> be from the new notifiers NETDEV_POST_INIT and NETDEV_UNREGISTER_BATCH
> hitting the default case in rtnetlink_event, and triggering
> unnecessary RTM_NEWLINK messages.
> 
> rtnetlink_event now explicitly handles NETDEV_UNREGISTER_BATCH and
> NETDEV_POST_INIT to avoid sending the incorrect userspace
> notifications.

the POST_INIT and UNREGISTER_BATCH are not 2.6.32 features. They are
2.6.33 features and thus you need to create a separate patch for -stable
if you wanna fix the /proc access issue.

Regards

Marcel

Re: [PATCH] net: Fix userspace RTM_NEWLINK notifications.

[David Miller]

From: ebiederm@xmission.com (Eric W. Biederman)
Date: Sun, 13 Dec 2009 00:11:15 -0800

> 
> I received some bug reports about userspace programs having problems
> because after RTM_NEWLINK was received they could not immediate access
> files under /proc/sys/net/ because they had not been registered yet.
 ...
> Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>

Applied, thanks Eric.

Re: [PATCH] net: Fix userspace RTM_NEWLINK notifications.

[David Miller]

From: Marcel Holtmann <marcel@holtmann.org>
Date: Mon, 14 Dec 2009 03:05:36 +0100

> the POST_INIT and UNREGISTER_BATCH are not 2.6.32 features. They are
> 2.6.33 features and thus you need to create a separate patch for -stable
> if you wanna fix the /proc access issue.

Eric, please give me a suitable backport for -stable.

Thanks.

[PATCH v2.6.32] net: Fix userspace RTM_NEWLINK notifications.

[Eric W. Biederman]

I received some bug reports about userspace programs having problems
because after RTM_NEWLINK was received they could not immeidate
access files under /proc/sys/net/ because they had not been
registered yet.

The problem was trivailly fixed by moving the userspace
notification from rtnetlink_event to the end of register_netdevice.

Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
---

This patch is against 2.6.32 and should work back to 2.6.29 and
probably earlier.

 net/core/dev.c       |   11 +++++++++++
 net/core/rtnetlink.c |    4 +---
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index fe10551..584046e 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4860,6 +4860,11 @@ int register_netdevice(struct net_device *dev)
 		rollback_registered(dev);
 		dev->reg_state = NETREG_UNREGISTERED;
 	}
+	/*
+	 *	Prevent userspace races by waiting until the network
+	 *	device is fully setup before sending notifications.
+	 */
+	rtmsg_ifinfo(RTM_NEWLINK, dev, ~0U);
 
 out:
 	return ret;
@@ -5398,6 +5403,12 @@ int dev_change_net_namespace(struct net_device *dev, struct net *net, const char
 	/* Notify protocols, that a new device appeared. */
 	call_netdevice_notifiers(NETDEV_REGISTER, dev);
 
+	/*
+	 *	Prevent userspace races by waiting until the network
+	 *	device is fully setup before sending notifications.
+	 */
+	rtmsg_ifinfo(RTM_NEWLINK, dev, ~0U);
+
 	synchronize_net();
 	err = 0;
 out:
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index eb42873..d4fd895 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1334,13 +1334,11 @@ static int rtnetlink_event(struct notifier_block *this, unsigned long event, voi
 	case NETDEV_UNREGISTER:
 		rtmsg_ifinfo(RTM_DELLINK, dev, ~0U);
 		break;
-	case NETDEV_REGISTER:
-		rtmsg_ifinfo(RTM_NEWLINK, dev, ~0U);
-		break;
 	case NETDEV_UP:
 	case NETDEV_DOWN:
 		rtmsg_ifinfo(RTM_NEWLINK, dev, IFF_UP|IFF_RUNNING);
 		break;
+	case NETDEV_REGISTER:
 	case NETDEV_CHANGE:
 	case NETDEV_GOING_DOWN:
 		break;
-- 
1.6.5.2.143.g8cc62