netdev - [PATCH] net: fix rtnl even race in register

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Date:	Fri, 29 Apr 2011 20:26:34 +0300
From:	Kalle Valo <kvalo@...rom.com>
To:	netdev@...r.kernel.org
Cc:	linux-wireless@...r.kernel.org
Subject: [PATCH] net: fix rtnl even race in register_netdevice()

From: Kalle Valo <kalle.valo@...eros.com>

There's a race in register_netdevice so that the rtnl event is sent before
the device is actually ready. This was visible with flimflam, chrome os
connection manager:

00:21:35 roska flimflamd[2598]: src/udev.c:add_net_device()
00:21:35 roska flimflamd[2598]: connman_inet_ifname: SIOCGIFNAME(index
   4): No such device
00:21:45 roska flimflamd[2598]: src/rtnl.c:rtnl_message() buf
   0xbfefda3c len 1004
00:21:45 roska flimflamd[2598]: src/rtnl.c:rtnl_message()
   NEWLINK len 1004 type 16 flags 0x0000 seq 0

So the kobject is visible in udev before the device is ready.

(ignore the 10 s delay, I added that to reproduce the issue easily)

The issue is reported here:

https://bugzilla.kernel.org/show_bug.cgi?id=15606

The fix is to call netdev_register_kobject() after the device is added
to the list.

Signed-off-by: Kalle Valo <kalle.valo@...eros.com>
---
 net/core/dev.c |   10 +++++-----
 1 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 956d3b0..f2afbe6 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5425,11 +5425,6 @@ int register_netdevice(struct net_device *dev)
 	if (ret)
 		goto err_uninit;
 
-	ret = netdev_register_kobject(dev);
-	if (ret)
-		goto err_uninit;
-	dev->reg_state = NETREG_REGISTERED;
-
 	netdev_update_features(dev);
 
 	/*
@@ -5443,6 +5438,11 @@ int register_netdevice(struct net_device *dev)
 	dev_hold(dev);
 	list_netdevice(dev);
 
+	ret = netdev_register_kobject(dev);
+	if (ret)
+		goto err_uninit;
+	dev->reg_state = NETREG_REGISTERED;
+
 	/* Notify protocols, that a new device appeared. */
 	ret = call_netdevice_notifiers(NETDEV_REGISTER, dev);
 	ret = notifier_to_errno(ret);

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