[PATCH v3 2/2] net: postpone net device uevent to fix a race

From: Kalle Valo
Date: Mon May 16 2011 - 10:57:42 EST

From: Kalle Valo <kalle.valo@xxxxxxxxxxx>

There's a race in register_netdevice() so that the udev 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

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

The issue is reported here:


Fix this by postponing the uevent with device_add_noevent() and
calling device_uevent() once the device is really ready.

Thanks to Johannes Berg for the original idea.

Signed-off-by: Kalle Valo <kalle.valo@xxxxxxxxxxx>
net/core/dev.c | 3 +++
net/core/net-sysfs.c | 2 +-
2 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 856b6ee..80cfa23 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5454,6 +5454,9 @@ int register_netdevice(struct net_device *dev)
dev->reg_state = NETREG_UNREGISTERED;
+ device_uevent(&(dev->dev));
* Prevent userspace races by waiting until the network
* device is fully setup before sending notifications.
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 5ceb257..c10b1d5 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -1337,7 +1337,7 @@ int netdev_register_kobject(struct net_device *net)
#endif /* CONFIG_SYSFS */

- error = device_add(dev);
+ error = device_add_noevent(dev);
if (error)
return error;

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