net-2.6 : V2 - fix dev_get_valid_name

the commit:

commit d90310243fd750240755e217c5faa13e24f41536
Author: Octavian Purdila <opurdila@ixiacom.com>
Date:   Wed Nov 18 02:36:59 2009 +0000

    net: device name allocation cleanups

introduced a bug when there is a hash collision making impossible
to rename a device with eth%d. This bug is very hard to reproduce
and appears rarely.

The problem is coming from we don't pass a temporary buffer to
__dev_alloc_name but 'dev->name' which is modified by the function.

A detailed explanation is here:

http://marc.info/?l=linux-netdev&m=127417784011987&w=2

Changelog:
 V2 : replaced strings comparison by pointers comparison

Signed-off-by: Daniel Lezcano <daniel.lezcano@free.fr>
Reviewed-by: Octavian Purdila <opurdila@ixiacom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 8 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 0aab66d68b1..07a48e2bf7d 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -954,18 +954,22 @@ int dev_alloc_name(struct net_device *dev, const char *name)
 }
 EXPORT_SYMBOL(dev_alloc_name);
 
-static int dev_get_valid_name(struct net *net, const char *name, char *buf,
-                              bool fmt)
+static int dev_get_valid_name(struct net_device *dev, const char *name, bool fmt)
 {
+        struct net *net;
+
+        BUG_ON(!dev_net(dev));
+        net = dev_net(dev);
+
         if (!dev_valid_name(name))
                 return -EINVAL;
 
         if (fmt && strchr(name, '%'))
-                return __dev_alloc_name(net, name, buf);
+                return dev_alloc_name(dev, name);
         else if (__dev_get_by_name(net, name))
                 return -EEXIST;
-        else if (buf != name)
-                strlcpy(buf, name, IFNAMSIZ);
+        else if (dev->name != name)
+                strlcpy(dev->name, name, IFNAMSIZ);
 
         return 0;
 }
@@ -997,7 +1001,7 @@ int dev_change_name(struct net_device *dev, const char *newname)
 
         memcpy(oldname, dev->name, IFNAMSIZ);
 
-        err = dev_get_valid_name(net, newname, dev->name, 1);
+        err = dev_get_valid_name(dev, newname, 1);
         if (err < 0)
                 return err;
 
@@ -4965,7 +4969,7 @@ int register_netdevice(struct net_device *dev)
                 }
         }
 
-        ret = dev_get_valid_name(net, dev->name, dev->name, 0);
+        ret = dev_get_valid_name(dev, dev->name, 0);
         if (ret)
                 goto err_uninit;
 
@@ -5574,7 +5578,7 @@ int dev_change_net_namespace(struct net_device *dev, struct net *net, const char
                 /* We get here if we can't use the current device name */
                 if (!pat)
                         goto out;
-                if (dev_get_valid_name(net, pat, dev->name, 1))
+                if (dev_get_valid_name(dev, pat, 1))
                         goto out;
         }