From: Daniel Lezcano <daniel.lezcano@free•fr>
To: Octavian Purdila <opurdila@ixiacom•com>
Cc: Linux Netdev List <netdev@vger•kernel.org>
Subject: Re: dev_get_valid_name buggy with hash collision
Date: Tue, 18 May 2010 16:55:36 +0200 [thread overview]
Message-ID: <4BF2AA68.5090008@free.fr> (raw)
In-Reply-To: <201005181529.37420.opurdila@ixiacom.com>
On 05/18/2010 02:29 PM, Octavian Purdila wrote:
> On Tuesday 18 May 2010 13:17:10 you wrote:
>
>
>> 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
>>
>>
[ ... ]
>> --- net-2.6.orig/net/core/dev.c
>> +++ net-2.6/net/core/dev.c
>> @@ -936,18 +936,22 @@ int dev_alloc_name(struct net_device *de
>> }
>> 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 (strncmp(dev->name, name, IFNAMSIZ))
>> + strlcpy(dev->name, name, IFNAMSIZ);
>>
>>
> Why do the strncmp, can't we preserve the (buf != name) condition
The 'buf' parameter is no longer passed to the function. We have the
'dev' and the 'newname' parameters.
The pointer test was just to check 'dev_get_valid_name' was called from
the 'register_netdevice' function context with 'dev_get_valid_name(net,
dev->name, dev->name, 0)'. Comparing the strings is valid in this case.
Otherwise dev_get_valid_name is called from:
* "dev_change_net_namespace" with "dev%d" or "ifname" specified
within the netlink message. Both are different pointers, the first will
fall in the "if (fmt && strchr(name, '%'))".
* "dev_change_name", where the pointers are different and the strings
are different.
I think it is safe to do the string comparison here. But maybe there are
a few simplifications (eg. remove fmt) to do.
If you agree, I will send this patch against net-2.6 and the
simplifications against net-next-2.6.
Thanks
-- Daniel
next prev parent reply other threads:[~2010-05-18 14:55 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-18 10:17 dev_get_valid_name buggy with hash collision Daniel Lezcano
2010-05-18 12:29 ` Octavian Purdila
2010-05-18 14:55 ` Daniel Lezcano [this message]
2010-05-19 17:05 ` Octavian Purdila
2010-05-19 19:39 ` Daniel Lezcano
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