linux-kernel - Re: [PATCH] drivers: base: core: do not put noninitialized devices

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Date:	Fri, 19 Nov 2010 12:57:09 -0800
From:	Greg KH <gregkh@...e.de>
To:	Vasiliy Kulikov <segoon@...nwall.com>
Cc:	kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers: base: core: do not put noninitialized devices

On Fri, Nov 19, 2010 at 10:14:25PM +0300, Vasiliy Kulikov wrote:
> Hi Greg,
> 
> On Fri, Nov 19, 2010 at 11:02 -0800, Greg KH wrote:
> > On Fri, Nov 19, 2010 at 09:41:40PM +0300, Vasiliy Kulikov wrote:
> > > If kobject_set_name_vargs() fails then put_device() frees
> > > device with zero kobj->state_initialized.  This leads to WARN().
> > 
> > Have you seen this happen?
> 
> No, I've just analized the code.  Without device_initialize() ->kobj is
> not initialized:
> 
> 	kobject_init(&dev->kobj, &device_ktype) calls
> 
> 	kobject_init_internal(kobj) calls
> 
> 	kobj->state_initialized = 1;
> 
> kobject_put() calls WARN if state_initialized == 0:
> 
>     void kobject_put(struct kobject *kobj)
>     {
>         if (kobj) {
>             if (!kobj->state_initialized)
>                 WARN(1, KERN_WARNING "kobject: '%s' (%p): is not "
>                        "initialized, yet kobject_put() is being "
>                        "called.\n", kobject_name(kobj), kobj);
> 
> 
> I got the stack dump with similar code:
> 
>     struct device *dev = kzalloc(sizeof(*dev), GFP_KERNEL);
>     put_device(dev);

Sure, that's illegal code, and we want to warn about that.  So I would
say, if an error happens, we want to see this message so the code should
stay as-is.

thanks,

greg k-h
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