linux-kernel - Re: [PATCH] driver: make dev_set

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Date:	Tue, 28 Apr 2009 08:39:37 -0700
From:	Greg KH <gregkh@...e.de>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Kay Sievers <kay.sievers@...y.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH] driver: make dev_set_name(, NULL) work

On Tue, Apr 28, 2009 at 08:14:13AM -0700, Yinghai Lu wrote:
> Greg KH wrote:
> > On Tue, Apr 28, 2009 at 12:36:06AM -0700, Yinghai Lu wrote:
> >> while looking dev_set_name() calling, there is one
> >> 	dev_set_name(&dev->dev, NULL)
> >> to used to try to free the device name, before kfree that device.
> > 
> > What's wrong with that?
> > 
> >> need to move the check for device_add in
> >> | commit 8a577ffc75d9194fe8cdb7479236f2081c26ca1f
> >> | Author: Kay Sievers <kay.sievers@...y.org>
> >> | Date:   Sat Apr 18 15:05:45 2009 -0700
> >> |
> >> |    driver: dont update dev_name via device_add path
> >> from kobject_set_name_vargs to kobject_add_vargs instead.
> >>
> >> in kobject_set_name_vargs will check if fmt is NULL.
> >>
> >> actually we need to use dev_set_name(,NULL) later on failing path
> >> and release to prevent leaking
> > 
> > Are you sure?
> > 
> > confused,
> > 
> 
> in arch/arm/common/sa111.c
> 
> 
> static int
> sa1111_init_one_child(struct sa1111 *sachip, struct resource *parent,
>                       struct sa1111_dev_info *info)
> {
>         struct sa1111_dev *dev;
>         int ret;
> 
>         dev = kzalloc(sizeof(struct sa1111_dev), GFP_KERNEL);
>         if (!dev) {
>                 ret = -ENOMEM;
>                 goto out;
>         }
> 
>         dev_set_name(&dev->dev, "%4.4lx", info->offset);
>         dev->devid       = info->devid;
>         dev->dev.parent  = sachip->dev;
>         dev->dev.bus     = &sa1111_bus_type;
>         dev->dev.release = sa1111_dev_release;
>         dev->dev.coherent_dma_mask = sachip->dev->coherent_dma_mask;
>         dev->res.start   = sachip->phys + info->offset;
>         dev->res.end     = dev->res.start + 511;
>         dev->res.name    = dev_name(&dev->dev);
>         dev->res.flags   = IORESOURCE_MEM;
>         dev->mapbase     = sachip->base + info->offset;
>         dev->skpcr_mask  = info->skpcr_mask;
>         memmove(dev->irq, info->irq, sizeof(dev->irq));
> 
>         ret = request_resource(parent, &dev->res);
>         if (ret) {
>                 printk("SA1111: failed to allocate resource for %s\n",
>                         dev->res.name);
>                 dev_set_name(&dev->dev, NULL);
>                 kfree(dev);
>                 goto out;
>         }
> 
> 
> when first dev_set_name is called, dev->dev.kobj.name will initialized from kmalloc.
> so before kfree(dev), do we need to kfree that name?

Do a "put_device()" instead, and everything will be freed.

thanks,

greg k-h
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