linux-kernel - Re: [-mm3 patch]Warning fix: check the return value of kobject

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Date:	Sat, 31 Mar 2007 22:31:36 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Cong WANG" <xiyou.wangcong@...il.com>
Cc:	linux-kernel@...r.kernel.org, viro@...iv.linux.org.uk
Subject: Re: [-mm3 patch]Warning fix: check the return value of kobject_add
 etc.

On Sat, 31 Mar 2007 10:30:31 +0800 "Cong WANG" <xiyou.wangcong@...il.com> wrote:

> Since kobject_add, sysfs_create_link and sysfs_create_file are marked
> as '__must_check', so we must always check their return values, or gcc
> will give us warnings.
> 
> Signed-off-by: Cong WANG <xiyou.wangcong@...il.com>
> 
> ---
> --- fs/partitions/check.c.orig	2007-03-30 21:35:45.000000000 +0800
> +++ fs/partitions/check.c	2007-03-30 21:49:53.000000000 +0800
> @@ -385,10 +385,16 @@ void add_partition(struct gendisk *disk,
>  	p->kobj.parent = &disk->kobj;
>  	p->kobj.ktype = &ktype_part;
>  	kobject_init(&p->kobj);
> -	kobject_add(&p->kobj);
> +	if (kobject_add(&p->kobj)) {
> +		kfree(p);
> +		return;
> +	}
>  	if (!disk->part_uevent_suppress)
>  		kobject_uevent(&p->kobj, KOBJ_ADD);
> -	sysfs_create_link(&p->kobj, &block_subsys.kset.kobj, "subsystem");
> +	if (sysfs_create_link(&p->kobj, &block_subsys.kset.kobj, "subsystem")) {
> +		kfree(p);
> +		return;
> +	}
>  	if (flags & ADDPART_FLAG_WHOLEDISK) {
>  		static struct attribute addpartattr = {
>  			.name = "whole_disk",
> @@ -396,7 +402,10 @@ void add_partition(struct gendisk *disk,
>  			.owner = THIS_MODULE,
>  		};
> 
> -		sysfs_create_file(&p->kobj, &addpartattr);
> +		if (sysfs_create_file(&p->kobj, &addpartattr)) {
> +			kfree(p);
> +			return;
> +		}
>  	}
>  	partition_sysfs_add_subdir(p);
>  	disk->part[part-1] = p;

Well yes, but the point here it to fix kernel bugs, not to just make the
warnings go away.

The bugs here are that the effects of the kobject_add() and the
sysfs_create_link() are not undone on the error path.

Also, please always prepare patches in `patch -p1' form, as per
http://www.zip.com.au/~akpm/linux/patches/stuff/tpp.txt, thanks.

-
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