linux-kernel - Re: [PATCH] sysfs: kill an extra put in sysfs_create

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Message-ID: <20070718131646.2c9cdab0@gondolin.boeblingen.de.ibm.com>
Date:	Wed, 18 Jul 2007 13:16:46 +0200
From:	Cornelia Huck <cornelia.huck@...ibm.com>
To:	Tejun Heo <htejun@...il.com>
Cc:	Gabriel C <nix.or.die@...glemail.com>,
	Satyam Sharma <satyam.sharma@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Christoph Lameter <clameter@....com>, gregkh@...e.de,
	miles.lane@...il.com
Subject: Re: [PATCH] sysfs: kill an extra put in sysfs_create_link() failure
 path

On Wed, 18 Jul 2007 16:14:45 +0900,
Tejun Heo <htejun@...il.com> wrote:

> There is a subtle bug in sysfs_create_link() failure path.  When
> symlink creation fails because there's already a node with the same
> name, the target sysfs_dirent is put twice - once by failure path of
> sysfs_create_link() and once more when the symlink is released.
> 
> Fix it by making only the symlink node responsible for putting
> target_sd.
> 
> Signed-off-by: Tejun Heo <htejun@...il.com>
> ---
> Gabriel, Miles, please verify this fixes your problem.  Thanks.
> 
>  fs/sysfs/symlink.c |    2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
> index 2f86e04..d056e96 100644
> --- a/fs/sysfs/symlink.c
> +++ b/fs/sysfs/symlink.c
> @@ -86,7 +86,9 @@ int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char
>  	sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK);
>  	if (!sd)
>  		goto out_put;
> +
>  	sd->s_elem.symlink.target_sd = target_sd;
> +	target_sd = NULL;	/* reference is now owned by the symlink */
> 
>  	sysfs_addrm_start(&acxt, parent_sd);
> 

A subtle bug indeed. The patch looks sane to me.

Reviewed-by: Cornelia Huck <cornelia.huck@...ibm.com>
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