linux-kernel - Re: [PATCH 1/1] gfs2: incorrect check for debugfs returns

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Date:	Tue, 24 Mar 2015 10:21:21 +0000
From:	Steven Whitehouse <swhiteho@...hat.com>
To:	Chengyu Song <csong84@...ech.edu>, cluster-devel@...hat.com,
	linux-kernel@...r.kernel.org
CC:	taesoo@...ech.edu, changwoo@...ech.edu, sanidhya@...ech.edu,
	blee@...ech.edu
Subject: Re: [PATCH 1/1] gfs2: incorrect check for debugfs returns

Hi,

On 24/03/15 02:36, Chengyu Song wrote:
> debugfs_create_dir and debugfs_create_file may return -ENODEV when debugfs
> is not configured, so the return value should be checked against ERROR_VALUE
> as well, otherwise the later dereference of the dentry pointer would crash
> the kernel.
Looks reasonable to me:

Acked-by: Steven Whitehouse <swhiteho@...hat.com>

Steve.

> Signed-off-by: Chengyu Song <csong84@...ech.edu>
> ---
>   fs/gfs2/glock.c | 47 ++++++++++++++++++++++++++++-------------------
>   1 file changed, 28 insertions(+), 19 deletions(-)
>
> diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
> index f42dffb..0fa8062 100644
> --- a/fs/gfs2/glock.c
> +++ b/fs/gfs2/glock.c
> @@ -2047,34 +2047,41 @@ static const struct file_operations gfs2_sbstats_fops = {
>   
>   int gfs2_create_debugfs_file(struct gfs2_sbd *sdp)
>   {
> -	sdp->debugfs_dir = debugfs_create_dir(sdp->sd_table_name, gfs2_root);
> -	if (!sdp->debugfs_dir)
> -		return -ENOMEM;
> -	sdp->debugfs_dentry_glocks = debugfs_create_file("glocks",
> -							 S_IFREG | S_IRUGO,
> -							 sdp->debugfs_dir, sdp,
> -							 &gfs2_glocks_fops);
> -	if (!sdp->debugfs_dentry_glocks)
> +	struct dentry *dent;
> +
> +	dent = debugfs_create_dir(sdp->sd_table_name, gfs2_root);
> +	if (IS_ERR_OR_NULL(dent))
> +		goto fail;
> +	sdp->debugfs_dir = dent;
> +
> +	dent = debugfs_create_file("glocks",
> +				   S_IFREG | S_IRUGO,
> +				   sdp->debugfs_dir, sdp,
> +				   &gfs2_glocks_fops);
> +	if (IS_ERR_OR_NULL(dent))
>   		goto fail;
> +	sdp->debugfs_dentry_glocks = dent;
>   
> -	sdp->debugfs_dentry_glstats = debugfs_create_file("glstats",
> -							S_IFREG | S_IRUGO,
> -							sdp->debugfs_dir, sdp,
> -							&gfs2_glstats_fops);
> -	if (!sdp->debugfs_dentry_glstats)
> +	dent = debugfs_create_file("glstats",
> +				   S_IFREG | S_IRUGO,
> +				   sdp->debugfs_dir, sdp,
> +				   &gfs2_glstats_fops);
> +	if (IS_ERR_OR_NULL(dent))
>   		goto fail;
> +	sdp->debugfs_dentry_glstats = dent;
>   
> -	sdp->debugfs_dentry_sbstats = debugfs_create_file("sbstats",
> -							S_IFREG | S_IRUGO,
> -							sdp->debugfs_dir, sdp,
> -							&gfs2_sbstats_fops);
> -	if (!sdp->debugfs_dentry_sbstats)
> +	dent = debugfs_create_file("sbstats",
> +				   S_IFREG | S_IRUGO,
> +				   sdp->debugfs_dir, sdp,
> +				   &gfs2_sbstats_fops);
> +	if (IS_ERR_OR_NULL(dent))
>   		goto fail;
> +	sdp->debugfs_dentry_sbstats = dent;
>   
>   	return 0;
>   fail:
>   	gfs2_delete_debugfs_file(sdp);
> -	return -ENOMEM;
> +	return dent ? PTR_ERR(dent) : -ENOMEM;
>   }
>   
>   void gfs2_delete_debugfs_file(struct gfs2_sbd *sdp)
> @@ -2100,6 +2107,8 @@ void gfs2_delete_debugfs_file(struct gfs2_sbd *sdp)
>   int gfs2_register_debugfs(void)
>   {
>   	gfs2_root = debugfs_create_dir("gfs2", NULL);
> +	if (IS_ERR(gfs2_root))
> +		return PTR_ERR(gfs2_root);
>   	return gfs2_root ? 0 : -ENOMEM;
>   }
>   

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