linux-hardening - Re: [PATCH 09/19] zonefs: remove duplicate cleanup in zonefs_fill

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Date:   Thu, 14 Sep 2023 01:49:00 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Christoph Hellwig <hch@....de>
Cc:     Christian Brauner <brauner@...nel.org>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Dennis Dalessandro <dennis.dalessandro@...nelisnetworks.com>,
        Tejun Heo <tj@...nel.org>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Damien Le Moal <dlemoal@...nel.org>,
        Naohiro Aota <naohiro.aota@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-rdma@...r.kernel.org,
        linux-nfs@...r.kernel.org, linux-hardening@...r.kernel.org,
        cgroups@...r.kernel.org
Subject: Re: [PATCH 09/19] zonefs: remove duplicate cleanup in
 zonefs_fill_super

On Wed, Sep 13, 2023 at 08:10:03AM -0300, Christoph Hellwig wrote:
> When ->fill_super fails, ->kill_sb is called which already cleans up
> the inodes and zgroups.

Ugh...  The use of "->" strongly suggests that you are talking about
a method; 'fill_super' here actually refers to callback passed to
mount_bdev().  Have a pity for those who'll be trying to parse it
- that might be yourself a couple of years down the road...

Something like

"If zonefs_fill_super() returns an error, its caller (mount_bdev()) will
make sure to call zonefs_kill_super(), which already cleans up
the inodes and zgroups.", perhaps?

> 
> Drop the extra cleanup code in zonefs_fill_super.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  fs/zonefs/super.c | 21 +++++----------------
>  1 file changed, 5 insertions(+), 16 deletions(-)
> 
> diff --git a/fs/zonefs/super.c b/fs/zonefs/super.c
> index 9d1a9808fbbba6..35b2554ce2ac2e 100644
> --- a/fs/zonefs/super.c
> +++ b/fs/zonefs/super.c
> @@ -1309,13 +1309,12 @@ static int zonefs_fill_super(struct super_block *sb, void *data, int silent)
>  	/* Initialize the zone groups */
>  	ret = zonefs_init_zgroups(sb);
>  	if (ret)
> -		goto cleanup;
> +		return ret;
>  
>  	/* Create the root directory inode */
> -	ret = -ENOMEM;
>  	inode = new_inode(sb);
>  	if (!inode)
> -		goto cleanup;
> +		return -ENOMEM;
>  
>  	inode->i_ino = bdev_nr_zones(sb->s_bdev);
>  	inode->i_mode = S_IFDIR | 0555;
> @@ -1333,7 +1332,7 @@ static int zonefs_fill_super(struct super_block *sb, void *data, int silent)
>  
>  	sb->s_root = d_make_root(inode);
>  	if (!sb->s_root)
> -		goto cleanup;
> +		return -ENOMEM;
>  
>  	/*
>  	 * Take a reference on the zone groups directory inodes
> @@ -1341,19 +1340,9 @@ static int zonefs_fill_super(struct super_block *sb, void *data, int silent)
>  	 */
>  	ret = zonefs_get_zgroup_inodes(sb);
>  	if (ret)
> -		goto cleanup;
> -
> -	ret = zonefs_sysfs_register(sb);
> -	if (ret)
> -		goto cleanup;
> -
> -	return 0;
> -
> -cleanup:
> -	zonefs_release_zgroup_inodes(sb);
> -	zonefs_free_zgroups(sb);
> +		return ret;
>  
> -	return ret;
> +	return zonefs_sysfs_register(sb);
>  }
>  
>  static struct dentry *zonefs_mount(struct file_system_type *fs_type,
> -- 
> 2.39.2
>