linux-kernel - Re: [PATCH 4.4 06/34] sget(): handle failures of register

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Date:   Wed, 07 Mar 2018 02:16:51 +0000
From:   Ben Hutchings <ben.hutchings@...ethink.co.uk>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     stable@...r.kernel.org,
        Sasha Levin <alexander.levin@...rosoft.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4.4 06/34] sget(): handle failures of register_shrinker()

On Fri, 2018-03-02 at 09:51 +0100, Greg Kroah-Hartman wrote:
> 4.4-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Al Viro <viro@...iv.linux.org.uk>
> 
> 
> [ Upstream commit 9ee332d99e4d5a97548943b81c54668450ce641b ]
> 
> Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
> Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> ---
>  fs/super.c |    6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -497,7 +497,11 @@ retry:
>  	hlist_add_head(&s->s_instances, &type->fs_supers);
>  	spin_unlock(&sb_lock);
>  	get_filesystem(type);
> -	register_shrinker(&s->s_shrink);
> +	err = register_shrinker(&s->s_shrink);
> +	if (err) {
> +		deactivate_locked_super(s);

But deactivate_locked_super() will call unregister_shrinker(), which
doesn't look safe if register_shrinker() failed.

Ben.

> +		s = ERR_PTR(err);
> +	}
>  	return s;
>  }
>  
> 
> 
> 
-- 
Ben Hutchings
Software Developer, Codethink Ltd.