linux-kernel - Re: [PATCH] mnt: Move the clear of MNT_LOCKED from copy

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Message-ID: <20141008104649.GA24908@paralelels.com>
Date:	Wed, 8 Oct 2014 14:46:49 +0400
From:	Andrew Vagin <avagin@...allels.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Al Viro <viro@...IV.linux.org.uk>,
	Andrey Vagin <avagin@...nvz.org>,
	<linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Serge Hallyn <serge.hallyn@...onical.com>
Subject: Re: [PATCH] mnt: Move the clear of MNT_LOCKED from copy_tree to it's

On Tue, Oct 07, 2014 at 04:40:10PM -0700, Eric W. Biederman wrote:
> 
> Clear MNT_LOCKED in the callers of copy_tree except copy_mnt_ns, and
> collect_mounts.  In copy_mnt_nswe want an exact copy of a mount tree,
> so not clearing MNT_LOCKED is important.  Similarly collect_mounts
> is used to take a snapshot of the mount tree for audit logging purposes
> and auditing using a faithful copy of the tree is important.
> 
> This becomes particularly significant when we start setting MNT_LOCKED
> on rootfs to prevent it from being unmounted.
> 

Acked-by: Andrew Vagin <avagin@...allels.com>

> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
> ---
>  fs/namespace.c | 1 -
>  fs/pnode.c     | 1 +
>  2 files changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/namespace.c b/fs/namespace.c
> index 9c6ee037bef7..5a11e273541c 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -1498,7 +1498,6 @@ struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
>  	if (IS_ERR(q))
>  		return q;
>  
> -	q->mnt.mnt_flags &= ~MNT_LOCKED;
>  	q->mnt_mountpoint = mnt->mnt_mountpoint;
>  
>  	p = mnt;
> diff --git a/fs/pnode.c b/fs/pnode.c
> index aae331a5d03b..260ac8f898a4 100644
> --- a/fs/pnode.c
> +++ b/fs/pnode.c
> @@ -242,6 +242,7 @@ static int propagate_one(struct mount *m)
>  	child = copy_tree(last_source, last_source->mnt.mnt_root, type);
>  	if (IS_ERR(child))
>  		return PTR_ERR(child);
> +	child->mnt.mnt_flags &= ~MNT_LOCKED;
>  	mnt_set_mountpoint(m, mp, child);
>  	last_dest = m;
>  	last_source = child;
> -- 
> 1.9.1
> 
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