linux-kernel - Re: [PATCH] ovl: tentative fix for broken vfs

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Message-ID: <20161128110609.GB27319@chrystal.oracle.com>
Date:   Mon, 28 Nov 2016 12:06:09 +0100
From:   Quentin Casasnovas <quentin.casasnovas@...cle.com>
To:     Miklos Szeredi <miklos@...redi.hu>
Cc:     Quentin Casasnovas <quentin.casasnovas@...cle.com>,
        linux-kernel@...r.kernel.org, linux-unionfs@...r.kernel.org,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH] ovl: tentative fix for broken vfs_open() on stacked
 overlayfs.

On Mon, Nov 28, 2016 at 10:45:18AM +0100, Miklos Szeredi wrote:
> On Fri, Nov 25, 2016 at 08:28:47PM +0100, Quentin Casasnovas wrote:
> > On Fri, Nov 25, 2016 at 06:09:23PM +0100, Quentin Casasnovas wrote:
> > > If two overlayfs filesystems are stacked on top of each other, then we need
> > > to recurse when opening a file.  This used to work and was first broken by:
> > > 
> > >   4bacc9c9234c ("overlayfs: Make f_path always point to the overlay...")
> > > 
> > > and fixed by:
> > > 
> > >   1c8a47df36d7 ("ovl: fix open in stacked overlay")
> > > 
> > > But it looks like it was re-introduced in:
> > > 
> > >   2d902671ce1c ("vfs: merge .d_select_inode() into .d_real()")
> 
> 
> Following patch should fix it (it's there in your patch, so you weren't too far
> off).  It needs more testing and review, but I think it fixes the basic problem.
> 
> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
> index edd46a0e951d..f4d2f63fa53a 100644
> --- a/fs/overlayfs/super.c
> +++ b/fs/overlayfs/super.c
> @@ -328,7 +328,7 @@ static struct dentry *ovl_d_real(struct dentry *dentry,
>  	if (!real)
>  		goto bug;
>  
> -	if (!inode || inode == d_inode(real))
> +	if (inode && inode == d_inode(real))
>  		return real;
>  
>  	/* Handle recursion */

The above patch works for me, thanks!

Tested-by: Quentin Casasnovas <quentin.casasnovas@...cle.com>

Q

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