linux-kernel - Re: [PATCH 4.4 29/49] nfs: Dont take a reference on fl->fl

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Date:   Sat, 9 Dec 2017 18:01:20 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Ben Hutchings <ben.hutchings@...ethink.co.uk>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Benjamin Coddington <bcodding@...hat.com>,
        Jeff Layton <jlayton@...hat.com>,
        Trond Myklebust <trond.myklebust@...marydata.com>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: Re: [PATCH 4.4 29/49] nfs: Dont take a reference on fl->fl_file for
 LOCK operation

On Fri, Dec 08, 2017 at 04:18:58AM +0000, Ben Hutchings wrote:
> On Thu, 2017-12-07 at 14:07 +0100, Greg Kroah-Hartman wrote:
> > 4.4-stable review patch.  If anyone has any objections, please let me know.
> > 
> > ------------------
> > 
> > From: Benjamin Coddington <bcodding@...hat.com>
> > 
> > 
> > [ Upstream commit 4b09ec4b14a168bf2c687e1f598140c3c11e9222 ]
> > 
> > I have reports of a crash that look like __fput() was called twice for
> > a NFSv4.0 file.  It seems possible that the state manager could try to
> > reclaim a lock and take a reference on the fl->fl_file at the same time the
> > file is being released if, during the close(), a signal interrupts the wait
> > for outstanding IO while removing locks which then skips the removal
> > of that lock.
> > 
> > Since 83bfff23e9ed ("nfs4: have do_vfs_lock take an inode pointer") has
> > removed the need to traverse fl->fl_file->f_inode in nfs4_lock_done(),
> > taking that reference is no longer necessary.
> [...]
> 
> No objection to this in 4.4, but that other commit only went into 4.2
> so this fix doesn't look suitable for 3.18.

Good catch, now dropped, thanks.

greg k-h