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

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Date:   Thu,  7 Dec 2017 14:07:23 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.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: [PATCH 4.4 29/49] nfs: Dont take a reference on fl->fl_file for LOCK operation

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.

Signed-off-by: Benjamin Coddington <bcodding@...hat.com>
Reviewed-by: Jeff Layton <jlayton@...hat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@...marydata.com>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/nfs/nfs4proc.c |    3 ---
 1 file changed, 3 deletions(-)

--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -38,7 +38,6 @@
 #include <linux/mm.h>
 #include <linux/delay.h>
 #include <linux/errno.h>
-#include <linux/file.h>
 #include <linux/string.h>
 #include <linux/ratelimit.h>
 #include <linux/printk.h>
@@ -5738,7 +5737,6 @@ static struct nfs4_lockdata *nfs4_alloc_
 	p->server = server;
 	atomic_inc(&lsp->ls_count);
 	p->ctx = get_nfs_open_context(ctx);
-	get_file(fl->fl_file);
 	memcpy(&p->fl, fl, sizeof(p->fl));
 	return p;
 out_free_seqid:
@@ -5851,7 +5849,6 @@ static void nfs4_lock_release(void *call
 		nfs_free_seqid(data->arg.lock_seqid);
 	nfs4_put_lock_state(data->lsp);
 	put_nfs_open_context(data->ctx);
-	fput(data->fl.fl_file);
 	kfree(data);
 	dprintk("%s: done!\n", __func__);
 }