linux-kernel - [PATCH 4.4 40/48] NFSv4.1: nfs4_fl_prepare_ds must be careful about reporting success.

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Date:   Wed, 18 Jan 2017 11:46:49 +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, NeilBrown <neilb@...e.com>,
        Olga Kornievskaia <aglo@...ch.edu>,
        "Adamson, Andy" <William.Adamson@...app.com>,
        Trond Myklebust <trond.myklebust@...marydata.com>
Subject: [PATCH 4.4 40/48] NFSv4.1: nfs4_fl_prepare_ds must be careful about reporting success.

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: NeilBrown <neilb@...e.com>

commit cfd278c280f997cf2fe4662e0acab0fe465f637b upstream.

Various places assume that if nfs4_fl_prepare_ds() turns a non-NULL 'ds',
then ds->ds_clp will also be non-NULL.

This is not necessasrily true in the case when the process received a fatal signal
while nfs4_pnfs_ds_connect is waiting in nfs4_wait_ds_connect().
In that case ->ds_clp may not be set, and the devid may not recently have been marked
unavailable.

So add a test for ds_clp == NULL and return NULL in that case.

Fixes: c23266d532b4 ("NFS4.1 Fix data server connection race")
Signed-off-by: NeilBrown <neilb@...e.com>
Acked-by: Olga Kornievskaia <aglo@...ch.edu>
Acked-by: Adamson, Andy <William.Adamson@...app.com>
Signed-off-by: Trond Myklebust <trond.myklebust@...marydata.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/nfs/filelayout/filelayoutdev.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/nfs/filelayout/filelayoutdev.c
+++ b/fs/nfs/filelayout/filelayoutdev.c
@@ -283,7 +283,8 @@ nfs4_fl_prepare_ds(struct pnfs_layout_se
 			     s->nfs_client->cl_rpcclient->cl_auth->au_flavor);
 
 out_test_devid:
-	if (filelayout_test_devid_unavailable(devid))
+	if (ret->ds_clp == NULL ||
+	    filelayout_test_devid_unavailable(devid))
 		ret = NULL;
 out:
 	return ret;