linux-kernel - [PATCH 3.16 119/370] NFSv4.1: nfs4_fl_prepare_ds must be careful about reporting success.

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Message-ID: <lsq.1489146382.714000561@decadent.org.uk>
Date:   Fri, 10 Mar 2017 11:46:22 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Adamson, Andy" <William.Adamson@...app.com>,
        "Trond Myklebust" <trond.myklebust@...marydata.com>,
        "Olga Kornievskaia" <aglo@...ch.edu>, "NeilBrown" <neilb@...e.com>
Subject: [PATCH 3.16 119/370] NFSv4.1: nfs4_fl_prepare_ds must be careful
 about reporting success.

3.16.42-rc1 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: Ben Hutchings <ben@...adent.org.uk>
---
 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
@@ -827,7 +827,8 @@ nfs4_fl_prepare_ds(struct pnfs_layout_se
 		nfs4_wait_ds_connect(ds);
 	}
 out_test_devid:
-	if (filelayout_test_devid_unavailable(devid))
+	if (ret->ds_clp == NULL ||
+	    filelayout_test_devid_unavailable(devid))
 		ret = NULL;
 out:
 	return ret;