nfs4: fix discover_server_trunking use after free

If clp is new (cl_count = 1) and it matches another client in
nfs4_discover_server_trunking, the nfs_put_client will free clp before
->cl_preserve_clid is set.

Cc: stable@vger.kernel.org # 3.7+
Signed-off-by: Weston Andros Adamson <dros@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

1 files changed, 4 insertions, 6 deletions

diff --git a/fs/nfs/nfs4client.c b/fs/nfs/nfs4client.c
index 06e770ace073..73d4ecda1e36 100644
--- a/fs/nfs/nfs4client.c
+++ b/fs/nfs/nfs4client.c
@@ -414,13 +414,11 @@ struct nfs_client *nfs4_init_client(struct nfs_client *clp,
         error = nfs4_discover_server_trunking(clp, &old);
         if (error < 0)
                 goto error;
-        nfs_put_client(clp);
-        if (clp != old) {
-                clp->cl_preserve_clid = true;
-                clp = old;
-        }
 
-        return clp;
+        if (clp != old)
+                clp->cl_preserve_clid = true;
+        nfs_put_client(clp);
+        return old;
 
 error:
         nfs_mark_client_ready(clp, error);