SUNRPC: NULL utsname dereference on NFS umount during namespace cleanup

Fix an Oopsable condition when nsm_mon_unmon is called as part of the
namespace cleanup, which now apparently happens after the utsname
has been freed.

Link: http://lkml.kernel.org/r/20150125220604.090121ae@neptune.home
Reported-by: Bruno Prémont <bonbons@linux-vserver.org>
Cc: stable@vger.kernel.org # 3.18
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

1 files changed, 9 insertions, 4 deletions

diff --git a/fs/lockd/mon.c b/fs/lockd/mon.c
index 1cc6ec51e6b1..47a32b6d9b90 100644
--- a/fs/lockd/mon.c
+++ b/fs/lockd/mon.c
@@ -65,7 +65,7 @@ static inline struct sockaddr *nsm_addr(const struct nsm_handle *nsm)
         return (struct sockaddr *)&nsm->sm_addr;
 }
 
-static struct rpc_clnt *nsm_create(struct net *net)
+static struct rpc_clnt *nsm_create(struct net *net, const char *nodename)
 {
         struct sockaddr_in sin = {
                 .sin_family             = AF_INET,
@@ -77,6 +77,7 @@ static struct rpc_clnt *nsm_create(struct net *net)
                 .address                = (struct sockaddr *)&sin,
                 .addrsize               = sizeof(sin),
                 .servername             = "rpc.statd",
+                .nodename               = nodename,
                 .program                = &nsm_program,
                 .version                = NSM_VERSION,
                 .authflavor             = RPC_AUTH_NULL,
@@ -102,7 +103,7 @@ out:
         return clnt;
 }
 
-static struct rpc_clnt *nsm_client_get(struct net *net)
+static struct rpc_clnt *nsm_client_get(struct net *net, const char *nodename)
 {
         struct rpc_clnt *clnt, *new;
         struct lockd_net *ln = net_generic(net, lockd_net_id);
@@ -111,7 +112,7 @@ static struct rpc_clnt *nsm_client_get(struct net *net)
         if (clnt != NULL)
                 goto out;
 
-        clnt = new = nsm_create(net);
+        clnt = new = nsm_create(net, nodename);
         if (IS_ERR(clnt))
                 goto out;
 
@@ -190,19 +191,23 @@ int nsm_monitor(const struct nlm_host *host)
         struct nsm_res  res;
         int             status;
         struct rpc_clnt *clnt;
+        const char *nodename = NULL;
 
         dprintk("lockd: nsm_monitor(%s)\n", nsm->sm_name);
 
         if (nsm->sm_monitored)
                 return 0;
 
+        if (host->h_rpcclnt)
+                nodename = host->h_rpcclnt->cl_nodename;
+
         /*
          * Choose whether to record the caller_name or IP address of
          * this peer in the local rpc.statd's database.
          */
         nsm->sm_mon_name = nsm_use_hostnames ? nsm->sm_name : nsm->sm_addrbuf;
 
-        clnt = nsm_client_get(host->net);
+        clnt = nsm_client_get(host->net, nodename);
         if (IS_ERR(clnt)) {
                 status = PTR_ERR(clnt);
                 dprintk("lockd: failed to create NSM upcall transport, "