[PATCH] NLM: Don't hang forever on NLM unlock requests - CVE-2011-2491

[Paolo Pisati]

From: Trond Myklebust <Trond.Myklebust at netapp.com>

NLM: Don't hang forever on NLM unlock requests

If the NLM daemon is killed on the NFS server, we can currently end up
hanging forever on an 'unlock' request, instead of aborting. Basically,
if the rpcbind request fails, or the server keeps returning garbage, we
really want to quit instead of retrying.

Tested-by: Vasily Averin <vvs at sw.ru>
Signed-off-by: Trond Myklebust <Trond.Myklebust at netapp.com>
Cc: stable at kernel.org

CVE-2011-2491

BugLink: http://bugs.launchpad.net/bugs/869237

(cherry picked from commit 0b760113a3a155269a3fba93a409c640031dd68f)

Signed-off-by: Paolo Pisati <paolo.pisati at canonical.com>
---
 fs/lockd/clntproc.c          |    8 +++++++-
 include/linux/sunrpc/sched.h |    3 ++-
 net/sunrpc/clnt.c            |    3 +++
 net/sunrpc/sched.c           |    1 +
 4 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/fs/lockd/clntproc.c b/fs/lockd/clntproc.c
index adb45ec..e374050 100644
--- a/fs/lockd/clntproc.c
+++ b/fs/lockd/clntproc.c
@@ -708,7 +708,13 @@ static void nlmclnt_unlock_callback(struct rpc_task *task, void *data)
 
 	if (task->tk_status < 0) {
 		dprintk("lockd: unlock failed (err = %d)\n", -task->tk_status);
-		goto retry_rebind;
+		switch (task->tk_status) {
+		case -EACCES:
+		case -EIO:
+			goto die;
+		default:
+			goto retry_rebind;
+		}
 	}
 	if (status == NLM_LCK_DENIED_GRACE_PERIOD) {
 		rpc_delay(task, NLMCLNT_GRACE_WAIT);
diff --git a/include/linux/sunrpc/sched.h b/include/linux/sunrpc/sched.h
index d81db80..86993a3 100644
--- a/include/linux/sunrpc/sched.h
+++ b/include/linux/sunrpc/sched.h
@@ -84,7 +84,8 @@ struct rpc_task {
 #endif
 	unsigned char		tk_priority : 2,/* Task priority */
 				tk_garb_retry : 2,
-				tk_cred_retry : 2;
+				tk_cred_retry : 2,
+				tk_rebind_retry : 2;
 };
 #define tk_xprt			tk_client->cl_xprt
 
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 35d046b..fe52109 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -1170,6 +1170,9 @@ call_bind_status(struct rpc_task *task)
 			status = -EOPNOTSUPP;
 			break;
 		}
+		if (task->tk_rebind_retry == 0)
+			break;
+		task->tk_rebind_retry--;
 		rpc_delay(task, 3*HZ);
 		goto retry_timeout;
 	case -ETIMEDOUT:
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index 17c3e3a..11d8642 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -799,6 +799,7 @@ static void rpc_init_task(struct rpc_task *task, const struct rpc_task_setup *ta
 	/* Initialize retry counters */
 	task->tk_garb_retry = 2;
 	task->tk_cred_retry = 2;
+	task->tk_rebind_retry = 2;
 
 	task->tk_priority = task_setup_data->priority - RPC_PRIORITY_LOW;
 	task->tk_owner = current->tgid;
-- 
1.7.5.4