[ 3.8.y.z extended stable ] Patch "SUNRPC: Fix a deadlock in rpc_client_register()" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    SUNRPC: Fix a deadlock in rpc_client_register()

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.5.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 0c8af7ab642528003ddd8e2ae885d9a7794f9d85 Mon Sep 17 00:00:00 2001
From: Trond Myklebust <Trond.Myklebust at netapp.com>
Date: Wed, 10 Jul 2013 15:33:01 -0400
Subject: SUNRPC: Fix a deadlock in rpc_client_register()

commit eeee245268c951262b861bc1be4e9dc812352499 upstream.

Commit 384816051ca9125cd54750e59c780c2a2655fa4f (SUNRPC: fix races on
PipeFS MOUNT notifications) introduces a regression when we call
rpc_setup_pipedir() with RPCSEC_GSS as the auth flavour.

By calling rpcauth_create() while holding the sn->pipefs_sb_lock, we
end up deadlocking in gss_pipes_dentries_create_net().
Fix is to register the client and release the mutex before calling
rpcauth_create().

Reported-by: Weston Andros Adamson <dros at netapp.com>
Tested-by: Weston Andros Adamson <dros at netapp.com>
Cc: Stanislav Kinsbursky <skinsbursky at parallels.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust at netapp.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/sunrpc/clnt.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index d6e52e9..ce0913a 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -287,7 +287,7 @@ static int rpc_client_register(const struct rpc_create_args *args,
 	struct rpc_auth *auth;
 	struct net *net = rpc_net_ns(clnt);
 	struct super_block *pipefs_sb;
-	int err = 0;
+	int err;

 	pipefs_sb = rpc_get_sb_net(net);
 	if (pipefs_sb) {
@@ -296,6 +296,10 @@ static int rpc_client_register(const struct rpc_create_args *args,
 			goto out;
 	}

+	rpc_register_client(clnt);
+	if (pipefs_sb)
+		rpc_put_sb_net(net);
+
 	auth = rpcauth_create(args->authflavor, clnt);
 	if (IS_ERR(auth)) {
 		dprintk("RPC:       Couldn't create auth handle (flavor %u)\n",
@@ -303,16 +307,14 @@ static int rpc_client_register(const struct rpc_create_args *args,
 		err = PTR_ERR(auth);
 		goto err_auth;
 	}
-
-	rpc_register_client(clnt);
+	return 0;
+err_auth:
+	pipefs_sb = rpc_get_sb_net(net);
+	__rpc_clnt_remove_pipedir(clnt);
 out:
 	if (pipefs_sb)
 		rpc_put_sb_net(net);
 	return err;
-
-err_auth:
-	__rpc_clnt_remove_pipedir(clnt);
-	goto out;
 }

 static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, struct rpc_xprt *xprt)
--
1.8.1.2