linux-kernel - [PATCH 3.13 102/163] NFSv4: nfs4_state_manager() vs. nfs_server_remove

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Message-Id: <1412888588-26755-103-git-send-email-kamal@canonical.com>
Date:	Thu,  9 Oct 2014 14:02:07 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Steve Dickson <steved@...hat.com>,
	Trond Myklebust <trond.myklebust@...marydata.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.13 102/163] NFSv4: nfs4_state_manager() vs. nfs_server_remove_lists()

3.13.11.9 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Steve Dickson <steved@...hat.com>

commit 080af20cc945d110f9912d01cf6b66f94a375b8d upstream.

There is a race between nfs4_state_manager() and
nfs_server_remove_lists() that happens during a nfsv3 mount.

The v3 mount notices there is already a supper block so
nfs_server_remove_lists() called which uses the nfs_client_lock
spin lock to synchronize access to the client list.

At the same time nfs4_state_manager() is running through
the client list looking for work to do, using the same
lock. When nfs4_state_manager() wins the race to the
list, a v3 client pointer is found and not ignored
properly which causes the panic.

Moving some protocol checks before the state checking
avoids the panic.

Signed-off-by: Steve Dickson <steved@...hat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@...marydata.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 fs/nfs/nfs4client.c | 38 ++++++++++++++++++++------------------
 1 file changed, 20 insertions(+), 18 deletions(-)

diff --git a/fs/nfs/nfs4client.c b/fs/nfs/nfs4client.c
index 4c7bd2c..af6013c 100644
--- a/fs/nfs/nfs4client.c
+++ b/fs/nfs/nfs4client.c
@@ -485,6 +485,16 @@ int nfs40_walk_client_list(struct nfs_client *new,
 
 	spin_lock(&nn->nfs_client_lock);
 	list_for_each_entry(pos, &nn->nfs_client_list, cl_share_link) {
+
+		if (pos->rpc_ops != new->rpc_ops)
+			continue;
+
+		if (pos->cl_proto != new->cl_proto)
+			continue;
+
+		if (pos->cl_minorversion != new->cl_minorversion)
+			continue;
+
 		/* If "pos" isn't marked ready, we can't trust the
 		 * remaining fields in "pos" */
 		if (pos->cl_cons_state > NFS_CS_READY) {
@@ -504,15 +514,6 @@ int nfs40_walk_client_list(struct nfs_client *new,
 		if (pos->cl_cons_state != NFS_CS_READY)
 			continue;
 
-		if (pos->rpc_ops != new->rpc_ops)
-			continue;
-
-		if (pos->cl_proto != new->cl_proto)
-			continue;
-
-		if (pos->cl_minorversion != new->cl_minorversion)
-			continue;
-
 		if (pos->cl_clientid != new->cl_clientid)
 			continue;
 
@@ -618,6 +619,16 @@ int nfs41_walk_client_list(struct nfs_client *new,
 
 	spin_lock(&nn->nfs_client_lock);
 	list_for_each_entry(pos, &nn->nfs_client_list, cl_share_link) {
+
+		if (pos->rpc_ops != new->rpc_ops)
+			continue;
+
+		if (pos->cl_proto != new->cl_proto)
+			continue;
+
+		if (pos->cl_minorversion != new->cl_minorversion)
+			continue;
+
 		/* If "pos" isn't marked ready, we can't trust the
 		 * remaining fields in "pos", especially the client
 		 * ID and serverowner fields.  Wait for CREATE_SESSION
@@ -643,15 +654,6 @@ int nfs41_walk_client_list(struct nfs_client *new,
 		if (pos->cl_cons_state != NFS_CS_READY)
 			continue;
 
-		if (pos->rpc_ops != new->rpc_ops)
-			continue;
-
-		if (pos->cl_proto != new->cl_proto)
-			continue;
-
-		if (pos->cl_minorversion != new->cl_minorversion)
-			continue;
-
 		if (!nfs4_match_clientids(pos, new))
 			continue;
 
-- 
1.9.1

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