linux-kernel - [PATCH 3.16 157/357] NFSv4: nfs4_state_manager() vs. nfs_server_remove

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Date:	Fri,  3 Oct 2014 14:29:03 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Steve Dickson <steved@...hat.com>,
	Trond Myklebust <trond.myklebust@...marydata.com>
Subject: [PATCH 3.16 157/357] NFSv4: nfs4_state_manager() vs. nfs_server_remove_lists()

3.16-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: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/nfs/nfs4client.c |   38 ++++++++++++++++++++------------------
 1 file changed, 20 insertions(+), 18 deletions(-)

--- a/fs/nfs/nfs4client.c
+++ b/fs/nfs/nfs4client.c
@@ -482,6 +482,16 @@ int nfs40_walk_client_list(struct nfs_cl
 
 	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) {
@@ -501,15 +511,6 @@ int nfs40_walk_client_list(struct nfs_cl
 		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;
 
@@ -622,6 +623,16 @@ int nfs41_walk_client_list(struct nfs_cl
 
 	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
@@ -647,15 +658,6 @@ int nfs41_walk_client_list(struct nfs_cl
 		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;
 


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