Patchwork [106/222] NFS: avoid NULL dereference in nfs_destroy_server

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Submitter Herton Ronaldo Krzesinski
Date Jan. 16, 2013, 3:55 p.m.
Message ID <>
Download mbox | patch
Permalink /patch/212684/
State New
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Herton Ronaldo Krzesinski - Jan. 16, 2013, 3:55 p.m. -stable review patch.  If anyone has any objections, please let me know.


From: NeilBrown <>

commit f259613a1e4b44a0cf85a5dafd931be96ee7c9e5 upstream.

In rare circumstances, nfs_clone_server() of a v2 or v3 server can get
an error between setting server->destory (to nfs_destroy_server), and
calling nfs_start_lockd (which will set server->nlm_host).

If this happens, nfs_clone_server will call nfs_free_server which
will call nfs_destroy_server and thence nlmclnt_done(NULL).  This
causes the NULL to be dereferenced.

So add a guard to only call nlmclnt_done() if ->nlm_host is not NULL.

The other guards there are irrelevant as nlm_host can only be non-NULL
if one of these flags are set - so remove those tests.  (Thanks to Trond
for this suggestion).

This is suitable for any stable kernel since 2.6.25.

Signed-off-by: NeilBrown <>
Signed-off-by: Trond Myklebust <>
Signed-off-by: Herton Ronaldo Krzesinski <>
 fs/nfs/client.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)


diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index f005b5b..ede78be 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -689,8 +689,7 @@  static int nfs_create_rpc_client(struct nfs_client *clp,
 static void nfs_destroy_server(struct nfs_server *server)
-	if (!(server->flags & NFS_MOUNT_LOCAL_FLOCK) ||
-			!(server->flags & NFS_MOUNT_LOCAL_FCNTL))
+	if (server->nlm_host)