2 files changed, 34 insertions, 24 deletions

diff --git a/fs/lockd/clntproc.c b/fs/lockd/clntproc.c
index cebcc283b7ce..8728b53cf2e8 100644
--- a/fs/lockd/clntproc.c
+++ b/fs/lockd/clntproc.c
@@ -487,9 +487,12 @@ static const struct file_lock_operations nlmclnt_lock_ops = {
 static void nlmclnt_locks_init_private(struct file_lock *fl, struct nlm_host *host)
 {
 	fl->fl_u.nfs_fl.state = 0;
+	fl->fl_ops = NULL;
 	fl->fl_u.nfs_fl.owner = nlmclnt_find_lockowner(host,
 						       fl->c.flc_owner);
 	INIT_LIST_HEAD(&fl->fl_u.nfs_fl.list);
+	if (!fl->fl_u.nfs_fl.owner)
+		return;
 	fl->fl_ops = &nlmclnt_lock_ops;
 }
 
diff --git a/fs/lockd/svcsubs.c b/fs/lockd/svcsubs.c
index d11beea76ddb..91a4c22c86ff 100644
--- a/fs/lockd/svcsubs.c
+++ b/fs/lockd/svcsubs.c
@@ -301,12 +301,10 @@ nlm_file_inuse(struct nlm_file *file)
 	return 0;
 }
 
-static void nlm_close_files(struct nlm_file *file)
+static void nlm_file_release(struct nlm_file *file)
 {
-	if (file->f_file[O_RDONLY])
-		nlmsvc_ops->fclose(file->f_file[O_RDONLY]);
-	if (file->f_file[O_WRONLY])
-		nlmsvc_ops->fclose(file->f_file[O_WRONLY]);
+	if (!nlm_file_inuse(file))
+		nlm_delete_file(file);
 }
 
 /*
@@ -316,32 +314,41 @@ static int
 nlm_traverse_files(void *data, nlm_host_match_fn_t match,
 		int (*is_failover_file)(void *data, struct nlm_file *file))
 {
-	struct hlist_node *next;
-	struct nlm_file	*file;
+	struct nlm_file *file, *next;
 	int i, ret = 0;
 
 	mutex_lock(&nlm_file_mutex);
 	for (i = 0; i < FILE_NRHASH; i++) {
-		hlist_for_each_entry_safe(file, next, &nlm_files[i], f_list) {
-			if (is_failover_file && !is_failover_file(data, file))
-				continue;
+		file = hlist_entry_safe(nlm_files[i].first,
+					struct nlm_file, f_list);
+		if (file)
 			file->f_count++;
-			mutex_unlock(&nlm_file_mutex);
-
-			/* Traverse locks, blocks and shares of this file
-			 * and update file->f_locks count */
-			if (nlm_inspect_file(data, file, match))
-				ret = 1;
+		while (file) {
+			/*
+			 * Pin the next neighbour before we drop the mutex
+			 * for nlm_inspect_file(); a concurrent
+			 * nlm_release_file() under the same mutex would
+			 * otherwise be free to unlink and kfree it during
+			 * the unlock window, leaving us to dereference a
+			 * freed slab when we walked to next afterwards.
+			 */
+			next = hlist_entry_safe(file->f_list.next,
+						struct nlm_file, f_list);
+			if (next)
+				next->f_count++;
+
+			if (!is_failover_file || is_failover_file(data, file)) {
+				mutex_unlock(&nlm_file_mutex);
+
+				if (nlm_inspect_file(data, file, match))
+					ret = 1;
+
+				mutex_lock(&nlm_file_mutex);
+			}
 
-			mutex_lock(&nlm_file_mutex);
 			file->f_count--;
-			/* No more references to this file. Let go of it. */
-			if (list_empty(&file->f_blocks) && !file->f_locks
-			 && !file->f_shares && !file->f_count) {
-				hlist_del(&file->f_list);
-				nlm_close_files(file);
-				kfree(file);
-			}
+			nlm_file_release(file);
+			file = next;
 		}
 	}
 	mutex_unlock(&nlm_file_mutex);