hfsplus: prevent crash on exit from failed search

hfs_find_exit() expects fd->bnode to be NULL after a search has failed.
hfs_brec_insert() may instead set it to an error-valued pointer.  Fix
this to prevent a crash.

Link: http://lkml.kernel.org/r/803590a35221fbf411b2c141419aea3233a6e990.1530294813.git.ernesto.mnd.fernandez@gmail.comSigned-off-by: Ernesto A. Fernandez <ernesto.mnd.fernandez@gmail.com>
Reported-by: Anatoly Trosinenko <anatoly.trosinenko@gmail.com>
Reviewed-by: Vyacheslav Dubeyko <slava@dubeyko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/hfsplus/brec.c

@@ -73,9 +73,10 @@ int hfs_brec_insert(struct hfs_find_data *fd, void *entry, int entry_len)
 	if (!fd->bnode) {
 		if (!tree->root)
 			hfs_btree_inc_height(tree);
-		fd->bnode = hfs_bnode_find(tree, tree->leaf_head);
-		if (IS_ERR(fd->bnode))
-			return PTR_ERR(fd->bnode);
+		node = hfs_bnode_find(tree, tree->leaf_head);
+		if (IS_ERR(node))
+			return PTR_ERR(node);
+		fd->bnode = node;
 		fd->record = -1;
 	}
 	new_node = NULL;