clk: check for invalid parent index of orphans in __clk_init()

If a mux clock is initialised (by hardware or firmware) with an
invalid parent, its ->get_parent() can return an out of range
index.  For example, the generic mux clock attempts to return
-EINVAL, which due to the u8 return type ends up a rather large
number.  Using this index with the parent_names[] array results
in an invalid pointer and (usually) a crash in the following
strcmp().

This patch adds a check for the parent index being in range,
ignoring clocks reporting invalid values.
Signed-off-by: NMans Rullgard <mans@mansr.com>
Tested-by: NRhyland Klein <rklein@nvidia.com>
Signed-off-by: NStephen Boyd <sboyd@codeaurora.org>

drivers/clk/clk.c

@@ -2437,7 +2437,8 @@ static int __clk_init(struct device *dev, struct clk *clk_user)
 	hlist_for_each_entry_safe(orphan, tmp2, &clk_orphan_list, child_node) {
 		if (orphan->num_parents && orphan->ops->get_parent) {
 			i = orphan->ops->get_parent(orphan->hw);
-			if (!strcmp(core->name, orphan->parent_names[i]))
+			if (i >= 0 && i < orphan->num_parents &&
+			    !strcmp(core->name, orphan->parent_names[i]))
 				clk_core_reparent(orphan, core);
 			continue;
 		}