clk: Check parent for NULL in clk_change_rate

clk_change_rate() is accessing parent's rate without checking
if the parent exists at all. In case of root clocks this will
cause NULL pointer dereference.

This patch follows what clk_calc_new_rates() does in such
situation.

Signed-off-by: Pawel Moll <pawel.moll@arm.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>
Cc: stable@kernel.org

1 files changed, 7 insertions, 4 deletions

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index df89cbfc1bd0..dcbe05616090 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -850,18 +850,21 @@ static void clk_change_rate(struct clk *clk)
 {
         struct clk *child;
         unsigned long old_rate;
+        unsigned long best_parent_rate = 0;
         struct hlist_node *tmp;
 
         old_rate = clk->rate;
 
+        if (clk->parent)
+                best_parent_rate = clk->parent->rate;
+
         if (clk->ops->set_rate)
-                clk->ops->set_rate(clk->hw, clk->new_rate, clk->parent->rate);
+                clk->ops->set_rate(clk->hw, clk->new_rate, best_parent_rate);
 
         if (clk->ops->recalc_rate)
-                clk->rate = clk->ops->recalc_rate(clk->hw,
-                                clk->parent->rate);
+                clk->rate = clk->ops->recalc_rate(clk->hw, best_parent_rate);
         else
-                clk->rate = clk->parent->rate;
+                clk->rate = best_parent_rate;
 
         if (clk->notifier_count && old_rate != clk->rate)
                 __clk_notify(clk, POST_RATE_CHANGE, old_rate, clk->rate);