linux-kernel - [ 28/37] clk: Check parent for NULL in clk_change

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Message-Id: <20120717232433.716856099@linuxfoundation.org>
Date:	Tue, 17 Jul 2012 17:03:05 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Pawel Moll <pawel.moll@....com>,
	Mike Turquette <mturquette@...aro.org>
Subject: [ 28/37] clk: Check parent for NULL in clk_change_rate

From: Greg KH <gregkh@...uxfoundation.org>

3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Pawel Moll <pawel.moll@....com>

commit bf47b4fd8f9f81cd5ce40e1945c6334d088226d1 upstream.

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@....com>
Signed-off-by: Mike Turquette <mturquette@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/clk/clk.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -834,18 +834,21 @@ static void clk_change_rate(struct 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);
 
 	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);


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