linux-kernel - [PATCH] clk: check for invalid parent index of orphans in __clk

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Message-Id: <1424003629-11383-1-git-send-email-mans@mansr.com>
Date:	Sun, 15 Feb 2015 12:33:49 +0000
From:	Mans Rullgard <mans@...sr.com>
To:	Mike Turquette <mturquette@...aro.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	linux-kernel@...r.kernel.org
Cc:	Rhyland Klein <rklein@...dia.com>
Subject: [PATCH] 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: Mans Rullgard <mans@...sr.com>
Cc: Rhyland Klein <rklein@...dia.com>
---
 drivers/clk/clk.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index d48ac71..bc0662b 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1950,7 +1950,8 @@ int __clk_init(struct device *dev, struct clk *clk)
 	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(clk->name, orphan->parent_names[i]))
+			if (i >= 0 && i < orphan->num_parents &&
+			    !strcmp(clk->name, orphan->parent_names[i]))
 				__clk_reparent(orphan, clk);
 			continue;
 		}
-- 
2.3.0

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