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Subject[ 093/187] clk: fix parent validation in __clk_set_parent()
Date
From: Greg KH <gregkh@linuxfoundation.org>

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

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

From: Rajendra Nayak <rnayak@ti.com>

commit 863b13271f1608ab3af6f7a371047d9a66693e38 upstream.

The below commit introduced a bug in __clk_set_parent()
which could cause it to *skip* the parent validation
which makes sure the parent passed to the api is a valid
one.

commit 7975059db572eb47f0fb272a62afeae272a4b209
Author: Rajendra Nayak <rnayak@ti.com>
Date: Wed Jun 6 14:41:31 2012 +0530

clk: Allow late cache allocation for clk->parents

This was identified by the following compiler warning..

drivers/clk/clk.c: In function '__clk_set_parent':
drivers/clk/clk.c:1083:5: warning: 'i' may be used uninitialized in this function [-Wuninitialized]

.. as reported by Marc Kleine-Budde.

There were various options discussed on how to fix this, one
being initing 'i' to clk->num_parents, but the below approach
was found to be more appropriate as it also makes the 'parent
validation' code simpler to read.

Reported-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/clk/clk.c | 28 +++++++++++++---------------
1 file changed, 13 insertions(+), 15 deletions(-)

--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1062,26 +1062,24 @@ static int __clk_set_parent(struct clk *

old_parent = clk->parent;

- /* find index of new parent clock using cached parent ptrs */
- if (clk->parents)
- for (i = 0; i < clk->num_parents; i++)
- if (clk->parents[i] == parent)
- break;
- else
+ if (!clk->parents)
clk->parents = kzalloc((sizeof(struct clk*) * clk->num_parents),
GFP_KERNEL);

/*
- * find index of new parent clock using string name comparison
- * also try to cache the parent to avoid future calls to __clk_lookup
+ * find index of new parent clock using cached parent ptrs,
+ * or if not yet cached, use string name comparison and cache
+ * them now to avoid future calls to __clk_lookup.
*/
- if (i == clk->num_parents)
- for (i = 0; i < clk->num_parents; i++)
- if (!strcmp(clk->parent_names[i], parent->name)) {
- if (clk->parents)
- clk->parents[i] = __clk_lookup(parent->name);
- break;
- }
+ for (i = 0; i < clk->num_parents; i++) {
+ if (clk->parents && clk->parents[i] == parent)
+ break;
+ else if (!strcmp(clk->parent_names[i], parent->name)) {
+ if (clk->parents)
+ clk->parents[i] = __clk_lookup(parent->name);
+ break;
+ }
+ }

if (i == clk->num_parents) {
pr_debug("%s: clock %s is not a possible parent of clock %s\n",



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