linux-kernel - Re: [PATCH] clk: sunxi: Remove use of VLAIS

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Date:	Fri, 4 Mar 2016 09:18:41 -0800
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:	Chen-Yu Tsai <wens@...e.org>,
	Michael Turquette <mturquette@...libre.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-clk <linux-clk@...r.kernel.org>
Subject: Re: [PATCH] clk: sunxi: Remove use of VLAIS

On 03/04, Maxime Ripard wrote:
> On Thu, Mar 03, 2016 at 11:16:04AM -0800, Stephen Boyd wrote:
> > From: Stephen Boyd <sboyd@...eaurora.org>
> > Subject: [PATCH] clk: sunxi: Remove use of VLAIS
> 
> VLAIS?

Hmm I guess it's just VLA, so llvm won't break. I'll reword
commit text.

> 
> > @@ -107,6 +112,8 @@ err_free_div:
> >  	kfree(div);
> >  err_unmap:
> >  	iounmap(reg);
> > +err_free_parents:
> > +	kfree(parents);
> >  	of_address_to_resource(node, 0, &res);
> >  	release_mem_region(res.start, resource_size(&res));
> 
> The error path is wrong here, if you jump here from a failing call to
> of_io_request_and_map, you'll end up releasing a memory region which
> is not requested.
> 

Oh right. Let's hope third time is the last.

---8<---
From: Stephen Boyd <sboyd@...eaurora.org>
Subject: [PATCH] clk: sunxi: Remove use of variable length array

Using an array allocated on the stack may lead to stack overflows
and other problems so let's move the allocation to the heap
instead. This silences the following checker warning as well.

drivers/clk/sunxi/clk-sun8i-mbus.c:36:29: warning: Variable length array is used.

Cc: Chen-Yu Tsai <wens@...e.org>
Cc: Maxime Ripard <maxime.ripard@...e-electrons.com>
Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
---
 drivers/clk/sunxi/clk-sun8i-mbus.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/sunxi/clk-sun8i-mbus.c b/drivers/clk/sunxi/clk-sun8i-mbus.c
index 3aaa9cbef791..411d3033a96e 100644
--- a/drivers/clk/sunxi/clk-sun8i-mbus.c
+++ b/drivers/clk/sunxi/clk-sun8i-mbus.c
@@ -33,7 +33,7 @@ static DEFINE_SPINLOCK(sun8i_a23_mbus_lock);
 static void __init sun8i_a23_mbus_setup(struct device_node *node)
 {
 	int num_parents = of_clk_get_parent_count(node);
-	const char *parents[num_parents];
+	const char **parents;
 	const char *clk_name = node->name;
 	struct resource res;
 	struct clk_divider *div;
@@ -43,10 +43,14 @@ static void __init sun8i_a23_mbus_setup(struct device_node *node)
 	void __iomem *reg;
 	int err;
 
+	parents = kcalloc(num_parents, sizeof(*parents), GFP_KERNEL);
+	if (!parents)
+		return;
+
 	reg = of_io_request_and_map(node, 0, of_node_full_name(node));
 	if (!reg) {
 		pr_err("Could not get registers for sun8i-mbus-clk\n");
-		return;
+		goto err_free_parents;
 	}
 
 	div = kzalloc(sizeof(*div), GFP_KERNEL);
@@ -90,6 +94,7 @@ static void __init sun8i_a23_mbus_setup(struct device_node *node)
 	if (err)
 		goto err_unregister_clk;
 
+	kfree(parents); /* parents is deep copied */
 	/* The MBUS clocks needs to be always enabled */
 	__clk_get(clk);
 	clk_prepare_enable(clk);
@@ -109,5 +114,7 @@ err_unmap:
 	iounmap(reg);
 	of_address_to_resource(node, 0, &res);
 	release_mem_region(res.start, resource_size(&res));
+err_free_parents:
+	kfree(parents);
 }
 CLK_OF_DECLARE(sun8i_a23_mbus, "allwinner,sun8i-a23-mbus-clk", sun8i_a23_mbus_setup);
-- 
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