clkdev: use clk_hw internally

clk_add_alias() calls clk_get() followed by clk_put() but in between
those two calls it saves away the struct clk pointer to a clk_lookup
structure. This leaves the 'clk' member of the clk_lookup pointing at
freed memory on configurations where CONFIG_COMMON_CLK=y. This is a
problem because clk_get_sys() will eventually try to dereference the
freed pointer by calling __clk_get_hw() on it. Fix this by saving away
the struct clk_hw pointer instead of the struct clk pointer so that when
we try to create a per-user struct clk in clk_get_sys() we don't
dereference a junk pointer.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

drivers/clk/clkdev.c

@@ -177,7 +177,7 @@ struct clk *clk_get_sys(const char *dev_id, const char *con_id)
 	if (!cl)
 		goto out;
 
-	clk = __clk_create_clk(__clk_get_hw(cl->clk), dev_id, con_id);
+	clk = __clk_create_clk(cl->clk_hw, dev_id, con_id);
 	if (IS_ERR(clk))
 		goto out;
 
@@ -215,18 +215,26 @@ void clk_put(struct clk *clk)
 }
 EXPORT_SYMBOL(clk_put);
 
-void clkdev_add(struct clk_lookup *cl)
+static void __clkdev_add(struct clk_lookup *cl)
 {
 	mutex_lock(&clocks_mutex);
 	list_add_tail(&cl->node, &clocks);
 	mutex_unlock(&clocks_mutex);
 }
+
+void clkdev_add(struct clk_lookup *cl)
+{
+	if (!cl->clk_hw)
+		cl->clk_hw = __clk_get_hw(cl->clk);
+	__clkdev_add(cl);
+}
 EXPORT_SYMBOL(clkdev_add);
 
 void __init clkdev_add_table(struct clk_lookup *cl, size_t num)
 {
 	mutex_lock(&clocks_mutex);
 	while (num--) {
+		cl->clk_hw = __clk_get_hw(cl->clk);
 		list_add_tail(&cl->node, &clocks);
 		cl++;
 	}
@@ -243,7 +251,7 @@ struct clk_lookup_alloc {
 };
 
 static struct clk_lookup * __init_refok
-vclkdev_alloc(struct clk *clk, const char *con_id, const char *dev_fmt,
+vclkdev_alloc(struct clk_hw *hw, const char *con_id, const char *dev_fmt,
 	va_list ap)
 {
 	struct clk_lookup_alloc *cla;
@@ -252,7 +260,7 @@ vclkdev_alloc(struct clk *clk, const char *con_id, const char *dev_fmt,
 	if (!cla)
 		return NULL;
 
-	cla->cl.clk = clk;
+	cla->cl.clk_hw = hw;
 	if (con_id) {
 		strlcpy(cla->con_id, con_id, sizeof(cla->con_id));
 		cla->cl.con_id = cla->con_id;
@@ -273,7 +281,7 @@ clkdev_alloc(struct clk *clk, const char *con_id, const char *dev_fmt, ...)
 	va_list ap;
 
 	va_start(ap, dev_fmt);
-	cl = vclkdev_alloc(clk, con_id, dev_fmt, ap);
+	cl = vclkdev_alloc(__clk_get_hw(clk), con_id, dev_fmt, ap);
 	va_end(ap);
 
 	return cl;
@@ -334,7 +342,7 @@ int clk_register_clkdev(struct clk *clk, const char *con_id,
 		return PTR_ERR(clk);
 
 	va_start(ap, dev_fmt);
-	cl = vclkdev_alloc(clk, con_id, dev_fmt, ap);
+	cl = vclkdev_alloc(__clk_get_hw(clk), con_id, dev_fmt, ap);
 	va_end(ap);
 
 	if (!cl)
@@ -365,8 +373,8 @@ int clk_register_clkdevs(struct clk *clk, struct clk_lookup *cl, size_t num)
 		return PTR_ERR(clk);
 
 	for (i = 0; i < num; i++, cl++) {
-		cl->clk = clk;
-		clkdev_add(cl);
+		cl->clk_hw = __clk_get_hw(clk);
+		__clkdev_add(cl);
 	}
 
 	return 0;

include/linux/clkdev.h

@@ -22,6 +22,7 @@ struct clk_lookup {
 	const char		*dev_id;
 	const char		*con_id;
 	struct clk		*clk;
+	struct clk_hw		*clk_hw;
 };
 
 #define CLKDEV_INIT(d, n, c)	\