Commit 3a3d2b05 authored Aug 23, 2013 by Sylwester Nawrocki

clkdev: Fix race condition in clock lookup from device tree



There is currently a race condition in the device tree part of clk_get()
function, since the pointer returned from of_clk_get_by_name() may become
invalid before __clk_get() call. E.g. due to the clock provider driver
remove() callback being called in between of_clk_get_by_name() and
__clk_get().

Fix this by doing both the look up and __clk_get() operations with the
clock providers list mutex held. This ensures that the clock pointer
returned from __of_clk_get_from_provider() call and passed to __clk_get()
is valid, as long as the clock supplier module first removes its clock
provider instance and then does clk_unregister() on the corresponding
clocks.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Mike Turquette <mturquette@linaro.org>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>

parent d6782c26

drivers/clk/clkdev.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -21,6 +21,8 @@
		#include <linux/clkdev.h>
		#include <linux/of.h>

		#include "clk.h"

		static LIST_HEAD(clocks);
		static DEFINE_MUTEX(clocks_mutex);

		@@ -39,7 +41,13 @@ struct clk of_clk_get(struct device_node np, int index)
		if (rc)
		return ERR_PTR(rc);

		clk = of_clk_get_from_provider(&clkspec);
		of_clk_lock();
		clk = __of_clk_get_from_provider(&clkspec);

		if (!IS_ERR(clk) && !__clk_get(clk))
		clk = ERR_PTR(-ENOENT);

		of_clk_unlock();
		of_node_put(clkspec.np);
		return clk;
		}
		@@ -157,7 +165,7 @@ struct clk clk_get(struct device dev, const char *con_id)

		if (dev) {
		clk = of_clk_get_by_name(dev->of_node, con_id);
		if (!IS_ERR(clk) && __clk_get(clk))
		if (!IS_ERR(clk))
		return clk;
		}