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clkdev: Fix race condition in clock lookup from device tree

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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>
This commit is contained in:
Sylwester Nawrocki 2013-08-23 17:03:44 +02:00
parent d6782c2636
commit 3a3d2b0551
1 changed files with 10 additions and 2 deletions
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12
drivers/clk/clkdev.c
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@ -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;
}