Commit 5a7efdac authored Apr 12, 2019 by Stephen Boyd

clkdev: Hold clocks_mutex while iterating clocks list



We recently introduced a change to support devm clk lookups. That change
introduced a code-path that used clk_find() without holding the
'clocks_mutex'. Unfortunately, clk_find() iterates over the 'clocks'
list and so we need to prevent the list from being modified at the same
time. Do this by holding the mutex and checking to make sure it's held
while iterating the list.

Note, we don't really care if the lookup is freed after we find it with
clk_find() because we're just doing a pointer comparison, but if we did
care we would need to keep holding the mutex while we dereference the
clk_lookup pointer.

Fixes: 3eee6c7d ("clkdev: add managed clkdev lookup registration")
Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Jerome Brunet <jbrunet@baylibre.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Jeffrey Hugo <jhugo@codeaurora.org>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Acked-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Tested-by: Jeffrey Hugo <jhugo@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

parent f89b9e1b

drivers/clk/clkdev.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -46,6 +46,8 @@ static struct clk_lookup clk_find(const char dev_id, const char *con_id)
		if (con_id)
		best_possible += 1;

		lockdep_assert_held(&clocks_mutex);

		list_for_each_entry(p, &clocks, node) {
		match = 0;
		if (p->dev_id) {
		@@ -402,7 +404,10 @@ void devm_clk_release_clkdev(struct device dev, const char con_id,
		struct clk_lookup *cl;
		int rval;

		mutex_lock(&clocks_mutex);
		cl = clk_find(dev_id, con_id);
		mutex_unlock(&clocks_mutex);

		WARN_ON(!cl);
		rval = devres_release(dev, devm_clkdev_release,
		devm_clk_match_clkdev, cl);

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