With the split into struct clk and struct clk_core, clocks lost the ability for nested __clk_get clkdev calls. While it stays possible to call __clk_get, the first call to (__)clk_put will clear the struct clk, making subsequent clk_put calls run into a NULL pointer dereference.
One prime example of this sits in the generic power domain code, where it is possible to add the clocks both by name and by passing in a struct clk via pm_clk_add_clk(). __pm_clk_add() in turn then calls __clk_get to increase the refcount, so that the original code can put the clock again. A possible call-path looks like clk = of_clk_get(); pm_clk_add_clk(dev, clk); clk_put(clk); with pm_clk_add_clk() => __pm_clk_add() then calling __clk_get on the clk and later clk_put when the pm clock list gets destroyed, thus creating a NULL pointer deref, as the struct clk doesn't exist anymore. So add a separate refcounting for struct clk instances and only clean up once the refcount reaches zero. Signed-off-by: Heiko Stuebner <[email protected]> --- I stumbled upon this while applying the new Rockchip power-domain driver, but I guess the underlying issue is universal and probably present since the original clk/clk_core split, so this probably counts as fix. drivers/clk/clk.c | 31 +++++++++++++++++++++---------- 1 file changed, 21 insertions(+), 10 deletions(-) diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index 43e2c3a..7aab1a4 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -85,6 +85,7 @@ struct clk { unsigned long min_rate; unsigned long max_rate; struct hlist_node clks_node; + struct kref ref; }; /*** locking ***/ @@ -2590,7 +2591,7 @@ fail_out: EXPORT_SYMBOL_GPL(clk_register); /* Free memory allocated for a clock. */ -static void __clk_release(struct kref *ref) +static void __clk_core_release(struct kref *ref) { struct clk_core *core = container_of(ref, struct clk_core, ref); int i = core->num_parents; @@ -2606,6 +2607,18 @@ static void __clk_release(struct kref *ref) kfree(core); } +static void __clk_release(struct kref *ref) +{ + struct clk *clk = container_of(ref, struct clk, ref); + + hlist_del(&clk->clks_node); + if ((clk->min_rate > clk->core->req_rate || + clk->max_rate < clk->core->req_rate)) + clk_core_set_rate_nolock(clk->core, clk->core->req_rate); + + kfree(clk); +} + /* * Empty clk_ops for unregistered clocks. These are used temporarily * after clk_unregister() was called on a clock and until last clock @@ -2684,7 +2697,7 @@ void clk_unregister(struct clk *clk) if (clk->core->prepare_count) pr_warn("%s: unregistering prepared clock: %s\n", __func__, clk->core->name); - kref_put(&clk->core->ref, __clk_release); + kref_put(&clk->core->ref, __clk_core_release); clk_prepare_unlock(); } @@ -2759,12 +2772,14 @@ int __clk_get(struct clk *clk) return 0; kref_get(&core->ref); + kref_get(&clk->ref); } return 1; } void __clk_put(struct clk *clk) { + struct clk_core *core; struct module *owner; if (!clk || WARN_ON_ONCE(IS_ERR(clk))) @@ -2772,19 +2787,15 @@ void __clk_put(struct clk *clk) clk_prepare_lock(); - hlist_del(&clk->clks_node); - if (clk->min_rate > clk->core->req_rate || - clk->max_rate < clk->core->req_rate) - clk_core_set_rate_nolock(clk->core, clk->core->req_rate); + core = clk->core; + owner = core->owner; - owner = clk->core->owner; - kref_put(&clk->core->ref, __clk_release); + kref_put(&clk->ref, __clk_release); + kref_put(&core->ref, __clk_core_release); clk_prepare_unlock(); module_put(owner); - - kfree(clk); } /*** clk rate change notifiers ***/ -- 2.5.1 -- To unsubscribe from this list: send the line "unsubscribe linux-clk" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
