linux-kernel - [PATCH] opp: Don't drop reference for an OPP table that was never parsed

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Message-Id: <922ff0759a16299e24cacfc981ac07914d8f1826.1598865786.git.viresh.kumar@linaro.org>
Date:   Mon, 31 Aug 2020 14:56:56 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>
Cc:     Viresh Kumar <viresh.kumar@...aro.org>, linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Rafael Wysocki <rjw@...ysocki.net>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Douglas Anderson <dianders@...omium.org>,
        Naresh Kamboju <naresh.kamboju@...aro.org>,
        Anders Roxell <anders.roxell@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] opp: Don't drop reference for an OPP table that was never parsed

dev_pm_opp_remove_table() should drop a reference to the OPP table only
if the DT OPP table was parsed earlier with a call to
dev_pm_opp_of_add_table() earlier. Else it may end up dropping the
reference to the OPP table, which was added as a result of other calls
like dev_pm_opp_set_clkname(). And would hence result in undesirable
behavior later on when caller would try to free the resource again.

Fixes: 03758d60265c ("opp: Replace list_kref with a local counter")
Reported-by: Naresh Kamboju <naresh.kamboju@...aro.org>
Reported-by: Anders Roxell <anders.roxell@...aro.org>
Tested-by: Naresh Kamboju <naresh.kamboju@...aro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 drivers/opp/core.c | 22 ++++++++++++++++------
 drivers/opp/opp.h  |  2 +-
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index 9d7fb45b1786..31ce5d19ee9e 100644
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -1291,13 +1291,19 @@ void dev_pm_opp_remove(struct device *dev, unsigned long freq)
 }
 EXPORT_SYMBOL_GPL(dev_pm_opp_remove);
 
-void _opp_remove_all_static(struct opp_table *opp_table)
+bool _opp_remove_all_static(struct opp_table *opp_table)
 {
 	struct dev_pm_opp *opp, *tmp;
+	bool ret = true;
 
 	mutex_lock(&opp_table->lock);
 
-	if (!opp_table->parsed_static_opps || --opp_table->parsed_static_opps)
+	if (!opp_table->parsed_static_opps) {
+		ret = false;
+		goto unlock;
+	}
+
+	if (--opp_table->parsed_static_opps)
 		goto unlock;
 
 	list_for_each_entry_safe(opp, tmp, &opp_table->opp_list, node) {
@@ -1307,6 +1313,8 @@ void _opp_remove_all_static(struct opp_table *opp_table)
 
 unlock:
 	mutex_unlock(&opp_table->lock);
+
+	return ret;
 }
 
 /**
@@ -2409,13 +2417,15 @@ void _dev_pm_opp_find_and_remove_table(struct device *dev)
 		return;
 	}
 
-	_opp_remove_all_static(opp_table);
+	/*
+	 * Drop the extra reference only if the OPP table was successfully added
+	 * with dev_pm_opp_of_add_table() earlier.
+	 **/
+	if (_opp_remove_all_static(opp_table))
+		dev_pm_opp_put_opp_table(opp_table);
 
 	/* Drop reference taken by _find_opp_table() */
 	dev_pm_opp_put_opp_table(opp_table);
-
-	/* Drop reference taken while the OPP table was added */
-	dev_pm_opp_put_opp_table(opp_table);
 }
 
 /**
diff --git a/drivers/opp/opp.h b/drivers/opp/opp.h
index e51646ff279e..c3fcd571e446 100644
--- a/drivers/opp/opp.h
+++ b/drivers/opp/opp.h
@@ -212,7 +212,7 @@ struct opp_table {
 
 /* Routines internal to opp core */
 void dev_pm_opp_get(struct dev_pm_opp *opp);
-void _opp_remove_all_static(struct opp_table *opp_table);
+bool _opp_remove_all_static(struct opp_table *opp_table);
 void _get_opp_table_kref(struct opp_table *opp_table);
 int _get_opp_count(struct opp_table *opp_table);
 struct opp_table *_find_opp_table(struct device *dev);
-- 
2.25.0.rc1.19.g042ed3e048af