linux-kernel - [PATCH 3/5] PM / devfreq: Fix kernel panic with cpu based scaling to passive gov

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Date:   Mon,  6 Jun 2022 13:11:02 +0200
From:   Christian 'Ansuel' Marangi <ansuelsmth@...il.com>
To:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Saravana Kannan <skannan@...eaurora.org>,
        Sibi Sankar <sibis@...eaurora.org>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Christian 'Ansuel' Marangi <ansuelsmth@...il.com>
Subject: [PATCH 3/5] PM / devfreq: Fix kernel panic with cpu based scaling to passive gov

The cpufreq passive register notifier can PROBE_DEFER and the devfreq
struct is freed and then reallocaed on probe retry.
The current logic assume that the code can't PROBE_DEFER so the devfreq
struct in the this variable in devfreq_passive_data is assumed to be
(if already set) always correct.
This cause kernel panic as the code try to access the wrong address.
To correctly handle this, update the this variable in
devfreq_passive_data to the devfreq reallocated struct.

Fixes: a03dacb0316f ("PM / devfreq: Add cpu based scaling support to passive governor")
Signed-off-by: Christian 'Ansuel' Marangi <ansuelsmth@...il.com>
---
 drivers/devfreq/governor_passive.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/devfreq/governor_passive.c b/drivers/devfreq/governor_passive.c
index ab393c8174f4..528c8f3b25f0 100644
--- a/drivers/devfreq/governor_passive.c
+++ b/drivers/devfreq/governor_passive.c
@@ -395,8 +395,7 @@ static int devfreq_passive_event_handler(struct devfreq *devfreq,
 	if (!p_data)
 		return -EINVAL;
 
-	if (!p_data->this)
-		p_data->this = devfreq;
+	p_data->this = devfreq;
 
 	switch (event) {
 	case DEVFREQ_GOV_START:
-- 
2.36.1