linux-kernel - [tip:smp/hotplug] cpufreq: Fix up conversion to hotplug state machine

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Date:   Tue, 20 Sep 2016 08:07:08 -0700
From:   tip-bot for Sebastian Andrzej Siewior <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, mingo@...nel.org, tglx@...utronix.de,
        hpa@...or.com, bp@...en8.de, bigeasy@...utronix.de
Subject: [tip:smp/hotplug] cpufreq: Fix up conversion to hotplug state
 machine

Commit-ID:  5372e054a1928fe704cf0a5e2e139645a777b50a
Gitweb:     http://git.kernel.org/tip/5372e054a1928fe704cf0a5e2e139645a777b50a
Author:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
AuthorDate: Tue, 20 Sep 2016 16:56:28 +0200
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Tue, 20 Sep 2016 16:59:21 +0200

cpufreq: Fix up conversion to hotplug state machine

The function cpufreq_register_driver() returns zero on success and since
commit 27622b061eb4 ("cpufreq: Convert to hotplug state machine")
erroneously a positive number. Due to the "if (x) assume_error" construct
all callers assumed an error and as a consequence the cpu freq kworker
crashes with a NULL pointer dereference.

Reset the return value back to zero in the success case.

Fixes: 27622b061eb4 ("cpufreq: Convert to hotplug state machine")
Reported-by: Borislav Petkov <bp@...en8.de>
Reported-and-tested-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: peterz@...radead.org
Cc: rjw@...ysocki.net
Link: http://lkml.kernel.org/r/20160920145628.lp2bmq72ip3oiash@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

---
 drivers/cpufreq/cpufreq.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index e0bc632..8b44de4 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -2503,6 +2503,7 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
 	if (ret < 0)
 		goto err_if_unreg;
 	hp_online = ret;
+	ret = 0;
 
 	pr_debug("driver %s up and running\n", driver_data->name);
 	goto out;