linux-kernel - [PATCH v5] cpufreq/pasemi: fix an use-after-free in pas_cpufreq_cpu

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Date:   Tue, 9 Jul 2019 16:04:07 +0800
From:   Wen Yang <wen.yang99@....com.cn>
To:     linux-kernel@...r.kernel.org
Cc:     xue.zhihong@....com.cn, wang.yi59@....com.cn,
        cheng.shengyu@....com.cn, Wen Yang <wen.yang99@....com.cn>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        linuxppc-dev@...ts.ozlabs.org, linux-pm@...r.kernel.org
Subject: [PATCH v5] cpufreq/pasemi: fix an use-after-free in pas_cpufreq_cpu_init()

The cpu variable is still being used in the of_get_property() call
after the of_node_put() call, which may result in use-after-free.

Fixes: a9acc26b75f ("cpufreq/pasemi: fix possible object reference leak")
Signed-off-by: Wen Yang <wen.yang99@....com.cn>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: Viresh Kumar <viresh.kumar@...aro.org>
Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: linuxppc-dev@...ts.ozlabs.org
Cc: linux-pm@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
---
v5: put together the code to get, use, and release cpu device_node.
v4: restore the blank line.
v3: fix a leaked reference.
v2: clean up the code according to the advice of viresh.

 drivers/cpufreq/pasemi-cpufreq.c | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/drivers/cpufreq/pasemi-cpufreq.c b/drivers/cpufreq/pasemi-cpufreq.c
index 6b1e4ab..1f0beb7 100644
--- a/drivers/cpufreq/pasemi-cpufreq.c
+++ b/drivers/cpufreq/pasemi-cpufreq.c
@@ -131,10 +131,17 @@ static int pas_cpufreq_cpu_init(struct cpufreq_policy *policy)
 	int err = -ENODEV;
 
 	cpu = of_get_cpu_node(policy->cpu, NULL);
-
-	of_node_put(cpu);
 	if (!cpu)
 		goto out;
+	max_freqp = of_get_property(cpu, "clock-frequency", NULL);
+	of_node_put(cpu);
+	if (!max_freqp) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	/* we need the freq in kHz */
+	max_freq = *max_freqp / 1000;
 
 	dn = of_find_compatible_node(NULL, NULL, "1682m-sdc");
 	if (!dn)
@@ -171,16 +178,6 @@ static int pas_cpufreq_cpu_init(struct cpufreq_policy *policy)
 	}
 
 	pr_debug("init cpufreq on CPU %d\n", policy->cpu);
-
-	max_freqp = of_get_property(cpu, "clock-frequency", NULL);
-	if (!max_freqp) {
-		err = -EINVAL;
-		goto out_unmap_sdcpwr;
-	}
-
-	/* we need the freq in kHz */
-	max_freq = *max_freqp / 1000;
-
 	pr_debug("max clock-frequency is at %u kHz\n", max_freq);
 	pr_debug("initializing frequency table\n");
 
-- 
2.9.5