linux-kernel - [PATCH v3] cpufreq/pasemi: fix an use-after-free in pas_cpufreq_cpu

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Date:   Mon, 8 Jul 2019 16:48:46 +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>,
        linuxppc-dev@...ts.ozlabs.org, linux-pm@...r.kernel.org
Subject: [PATCH v3] 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: linuxppc-dev@...ts.ozlabs.org
Cc: linux-pm@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
---
v3: fix a leaked reference.
v2: clean up the code according to the advice of viresh.

 drivers/cpufreq/pasemi-cpufreq.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/cpufreq/pasemi-cpufreq.c b/drivers/cpufreq/pasemi-cpufreq.c
index 6b1e4ab..9dc5163 100644
--- a/drivers/cpufreq/pasemi-cpufreq.c
+++ b/drivers/cpufreq/pasemi-cpufreq.c
@@ -128,20 +128,20 @@ static int pas_cpufreq_cpu_init(struct cpufreq_policy *policy)
 	int cur_astate, idx;
 	struct resource res;
 	struct device_node *cpu, *dn;
-	int err = -ENODEV;
+	int err;
 
 	cpu = of_get_cpu_node(policy->cpu, NULL);
-
-	of_node_put(cpu);
 	if (!cpu)
-		goto out;
+		return -ENODEV;
 
 	dn = of_find_compatible_node(NULL, NULL, "1682m-sdc");
 	if (!dn)
 		dn = of_find_compatible_node(NULL, NULL,
 					     "pasemi,pwrficient-sdc");
-	if (!dn)
+	if (!dn) {
+		err = -ENODEV;
 		goto out;
+	}
 	err = of_address_to_resource(dn, 0, &res);
 	of_node_put(dn);
 	if (err)
@@ -196,6 +196,7 @@ static int pas_cpufreq_cpu_init(struct cpufreq_policy *policy)
 	policy->cur = pas_freqs[cur_astate].frequency;
 	ppc_proc_freq = policy->cur * 1000ul;
 
+	of_node_put(cpu);
 	return cpufreq_generic_init(policy, pas_freqs, get_gizmo_latency());
 
 out_unmap_sdcpwr:
@@ -204,6 +205,7 @@ static int pas_cpufreq_cpu_init(struct cpufreq_policy *policy)
 out_unmap_sdcasr:
 	iounmap(sdcasr_mapbase);
 out:
+	of_node_put(cpu);
 	return err;
 }
 
-- 
2.9.5