[PATCH v6] cpufreq/pasemi: fix an use-after-free in pas_cpufreq_cpu_init()

[Wen Yang]

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: a9acc26b75f6 ("cpufreq/pasemi: fix possible object reference leak")
Signed-off-by: Wen Yang <wen.yan...@zte.com.cn>
Cc: "Rafael J. Wysocki" <r...@rjwysocki.net>
Cc: Viresh Kumar <viresh.ku...@linaro.org>
Cc: Michael Ellerman <m...@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux...@vger.kernel.org
Cc: linux-ker...@vger.kernel.org
---
v6: keep the blank line and fix warning: label 'out_unmap_sdcpwr' defined but 
not used.
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 | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/drivers/cpufreq/pasemi-cpufreq.c b/drivers/cpufreq/pasemi-cpufreq.c
index 6b1e4ab..7d557f9 100644
--- a/drivers/cpufreq/pasemi-cpufreq.c
+++ b/drivers/cpufreq/pasemi-cpufreq.c
@@ -131,10 +131,18 @@ static int pas_cpufreq_cpu_init(struct cpufreq_policy 
*policy)
        int err = -ENODEV;
 
        cpu = of_get_cpu_node(policy->cpu, NULL);
+       if (!cpu)
+               goto out;
 
+       max_freqp = of_get_property(cpu, "clock-frequency", NULL);
        of_node_put(cpu);
-       if (!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 +179,6 @@ 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");
 
@@ -196,7 +194,11 @@ static int pas_cpufreq_cpu_init(struct cpufreq_policy 
*policy)
        policy->cur = pas_freqs[cur_astate].frequency;
        ppc_proc_freq = policy->cur * 1000ul;
 
-       return cpufreq_generic_init(policy, pas_freqs, get_gizmo_latency());
+       err = cpufreq_generic_init(policy, pas_freqs, get_gizmo_latency());
+       if (err)
+               goto out_unmap_sdcpwr;
+
+       return 0;
 
 out_unmap_sdcpwr:
        iounmap(sdcpwr_mapbase);
-- 
2.9.5