Wen Yang <wen.yan...@zte.com.cn> writes:
> 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.yan...@zte.com.cn>
> Cc: "Rafael J. Wysocki" <r...@rjwysocki.net>
> Cc: Viresh Kumar <viresh.ku...@linaro.org>
> Cc: linuxppc-...@lists.ozlabs.org
> Cc: linux...@vger.kernel.org
> Cc: linux-kernel@vger.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;
I don't think introducing another exit path is an improvement.
> 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;
> }
Notice that cpu is only used for the max_freq calculation, so we could
instead do:
diff --git a/drivers/cpufreq/pasemi-cpufreq.c b/drivers/cpufreq/pasemi-cpufreq.c
index 6b1e4abe3248..42a0a4b8e87d 100644
--- a/drivers/cpufreq/pasemi-cpufreq.c
+++ b/drivers/cpufreq/pasemi-cpufreq.c
@@ -131,11 +131,20 @@ 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);
+ if (!max_freqp) {
+ of_node_put(cpu);
+ err = -EINVAL;
+ goto out;
+ }
+
+ /* we need the freq in kHz */
+ max_freq = *max_freqp / 1000;
+ of_node_put(cpu);
+
dn = of_find_compatible_node(NULL, NULL, "1682m-sdc");
if (!dn)
dn = of_find_compatible_node(NULL, NULL,
@@ -172,15 +181,6 @@ 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");
Though arguably this function should hold a reference to cpu anyway,
because it doesn't want the CPU to removed out from under it. It's a
CPUfreq driver after all.
cheers
