Re: [PATCH v2] cpufreq/pasemi: fix an use-after-free in pas_cpufreq_cpu_init()

From: Viresh Kumar
Date: Mon Jul 08 2019 - 03:44:40 EST


On 08-07-19, 15:19, Wen Yang wrote:
> 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@xxxxxxxxxx>
> Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
> Cc: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
> Cc: linux-pm@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> ---
> v2: clean up the code according to the advice of viresh.
>
> drivers/cpufreq/pasemi-cpufreq.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/cpufreq/pasemi-cpufreq.c b/drivers/cpufreq/pasemi-cpufreq.c
> index 6b1e4ab..c6d464b 100644
> --- a/drivers/cpufreq/pasemi-cpufreq.c
> +++ b/drivers/cpufreq/pasemi-cpufreq.c
> @@ -128,20 +128,18 @@ 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)
> - goto out;
> + return -ENODEV;

This change looks incorrect. You still need to drop reference to cpu ?

> err = of_address_to_resource(dn, 0, &res);
> of_node_put(dn);
> if (err)
> @@ -196,6 +194,7 @@ 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 +203,7 @@ 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

--
viresh