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

[Viresh Kumar]

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 
> Cc: "Rafael J. Wysocki" 
> Cc: Viresh Kumar 
> Cc: linuxppc-dev@lists.ozlabs.org
> Cc: linux...@vger.kernel.org
> Cc: linux-ker...@vger.kernel.org
> ---
> 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, );
>   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

[PATCH v2] 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: a9acc26b75f ("cpufreq/pasemi: fix possible object reference leak")
Signed-off-by: Wen Yang 
Cc: "Rafael J. Wysocki" 
Cc: Viresh Kumar 
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux...@vger.kernel.org
Cc: linux-ker...@vger.kernel.org
---
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;
err = of_address_to_resource(dn, 0, );
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