[v2] cpufreq: s3c: avoid use after free issue in xxx_cpufreq_reboot_notifier_evt()
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Message ID 1578303861-7217-1-git-send-email-qiwuchen55@gmail.com
State Not Applicable
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  • [v2] cpufreq: s3c: avoid use after free issue in xxx_cpufreq_reboot_notifier_evt()
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Commit Message

chenqiwu Jan. 6, 2020, 9:44 a.m. UTC
From: chenqiwu <chenqiwu@xiaomi.com>

There is a potential UAF issue in xxx_cpufreq_reboot_notifier_evt() that
the cpufreq policy of cpu0 has been released before using it. So we should
make a judgement to avoid it.

Signed-off-by: chenqiwu <chenqiwu@xiaomi.com>
---
changes in v2:
 - use the combination of cpufreq_cpu_get() and cpufreq_cpu_put()
   instead of cpufreq_get_policy() in s3c2416-cpufreq.c
---
 drivers/cpufreq/s3c2416-cpufreq.c | 12 +++++++++++-
 drivers/cpufreq/s5pv210-cpufreq.c | 11 ++++++++++-
 2 files changed, 21 insertions(+), 2 deletions(-)

Comments

Viresh Kumar Jan. 7, 2020, 5:31 a.m. UTC | #1
On 06-01-20, 17:44, qiwuchen55@gmail.com wrote:
> From: chenqiwu <chenqiwu@xiaomi.com>
> 
> There is a potential UAF issue in xxx_cpufreq_reboot_notifier_evt() that
> the cpufreq policy of cpu0 has been released before using it. So we should
> make a judgement to avoid it.

Again, the subject and description are incorrect here. This isn't a user after
free problem as we were already calling cpufreq_cpu_get(). The problem was that
the balancing of refcount wasn't done properly.


> Signed-off-by: chenqiwu <chenqiwu@xiaomi.com>
> ---
> changes in v2:
>  - use the combination of cpufreq_cpu_get() and cpufreq_cpu_put()
>    instead of cpufreq_get_policy() in s3c2416-cpufreq.c
> ---
>  drivers/cpufreq/s3c2416-cpufreq.c | 12 +++++++++++-
>  drivers/cpufreq/s5pv210-cpufreq.c | 11 ++++++++++-
>  2 files changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cpufreq/s3c2416-cpufreq.c b/drivers/cpufreq/s3c2416-cpufreq.c
> index 1069103..f07c5d1 100644
> --- a/drivers/cpufreq/s3c2416-cpufreq.c
> +++ b/drivers/cpufreq/s3c2416-cpufreq.c
> @@ -304,6 +304,7 @@ static int s3c2416_cpufreq_reboot_notifier_evt(struct notifier_block *this,
>  {
>  	struct s3c2416_data *s3c_freq = &s3c2416_cpufreq;
>  	int ret;
> +	struct cpufreq_policy *policy;
>  
>  	mutex_lock(&cpufreq_lock);
>  
> @@ -318,7 +319,16 @@ static int s3c2416_cpufreq_reboot_notifier_evt(struct notifier_block *this,
>  	 */
>  	if (s3c_freq->is_dvs) {
>  		pr_debug("cpufreq: leave dvs on reboot\n");
> -		ret = cpufreq_driver_target(cpufreq_cpu_get(0), FREQ_SLEEP, 0);
> +
> +		policy = cpufreq_cpu_get(0);
> +		if (!policy) {
> +			pr_debug("cpufreq: get no policy for cpu0\n");
> +			return NOTIFY_BAD;
> +		}
> +
> +		ret = cpufreq_driver_target(&policy, FREQ_SLEEP, 0);
> +		cpufreq_cpu_put(policy);
> +
>  		if (ret < 0)
>  			return NOTIFY_BAD;
>  	}
> diff --git a/drivers/cpufreq/s5pv210-cpufreq.c b/drivers/cpufreq/s5pv210-cpufreq.c
> index 5d10030..e84281e 100644
> --- a/drivers/cpufreq/s5pv210-cpufreq.c
> +++ b/drivers/cpufreq/s5pv210-cpufreq.c
> @@ -555,8 +555,17 @@ static int s5pv210_cpufreq_reboot_notifier_event(struct notifier_block *this,
>  						 unsigned long event, void *ptr)
>  {
>  	int ret;
> +	struct cpufreq_policy *policy;
> +
> +	policy = cpufreq_cpu_get(0);
> +	if (!policy) {
> +		pr_debug("cpufreq: get no policy for cpu0\n");
> +		return NOTIFY_BAD;
> +	}
> +
> +	ret = cpufreq_driver_target(policy, SLEEP_FREQ, 0);
> +	cpufreq_cpu_put(policy);
>  
> -	ret = cpufreq_driver_target(cpufreq_cpu_get(0), SLEEP_FREQ, 0);
>  	if (ret < 0)
>  		return NOTIFY_BAD;
>  
> -- 
> 1.9.1
chenqiwu Jan. 7, 2020, 7:50 a.m. UTC | #2
On Tue, Jan 07, 2020 at 11:01:47AM +0530, Viresh Kumar wrote:
> On 06-01-20, 17:44, qiwuchen55@gmail.com wrote:
> > From: chenqiwu <chenqiwu@xiaomi.com>
> > 
> > There is a potential UAF issue in xxx_cpufreq_reboot_notifier_evt() that
> > the cpufreq policy of cpu0 has been released before using it. So we should
> > make a judgement to avoid it.
> 
> Again, the subject and description are incorrect here. This isn't a user after
> free problem as we were already calling cpufreq_cpu_get(). The problem was that
> the balancing of refcount wasn't done properly.
> 
>

Yeah, I will rewrite the title and commit message, and resend this as
patch v3.

Thanks!

> > Signed-off-by: chenqiwu <chenqiwu@xiaomi.com>
> > ---
> > changes in v2:
> >  - use the combination of cpufreq_cpu_get() and cpufreq_cpu_put()
> >    instead of cpufreq_get_policy() in s3c2416-cpufreq.c
> > ---
> >  drivers/cpufreq/s3c2416-cpufreq.c | 12 +++++++++++-
> >  drivers/cpufreq/s5pv210-cpufreq.c | 11 ++++++++++-
> >  2 files changed, 21 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/cpufreq/s3c2416-cpufreq.c b/drivers/cpufreq/s3c2416-cpufreq.c
> > index 1069103..f07c5d1 100644
> > --- a/drivers/cpufreq/s3c2416-cpufreq.c
> > +++ b/drivers/cpufreq/s3c2416-cpufreq.c
> > @@ -304,6 +304,7 @@ static int s3c2416_cpufreq_reboot_notifier_evt(struct notifier_block *this,
> >  {
> >  	struct s3c2416_data *s3c_freq = &s3c2416_cpufreq;
> >  	int ret;
> > +	struct cpufreq_policy *policy;
> >  
> >  	mutex_lock(&cpufreq_lock);
> >  
> > @@ -318,7 +319,16 @@ static int s3c2416_cpufreq_reboot_notifier_evt(struct notifier_block *this,
> >  	 */
> >  	if (s3c_freq->is_dvs) {
> >  		pr_debug("cpufreq: leave dvs on reboot\n");
> > -		ret = cpufreq_driver_target(cpufreq_cpu_get(0), FREQ_SLEEP, 0);
> > +
> > +		policy = cpufreq_cpu_get(0);
> > +		if (!policy) {
> > +			pr_debug("cpufreq: get no policy for cpu0\n");
> > +			return NOTIFY_BAD;
> > +		}
> > +
> > +		ret = cpufreq_driver_target(&policy, FREQ_SLEEP, 0);
> > +		cpufreq_cpu_put(policy);
> > +
> >  		if (ret < 0)
> >  			return NOTIFY_BAD;
> >  	}
> > diff --git a/drivers/cpufreq/s5pv210-cpufreq.c b/drivers/cpufreq/s5pv210-cpufreq.c
> > index 5d10030..e84281e 100644
> > --- a/drivers/cpufreq/s5pv210-cpufreq.c
> > +++ b/drivers/cpufreq/s5pv210-cpufreq.c
> > @@ -555,8 +555,17 @@ static int s5pv210_cpufreq_reboot_notifier_event(struct notifier_block *this,
> >  						 unsigned long event, void *ptr)
> >  {
> >  	int ret;
> > +	struct cpufreq_policy *policy;
> > +
> > +	policy = cpufreq_cpu_get(0);
> > +	if (!policy) {
> > +		pr_debug("cpufreq: get no policy for cpu0\n");
> > +		return NOTIFY_BAD;
> > +	}
> > +
> > +	ret = cpufreq_driver_target(policy, SLEEP_FREQ, 0);
> > +	cpufreq_cpu_put(policy);
> >  
> > -	ret = cpufreq_driver_target(cpufreq_cpu_get(0), SLEEP_FREQ, 0);
> >  	if (ret < 0)
> >  		return NOTIFY_BAD;
> >  
> > -- 
> > 1.9.1
> 
> -- 
> viresh

--
Qiwu

Patch
diff mbox series

diff --git a/drivers/cpufreq/s3c2416-cpufreq.c b/drivers/cpufreq/s3c2416-cpufreq.c
index 1069103..f07c5d1 100644
--- a/drivers/cpufreq/s3c2416-cpufreq.c
+++ b/drivers/cpufreq/s3c2416-cpufreq.c
@@ -304,6 +304,7 @@  static int s3c2416_cpufreq_reboot_notifier_evt(struct notifier_block *this,
 {
 	struct s3c2416_data *s3c_freq = &s3c2416_cpufreq;
 	int ret;
+	struct cpufreq_policy *policy;
 
 	mutex_lock(&cpufreq_lock);
 
@@ -318,7 +319,16 @@  static int s3c2416_cpufreq_reboot_notifier_evt(struct notifier_block *this,
 	 */
 	if (s3c_freq->is_dvs) {
 		pr_debug("cpufreq: leave dvs on reboot\n");
-		ret = cpufreq_driver_target(cpufreq_cpu_get(0), FREQ_SLEEP, 0);
+
+		policy = cpufreq_cpu_get(0);
+		if (!policy) {
+			pr_debug("cpufreq: get no policy for cpu0\n");
+			return NOTIFY_BAD;
+		}
+
+		ret = cpufreq_driver_target(&policy, FREQ_SLEEP, 0);
+		cpufreq_cpu_put(policy);
+
 		if (ret < 0)
 			return NOTIFY_BAD;
 	}
diff --git a/drivers/cpufreq/s5pv210-cpufreq.c b/drivers/cpufreq/s5pv210-cpufreq.c
index 5d10030..e84281e 100644
--- a/drivers/cpufreq/s5pv210-cpufreq.c
+++ b/drivers/cpufreq/s5pv210-cpufreq.c
@@ -555,8 +555,17 @@  static int s5pv210_cpufreq_reboot_notifier_event(struct notifier_block *this,
 						 unsigned long event, void *ptr)
 {
 	int ret;
+	struct cpufreq_policy *policy;
+
+	policy = cpufreq_cpu_get(0);
+	if (!policy) {
+		pr_debug("cpufreq: get no policy for cpu0\n");
+		return NOTIFY_BAD;
+	}
+
+	ret = cpufreq_driver_target(policy, SLEEP_FREQ, 0);
+	cpufreq_cpu_put(policy);
 
-	ret = cpufreq_driver_target(cpufreq_cpu_get(0), SLEEP_FREQ, 0);
 	if (ret < 0)
 		return NOTIFY_BAD;