On 06-01-20, 17:44, qiwuchen55@xxxxxxxxx wrote:
> From: chenqiwu <chenqiwu@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>
> ---
> 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
