If policy initialization fails after the sysfs files are created,
there is a possibility that we may end up running show()/store()
callbacks for half initialized policies, which may have unpredictable
outcomes.
Abort show/store in such a case by making sure the policy is active.
Also inactivate the policy on such failures.
Signed-off-by: Schspa Shi <[email protected]>
---
Changelog:
v1 -> v2:
- Fix bad critical region enlarge which causes uninitialized
unlock.
- Move cpumask_clear(policy->cpus); before out_offline_policy
v2 -> v3:
- Remove the missed down_write() before
cpumask_and(policy->cpus, policy->cpus, cpu_online_mask);
v3 -> v4:
- Seprate to two patchs.
- Add policy_is_inactive check before sysfs access
v4 -> v5:
- Change the commit message as Viresh advised.
- Initialize ret to -EBUSY to get rid of the else part.
v5 -> v6:
- Change up_write(&policy->rwsem); to after out_free_policy;
- Fixes: https://lore.kernel.org/all/20220515095313.GE10578@xsang-OptiPlex-9020/
Signed-off-by: Schspa Shi <[email protected]>
---
drivers/cpufreq/cpufreq.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 80f535cc8a75..ba73be6f0490 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -947,13 +947,14 @@ static ssize_t show(struct kobject *kobj, struct attribute *attr, char *buf)
{
struct cpufreq_policy *policy = to_policy(kobj);
struct freq_attr *fattr = to_attr(attr);
- ssize_t ret;
+ ssize_t ret = -EBUSY;
if (!fattr->show)
return -EIO;
down_read(&policy->rwsem);
- ret = fattr->show(policy, buf);
+ if (likely(!policy_is_inactive(policy)))
+ ret = fattr->show(policy, buf);
up_read(&policy->rwsem);
return ret;
@@ -964,7 +965,7 @@ static ssize_t store(struct kobject *kobj, struct attribute *attr,
{
struct cpufreq_policy *policy = to_policy(kobj);
struct freq_attr *fattr = to_attr(attr);
- ssize_t ret = -EINVAL;
+ ssize_t ret = -EBUSY;
if (!fattr->store)
return -EIO;
@@ -978,7 +979,8 @@ static ssize_t store(struct kobject *kobj, struct attribute *attr,
if (cpu_online(policy->cpu)) {
down_write(&policy->rwsem);
- ret = fattr->store(policy, buf, count);
+ if (likely(!policy_is_inactive(policy)))
+ ret = fattr->store(policy, buf, count);
up_write(&policy->rwsem);
}
@@ -1533,6 +1535,7 @@ static int cpufreq_online(unsigned int cpu)
for_each_cpu(j, policy->real_cpus)
remove_cpu_dev_symlink(policy, get_cpu_device(j));
+ cpumask_clear(policy->cpus);
up_write(&policy->rwsem);
out_offline_policy:
--
2.29.0
cpufreq_offline() calls offline() and exit() under the policy rwsem
But they are called outside the rwsem in cpufreq_online().
This patch move the offline(), exit(), online(), init() to be inside
of policy rwsem to achieve a clear lock relationship.
All the init() online() implement only initialize policy object without
holding this lock and won't call cpufreq APIs need to hold this lock.
Signed-off-by: Schspa Shi <[email protected]>
---
drivers/cpufreq/cpufreq.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index ba73be6f0490..ccb774e02934 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1339,12 +1339,12 @@ static int cpufreq_online(unsigned int cpu)
down_write(&policy->rwsem);
policy->cpu = cpu;
policy->governor = NULL;
- up_write(&policy->rwsem);
} else {
new_policy = true;
policy = cpufreq_policy_alloc(cpu);
if (!policy)
return -ENOMEM;
+ down_write(&policy->rwsem);
}
if (!new_policy && cpufreq_driver->online) {
@@ -1384,7 +1384,6 @@ static int cpufreq_online(unsigned int cpu)
cpumask_copy(policy->related_cpus, policy->cpus);
}
- down_write(&policy->rwsem);
/*
* affected cpus must always be the one, which are online. We aren't
* managing offline cpus here.
@@ -1536,7 +1535,6 @@ static int cpufreq_online(unsigned int cpu)
remove_cpu_dev_symlink(policy, get_cpu_device(j));
cpumask_clear(policy->cpus);
- up_write(&policy->rwsem);
out_offline_policy:
if (cpufreq_driver->offline)
@@ -1547,6 +1545,8 @@ static int cpufreq_online(unsigned int cpu)
cpufreq_driver->exit(policy);
out_free_policy:
+ up_write(&policy->rwsem);
+
cpufreq_policy_free(policy);
return ret;
}
--
2.29.0
On Mon, 16 May 2022 at 04:12, Schspa Shi <[email protected]> wrote:
>
> cpufreq_offline() calls offline() and exit() under the policy rwsem
> But they are called outside the rwsem in cpufreq_online().
>
> This patch move the offline(), exit(), online(), init() to be inside
> of policy rwsem to achieve a clear lock relationship.
>
> All the init() online() implement only initialize policy object without
> holding this lock and won't call cpufreq APIs need to hold this lock.
>
> Signed-off-by: Schspa Shi <[email protected]>
> ---
> drivers/cpufreq/cpufreq.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
Acked-by: Viresh Kumar <[email protected]>
On Mon, 16 May 2022 at 04:03, Schspa Shi <[email protected]> wrote:
>
> If policy initialization fails after the sysfs files are created,
> there is a possibility that we may end up running show()/store()
> callbacks for half initialized policies, which may have unpredictable
> outcomes.
>
> Abort show/store in such a case by making sure the policy is active.
> Also inactivate the policy on such failures.
>
> Signed-off-by: Schspa Shi <[email protected]>
Acked-by: Viresh Kumar <[email protected]>
On Mon, May 16, 2022 at 12:25 PM Viresh Kumar <[email protected]> wrote:
>
> On Mon, 16 May 2022 at 04:03, Schspa Shi <[email protected]> wrote:
> >
> > If policy initialization fails after the sysfs files are created,
> > there is a possibility that we may end up running show()/store()
> > callbacks for half initialized policies, which may have unpredictable
> > outcomes.
> >
> > Abort show/store in such a case by making sure the policy is active.
> > Also inactivate the policy on such failures.
> >
> > Signed-off-by: Schspa Shi <[email protected]>
>
> Acked-by: Viresh Kumar <[email protected]>
Applied along with the [2/2], with some adjustments in the subject and
changelog, as 5.19 material.
Thanks!