From 737ffb27f2f1a8fe6644cac535486f7f25bbf6cb Mon Sep 17 00:00:00 2001 From: Viresh Kumar Date: Tue, 22 Oct 2019 15:47:57 +0530 Subject: cpufreq: Clarify the comment in cpufreq_set_policy() One of the responsibility of the ->verify() callback is to make sure that the policy's min frequency is <= max frequency as this isn't guaranteed by the QoS framework which gave us those values. Update the comment in cpufreq_set_policy() to clarify that. Suggested-by: Rafael J. Wysocki Signed-off-by: Viresh Kumar [ rjw: Minor changes of the new comment ] Signed-off-by: Rafael J. Wysocki --- drivers/cpufreq/cpufreq.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'drivers/cpufreq/cpufreq.c') diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 48a224a6b178..dd1628192310 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -2385,7 +2385,10 @@ int cpufreq_set_policy(struct cpufreq_policy *policy, new_policy->min = freq_qos_read_value(&policy->constraints, FREQ_QOS_MIN); new_policy->max = freq_qos_read_value(&policy->constraints, FREQ_QOS_MAX); - /* verify the cpu speed can be set within this limit */ + /* + * Verify that the CPU speed can be set within these limits and make sure + * that min <= max. + */ ret = cpufreq_driver->verify(new_policy); if (ret) return ret; -- cgit From e6e8df07268c1f75dd9215536e2ce4587b70f977 Mon Sep 17 00:00:00 2001 From: Kai Shen Date: Thu, 7 Nov 2019 05:08:17 +0000 Subject: cpufreq: Add NULL checks to show() and store() methods of cpufreq Add NULL checks to show() and store() in cpufreq.c to avoid attempts to invoke a NULL callback. Though some interfaces of cpufreq are set as read-only, users can still get write permission using chmod which can lead to a kernel crash, as follows: chmod +w /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq echo 1 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq This bug was found in linux 4.19. Signed-off-by: Kai Shen Reported-by: Feilong Lin Reviewed-by: Feilong Lin Acked-by: Viresh Kumar [ rjw: Subject & changelog ] Cc: All applicable Signed-off-by: Rafael J. Wysocki --- drivers/cpufreq/cpufreq.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'drivers/cpufreq/cpufreq.c') diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index dd1628192310..0a10cf9d0b1a 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -933,6 +933,9 @@ static ssize_t show(struct kobject *kobj, struct attribute *attr, char *buf) struct freq_attr *fattr = to_attr(attr); ssize_t ret; + if (!fattr->show) + return -EIO; + down_read(&policy->rwsem); ret = fattr->show(policy, buf); up_read(&policy->rwsem); @@ -947,6 +950,9 @@ static ssize_t store(struct kobject *kobj, struct attribute *attr, struct freq_attr *fattr = to_attr(attr); ssize_t ret = -EINVAL; + if (!fattr->store) + return -EIO; + /* * cpus_read_trylock() is used here to work around a circular lock * dependency problem with respect to the cpufreq_register_driver(). -- cgit From 46770be0cf94149ca48be87719bda1d951066644 Mon Sep 17 00:00:00 2001 From: Viresh Kumar Date: Thu, 14 Nov 2019 09:06:17 +0530 Subject: cpufreq: Register drivers only after CPU devices have been registered The cpufreq core heavily depends on the availability of the struct device for CPUs and if they aren't available at the time cpufreq driver is registered, we will never succeed in making cpufreq work. This happens due to following sequence of events: - cpufreq_register_driver() - subsys_interface_register() - return 0; //successful registration of driver ... at a later point of time - register_cpu(); - device_register(); - bus_probe_device(); - sif->add_dev(); - cpufreq_add_dev(); - get_cpu_device(); //FAILS - per_cpu(cpu_sys_devices, num) = &cpu->dev; //used by get_cpu_device() - return 0; //CPU registered successfully Because the per-cpu variable cpu_sys_devices is set only after the CPU device is regsitered, cpufreq will never be able to get it when cpufreq_add_dev() is called. This patch avoids this failure by making sure device structure of at least CPU0 is available when the cpufreq driver is registered, else return -EPROBE_DEFER. Reported-by: Bjorn Andersson Co-developed-by: Amit Kucheria Signed-off-by: Viresh Kumar Tested-by: Amit Kucheria Signed-off-by: Rafael J. Wysocki --- drivers/cpufreq/cpufreq.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'drivers/cpufreq/cpufreq.c') diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 0a10cf9d0b1a..7fc1a686f2f6 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -2637,6 +2637,13 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data) if (cpufreq_disabled()) return -ENODEV; + /* + * The cpufreq core depends heavily on the availability of device + * structure, make sure they are available before proceeding further. + */ + if (!get_cpu_device(0)) + return -EPROBE_DEFER; + if (!driver_data || !driver_data->verify || !driver_data->init || !(driver_data->setpolicy || driver_data->target_index || driver_data->target) || -- cgit