[PATCH] ACPI: processor: Avoid NULL pointer dereferences at init time

Rafael J. Wysocki
2019-10-15T17:35:24Z

rom: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

If there are neither processor objects nor processor device objects
in the ACPI tables, the per-CPU processors table will not be
initialized and attempting to dereference pointers from there will
cause the kernel to crash. This happens in acpi_processor_ppc_init()
and acpi_thermal_cpufreq_init() after commit d15ce412737a ("ACPI:
cpufreq: Switch to QoS requests instead of cpufreq notifier")
which didn't add the requisite NULL pointer checks in there.

Add the NULL pointer checks to acpi_processor_ppc_init() and
acpi_thermal_cpufreq_init(), and to the corresponding "exit"
routines.

While at it, drop redundant return instructions from
acpi_processor_ppc_init() and acpi_thermal_cpufreq_init().

Fixes: d15ce412737a ("ACPI: cpufreq: Switch to QoS requests instead of cpufreq notifier")
Reported-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
drivers/acpi/processor_perflib.c | 10 ++++++----
drivers/acpi/processor_thermal.c | 10 ++++++----
2 files changed, 12 insertions(+), 8 deletions(-)

Index: linux-pm/drivers/acpi/processor_perflib.c
===================================================================
--- linux-pm.orig/drivers/acpi/processor_perflib.c
+++ linux-pm/drivers/acpi/processor_perflib.c
@@ -162,21 +162,23 @@ void acpi_processor_ppc_init(int cpu)
struct acpi_processor *pr = per_cpu(processors, cpu);
int ret;

+ if (!pr)
+ return;
+
ret = dev_pm_qos_add_request(get_cpu_device(cpu),
&pr->perflib_req, DEV_PM_QOS_MAX_FREQUENCY,
INT_MAX);
- if (ret < 0) {
+ if (ret < 0)
pr_err("Failed to add freq constraint for CPU%d (%d)\n", cpu,
ret);
- return;
- }
}

void acpi_processor_ppc_exit(int cpu)
{
struct acpi_processor *pr = per_cpu(processors, cpu);

- dev_pm_qos_remove_request(&pr->perflib_req);
+ if (pr)
+ dev_pm_qos_remove_request(&pr->perflib_req);
}

static int acpi_processor_get_performance_control(struct acpi_processor *pr)
Index: linux-pm/drivers/acpi/processor_thermal.c
===================================================================
--- linux-pm.orig/drivers/acpi/processor_thermal.c
+++ linux-pm/drivers/acpi/processor_thermal.c
@@ -130,21 +130,23 @@ void acpi_thermal_cpufreq_init(int cpu)
struct acpi_processor *pr = per_cpu(processors, cpu);
int ret;

+ if (!pr)
+ return;
+
ret = dev_pm_qos_add_request(get_cpu_device(cpu),
&pr->thermal_req, DEV_PM_QOS_MAX_FREQUENCY,
INT_MAX);
- if (ret < 0) {
+ if (ret < 0)
pr_err("Failed to add freq constraint for CPU%d (%d)\n", cpu,
ret);
- return;
- }
}

void acpi_thermal_cpufreq_exit(int cpu)
{
struct acpi_processor *pr = per_cpu(processors, cpu);

- dev_pm_qos_remove_request(&pr->thermal_req);
+ if (pr)
+ dev_pm_qos_remove_request(&pr->thermal_req);
}
#else /* ! CONFIG_CPU_FREQ */
static int cpufreq_get_max_state(unsigned int cpu)