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authorDmitry Monakhov <dmonakhov@openvz.org>2009-10-05 00:38:55 +0400
committerDave Jones <davej@redhat.com>2009-11-17 23:15:04 -0500
commite77b89f13a0d48aea70b69976e854f2a2444a519 (patch)
treed78288fc4386e1613713fff8c13d28f7ec480d32
parent293afe44d75abce4252db76cbb303a7de4297ce1 (diff)
downloadlinux-e77b89f13a0d48aea70b69976e854f2a2444a519.tar.bz2
[CPUFREQ] Fix use after free on governor restore
Currently on governer backup/restore path we storing governor's pointer. This is wrong because one may unload governor's module after cpu goes offline. As result use-after-free will take place on restored cpu. It is not easy to exploit this bug, but still we have to close this issue ASAP. Issue was introduced by following commit 084f34939424161669467c19280dbcf637730314 ##TESTCASE## #!/bin/sh -x modprobe acpi_cpufreq # Any non default governor, in may case it is "ondemand" modprobe cpufreq_ondemand echo ondemand > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor rmmod acpi_cpufreq rmmod cpufreq_ondemand modprobe acpi_cpufreq # << use-after-free here. Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org> Signed-off-by: Dave Jones <davej@redhat.com>
-rw-r--r--drivers/cpufreq/cpufreq.c16
1 files changed, 10 insertions, 6 deletions
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 3938c7817095..dab1410d1c0d 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -41,7 +41,7 @@ static struct cpufreq_driver *cpufreq_driver;
static DEFINE_PER_CPU(struct cpufreq_policy *, cpufreq_cpu_data);
#ifdef CONFIG_HOTPLUG_CPU
/* This one keeps track of the previously set governor of a removed CPU */
-static DEFINE_PER_CPU(struct cpufreq_governor *, cpufreq_cpu_governor);
+static DEFINE_PER_CPU(char[CPUFREQ_NAME_LEN], cpufreq_cpu_governor);
#endif
static DEFINE_SPINLOCK(cpufreq_driver_lock);
@@ -774,10 +774,12 @@ int cpufreq_add_dev_policy(unsigned int cpu, struct cpufreq_policy *policy,
#ifdef CONFIG_SMP
unsigned long flags;
unsigned int j;
-
#ifdef CONFIG_HOTPLUG_CPU
- if (per_cpu(cpufreq_cpu_governor, cpu)) {
- policy->governor = per_cpu(cpufreq_cpu_governor, cpu);
+ struct cpufreq_governor *gov;
+
+ gov = __find_governor(per_cpu(cpufreq_cpu_governor, cpu));
+ if (gov) {
+ policy->governor = gov;
dprintk("Restoring governor %s for cpu %d\n",
policy->governor->name, cpu);
}
@@ -1111,7 +1113,8 @@ static int __cpufreq_remove_dev(struct sys_device *sys_dev)
#ifdef CONFIG_SMP
#ifdef CONFIG_HOTPLUG_CPU
- per_cpu(cpufreq_cpu_governor, cpu) = data->governor;
+ strncpy(per_cpu(cpufreq_cpu_governor, cpu), data->governor->name,
+ CPUFREQ_NAME_LEN);
#endif
/* if we have other CPUs still registered, we need to unlink them,
@@ -1135,7 +1138,8 @@ static int __cpufreq_remove_dev(struct sys_device *sys_dev)
continue;
dprintk("removing link for cpu %u\n", j);
#ifdef CONFIG_HOTPLUG_CPU
- per_cpu(cpufreq_cpu_governor, j) = data->governor;
+ strncpy(per_cpu(cpufreq_cpu_governor, j),
+ data->governor->name, CPUFREQ_NAME_LEN);
#endif
cpu_sys_dev = get_cpu_sysdev(j);
sysfs_remove_link(&cpu_sys_dev->kobj, "cpufreq");