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authorSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>2013-09-12 00:13:42 +0400
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2013-09-12 01:29:57 +0400
commitcb38ed5cf1c4fdb7454e4b48fb70c396f5acfb21 (patch)
treefd8e6968ee8ba83295f6fe0761e30d939d1eb283 /drivers/cpufreq/cpufreq.c
parent61173f256a3bebfbd09b4bd2c164dde378614091 (diff)
downloadlinux-cb38ed5cf1c4fdb7454e4b48fb70c396f5acfb21.tar.xz
cpufreq: Prevent problems in update_policy_cpu() if last_cpu == new_cpu
If update_policy_cpu() is invoked with the existing policy->cpu itself as the new-cpu parameter, then a lot of things can go terribly wrong. In its present form, update_policy_cpu() always assumes that the new-cpu is different from policy->cpu and invokes other functions to perform their respective updates. And those functions implement the actual update like this: per_cpu(..., new_cpu) = per_cpu(..., last_cpu); per_cpu(..., last_cpu) = NULL; Thus, when new_cpu == last_cpu, the final NULL assignment makes the per-cpu references vanish into thin air! (memory leak). From there, it leads to more problems: cpufreq_stats_create_table() now doesn't find the per-cpu reference and hence tries to create a new sysfs-group; but sysfs already had created the group earlier, so it complains that it cannot create a duplicate filename. In short, the repercussions of a rather innocuous invocation of update_policy_cpu() can turn out to be pretty nasty. Ideally update_policy_cpu() should handle this situation (new == last) gracefully, and not lead to such severe problems. So fix it by adding an appropriate check. Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Tested-by: Stephen Warren <swarren@nvidia.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/cpufreq/cpufreq.c')
-rw-r--r--drivers/cpufreq/cpufreq.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 247842b2ee2d..d32040cc1c46 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -949,6 +949,9 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy)
static void update_policy_cpu(struct cpufreq_policy *policy, unsigned int cpu)
{
+ if (cpu == policy->cpu)
+ return;
+
policy->last_cpu = policy->cpu;
policy->cpu = cpu;