diff options
author | Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> | 2013-09-12 01:43:42 +0530 |
---|---|---|
committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2013-09-11 23:29:57 +0200 |
commit | cb38ed5cf1c4fdb7454e4b48fb70c396f5acfb21 (patch) | |
tree | fd8e6968ee8ba83295f6fe0761e30d939d1eb283 /drivers/cpufreq | |
parent | 61173f256a3bebfbd09b4bd2c164dde378614091 (diff) |
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')
-rw-r--r-- | drivers/cpufreq/cpufreq.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 247842b2ee2..d32040cc1c4 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; |