releases/4.14.69/cpufreq-governor-avoid-accessing-invalid-governor_data.patch

   1 From 2a3eb51e30b9ac66fe1b75877627a7e4aaeca24a Mon Sep 17 00:00:00 2001
   2 From: Henry Willard <henry.willard@oracle.com>
   3 Date: Tue, 14 Aug 2018 17:01:02 -0700
   4 Subject: cpufreq: governor: Avoid accessing invalid governor_data
   5
   6 From: Henry Willard <henry.willard@oracle.com>
   7
   8 commit 2a3eb51e30b9ac66fe1b75877627a7e4aaeca24a upstream.
   9
  10 If cppc_cpufreq.ko is deleted at the same time that tuned-adm is
  11 changing profiles, there is a small chance that a race can occur
  12 between cpufreq_dbs_governor_exit() and cpufreq_dbs_governor_limits()
  13 resulting in a system failure when the latter tries to use
  14 policy->governor_data that has been freed by the former.
  15
  16 This patch uses gov_dbs_data_mutex to synchronize access.
  17
  18 Fixes: e788892ba3cc (cpufreq: governor: Get rid of governor events)
  19 Signed-off-by: Henry Willard <henry.willard@oracle.com>
  20 [ rjw: Subject, minor white space adjustment ]
  21 Cc: 4.8+ <stable@vger.kernel.org> # 4.8+
  22 Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
  23 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  24
  25 ---
  26  drivers/cpufreq/cpufreq_governor.c |   12 ++++++++++--
  27  1 file changed, 10 insertions(+), 2 deletions(-)
  28
  29 --- a/drivers/cpufreq/cpufreq_governor.c
  30 +++ b/drivers/cpufreq/cpufreq_governor.c
  31 @@ -555,12 +555,20 @@ EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_s
  32
  33  void cpufreq_dbs_governor_limits(struct cpufreq_policy *policy)
  34  {
  35 -       struct policy_dbs_info *policy_dbs = policy->governor_data;
  36 +       struct policy_dbs_info *policy_dbs;
  37 +
  38 +       /* Protect gov->gdbs_data against cpufreq_dbs_governor_exit() */
  39 +       mutex_lock(&gov_dbs_data_mutex);
  40 +       policy_dbs = policy->governor_data;
  41 +       if (!policy_dbs)
  42 +               goto out;
  43
  44         mutex_lock(&policy_dbs->update_mutex);
  45         cpufreq_policy_apply_limits(policy);
  46         gov_update_sample_delay(policy_dbs, 0);
  47 -
  48         mutex_unlock(&policy_dbs->update_mutex);
  49 +
  50 +out:
  51 +       mutex_unlock(&gov_dbs_data_mutex);
  52  }
  53  EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_limits);