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authorViresh Kumar <viresh.kumar@linaro.org>2020-06-29 13:54:58 +0530
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-08-19 08:16:25 +0200
commit613a374f3fd684916972e916bab5fb8f212eb013 (patch)
tree564dade94b71cfed01c2ed0e8eaca8780a5fbe5d
parent6d1e56826ea8ec3ae122ba5c7c815056d5a37655 (diff)
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cpufreq: Fix locking issues with governors
commit 8cc46ae565c393f77417cb9530b1265eb50f5d2e upstream. The locking around governors handling isn't adequate currently. The list of governors should never be traversed without the locking in place. Also governor modules must not be removed while the code in them is still in use. Reported-by: Quentin Perret <qperret@google.com> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> Cc: All applicable <stable@vger.kernel.org> [ rjw: Changelog ] Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/cpufreq/cpufreq.c58
1 files changed, 35 insertions, 23 deletions
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index fa988bd1e606..194a6587a1de 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -616,6 +616,24 @@ static struct cpufreq_governor *find_governor(const char *str_governor)
return NULL;
}
+static struct cpufreq_governor *get_governor(const char *str_governor)
+{
+ struct cpufreq_governor *t;
+
+ mutex_lock(&cpufreq_governor_mutex);
+ t = find_governor(str_governor);
+ if (!t)
+ goto unlock;
+
+ if (!try_module_get(t->owner))
+ t = NULL;
+
+unlock:
+ mutex_unlock(&cpufreq_governor_mutex);
+
+ return t;
+}
+
static unsigned int cpufreq_parse_policy(char *str_governor)
{
if (!strncasecmp(str_governor, "performance", CPUFREQ_NAME_LEN))
@@ -635,28 +653,14 @@ static struct cpufreq_governor *cpufreq_parse_governor(char *str_governor)
{
struct cpufreq_governor *t;
- mutex_lock(&cpufreq_governor_mutex);
+ t = get_governor(str_governor);
+ if (t)
+ return t;
- t = find_governor(str_governor);
- if (!t) {
- int ret;
-
- mutex_unlock(&cpufreq_governor_mutex);
-
- ret = request_module("cpufreq_%s", str_governor);
- if (ret)
- return NULL;
-
- mutex_lock(&cpufreq_governor_mutex);
-
- t = find_governor(str_governor);
- }
- if (t && !try_module_get(t->owner))
- t = NULL;
-
- mutex_unlock(&cpufreq_governor_mutex);
+ if (request_module("cpufreq_%s", str_governor))
+ return NULL;
- return t;
+ return get_governor(str_governor);
}
/**
@@ -810,12 +814,14 @@ static ssize_t show_scaling_available_governors(struct cpufreq_policy *policy,
goto out;
}
+ mutex_lock(&cpufreq_governor_mutex);
for_each_governor(t) {
if (i >= (ssize_t) ((PAGE_SIZE / sizeof(char))
- (CPUFREQ_NAME_LEN + 2)))
- goto out;
+ break;
i += scnprintf(&buf[i], CPUFREQ_NAME_PLEN, "%s ", t->name);
}
+ mutex_unlock(&cpufreq_governor_mutex);
out:
i += sprintf(&buf[i], "\n");
return i;
@@ -1053,15 +1059,17 @@ static int cpufreq_init_policy(struct cpufreq_policy *policy)
struct cpufreq_governor *def_gov = cpufreq_default_governor();
struct cpufreq_governor *gov = NULL;
unsigned int pol = CPUFREQ_POLICY_UNKNOWN;
+ int ret;
if (has_target()) {
/* Update policy governor to the one used before hotplug. */
- gov = find_governor(policy->last_governor);
+ gov = get_governor(policy->last_governor);
if (gov) {
pr_debug("Restoring governor %s for cpu %d\n",
policy->governor->name, policy->cpu);
} else if (def_gov) {
gov = def_gov;
+ __module_get(gov->owner);
} else {
return -ENODATA;
}
@@ -1084,7 +1092,11 @@ static int cpufreq_init_policy(struct cpufreq_policy *policy)
return -ENODATA;
}
- return cpufreq_set_policy(policy, gov, pol);
+ ret = cpufreq_set_policy(policy, gov, pol);
+ if (gov)
+ module_put(gov->owner);
+
+ return ret;
}
static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy, unsigned int cpu)