linux-kernel - [chanwoo:devfreq-testing 5/5] drivers/devfreq/governor_passive.c:190 cpufreq_passive_notifier_call() warn: variable dereferenced before check 'freqs' (see line 188)

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Message-ID: <202205060340.kwfOSVud-lkp@intel.com>
Date:   Fri, 6 May 2022 09:52:22 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     kbuild@...ts.01.org, Chanwoo Choi <cw00.choi@...sung.com>
Cc:     lkp@...el.com, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org
Subject: [chanwoo:devfreq-testing 5/5] drivers/devfreq/governor_passive.c:190
 cpufreq_passive_notifier_call() warn: variable dereferenced before check
 'freqs' (see line 188)

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/chanwoo/linux.git devfreq-testing
head:   f8605f8ed725beedd71e89872e49178b930250d4
commit: f8605f8ed725beedd71e89872e49178b930250d4 [5/5] PM / devfreq: Use cpufreq_policy instead of NR_CPU
config: i386-randconfig-m021 (https://download.01.org/0day-ci/archive/20220506/202205060340.kwfOSVud-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.2.0-20) 11.2.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@...el.com>
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>

New smatch warnings:
drivers/devfreq/governor_passive.c:190 cpufreq_passive_notifier_call() warn: variable dereferenced before check 'freqs' (see line 188)

Old smatch warnings:
drivers/devfreq/governor_passive.c:315 cpufreq_passive_register_notifier() warn: possible memory leak of 'parent_cpu_data'
drivers/devfreq/governor_passive.c:379 devfreq_passive_event_handler() warn: variable dereferenced before check 'p_data' (see line 376)

vim +/freqs +190 drivers/devfreq/governor_passive.c

009cb1af01de85 Saravana Kannan 2021-03-02  177  static int cpufreq_passive_notifier_call(struct notifier_block *nb,
009cb1af01de85 Saravana Kannan 2021-03-02  178  					 unsigned long event, void *ptr)
009cb1af01de85 Saravana Kannan 2021-03-02  179  {
f8605f8ed725be Chanwoo Choi    2022-04-27  180  	struct devfreq_passive_data *p_data =
009cb1af01de85 Saravana Kannan 2021-03-02  181  			container_of(nb, struct devfreq_passive_data, nb);
f8605f8ed725be Chanwoo Choi    2022-04-27  182  	struct devfreq *devfreq = (struct devfreq *)p_data->this;
009cb1af01de85 Saravana Kannan 2021-03-02  183  	struct devfreq_cpu_data *parent_cpu_data;
009cb1af01de85 Saravana Kannan 2021-03-02  184  	struct cpufreq_freqs *freqs = ptr;
009cb1af01de85 Saravana Kannan 2021-03-02  185  	unsigned int cur_freq;
009cb1af01de85 Saravana Kannan 2021-03-02  186  	int ret;
009cb1af01de85 Saravana Kannan 2021-03-02  187  
f8605f8ed725be Chanwoo Choi    2022-04-27 @188  	parent_cpu_data = get_parent_cpu_data(p_data, freqs->policy->cpu);
                                                                                                      ^^^^^^^^
Dereference

f8605f8ed725be Chanwoo Choi    2022-04-27  189  
f8605f8ed725be Chanwoo Choi    2022-04-27 @190  	if (event != CPUFREQ_POSTCHANGE || !freqs || !parent_cpu_data)
                                                                                           ^^^^^^
Check too late

009cb1af01de85 Saravana Kannan 2021-03-02  191  		return 0;
009cb1af01de85 Saravana Kannan 2021-03-02  192  
009cb1af01de85 Saravana Kannan 2021-03-02  193  	if (parent_cpu_data->cur_freq == freqs->new)
009cb1af01de85 Saravana Kannan 2021-03-02  194  		return 0;
009cb1af01de85 Saravana Kannan 2021-03-02  195  
009cb1af01de85 Saravana Kannan 2021-03-02  196  	cur_freq = parent_cpu_data->cur_freq;
009cb1af01de85 Saravana Kannan 2021-03-02  197  	parent_cpu_data->cur_freq = freqs->new;
009cb1af01de85 Saravana Kannan 2021-03-02  198  
009cb1af01de85 Saravana Kannan 2021-03-02  199  	mutex_lock(&devfreq->lock);
009cb1af01de85 Saravana Kannan 2021-03-02  200  	ret = devfreq_update_target(devfreq, freqs->new);
009cb1af01de85 Saravana Kannan 2021-03-02  201  	mutex_unlock(&devfreq->lock);
009cb1af01de85 Saravana Kannan 2021-03-02  202  	if (ret) {
009cb1af01de85 Saravana Kannan 2021-03-02  203  		parent_cpu_data->cur_freq = cur_freq;
009cb1af01de85 Saravana Kannan 2021-03-02  204  		dev_err(&devfreq->dev, "failed to update the frequency.\n");
009cb1af01de85 Saravana Kannan 2021-03-02  205  		return ret;
009cb1af01de85 Saravana Kannan 2021-03-02  206  	}
009cb1af01de85 Saravana Kannan 2021-03-02  207  
009cb1af01de85 Saravana Kannan 2021-03-02  208  	return 0;
009cb1af01de85 Saravana Kannan 2021-03-02  209  }

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