linux-kernel - Re: [RFC PATCH 05/19] cpufreq: assert locking when accessing cpufreq_policy

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 12 Jan 2016 15:04:52 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Juri Lelli <juri.lelli@....com>
Cc:	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	peterz@...radead.org, rjw@...ysocki.net, mturquette@...libre.com,
	steve.muckle@...aro.org, vincent.guittot@...aro.org,
	morten.rasmussen@....com, dietmar.eggemann@....com
Subject: Re: [RFC PATCH 05/19] cpufreq: assert locking when accessing
 cpufreq_policy_list

On 11-01-16, 17:35, Juri Lelli wrote:
> cpufreq_policy_list is guarded by cpufreq_driver_lock. Add appropriate
> locking assertions to check that we always access the list while holding
> the associated lock.
> 
> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> Cc: Viresh Kumar <viresh.kumar@...aro.org>
> Signed-off-by: Juri Lelli <juri.lelli@....com>
> ---
>  drivers/cpufreq/cpufreq.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 00a00cd..63d6efb 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -65,6 +65,7 @@ static bool suitable_policy(struct cpufreq_policy *policy, bool active)
>  static struct cpufreq_policy *next_policy(struct cpufreq_policy *policy,
>  					  bool active)
>  {
> +	lockdep_assert_held(&cpufreq_driver_lock);
>  	do {
>  		policy = list_next_entry(policy, policy_list);
>  
> @@ -80,6 +81,7 @@ static struct cpufreq_policy *first_policy(bool active)
>  {
>  	struct cpufreq_policy *policy;
>  
> +	lockdep_assert_held(&cpufreq_driver_lock);

Because both first_policy() and next_policy() are parts of
for_each_suitable_policy() macro, checking this in first_policy() is
sufficient. next_policy() isn't designed to be used by any other code.

>  	/* No policies in the list */
>  	if (list_empty(&cpufreq_policy_list))
>  		return NULL;
> @@ -2430,6 +2432,7 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
>  	if (ret)
>  		goto err_boost_unreg;
>  
> +	lockdep_assert_held(&cpufreq_driver_lock);

Why do you need a cpufreq_driver_lock here? And the above change
should generate a lockdep here as the lock isn't taken right now.

>  	if (!(cpufreq_driver->flags & CPUFREQ_STICKY) &&
>  	    list_empty(&cpufreq_policy_list)) {
>  		/* if all ->init() calls failed, unregister */
> -- 
> 2.2.2

-- 
viresh