linux-kernel - Re: [PATCH] cpufreq: Init completion before kobject_init_and

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Date:   Mon, 14 Nov 2022 08:53:01 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Yongqiang Liu <liuyongqiang13@...wei.com>
Cc:     rafael@...nel.org, tobin@...nel.org, zhangxiaoxu5@...wei.com,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpufreq: Init completion before kobject_init_and_add()

On 10-11-22, 14:23, Yongqiang Liu wrote:
> In cpufreq_policy_alloc(), it will call uninitialed completion in
> cpufreq_sysfs_release() when kobject_init_and_add() fails. And
> that will cause a crash such as the following page fault in complete:
> 
> BUG: unable to handle page fault for address: fffffffffffffff8
> [..]
> RIP: 0010:complete+0x98/0x1f0
> [..]
> Call Trace:
>  kobject_put+0x1be/0x4c0
>  cpufreq_online.cold+0xee/0x1fd
>  cpufreq_add_dev+0x183/0x1e0
>  subsys_interface_register+0x3f5/0x4e0
>  cpufreq_register_driver+0x3b7/0x670
>  acpi_cpufreq_init+0x56c/0x1000 [acpi_cpufreq]
>  do_one_initcall+0x13d/0x780
>  do_init_module+0x1c3/0x630
>  load_module+0x6e67/0x73b0
>  __do_sys_finit_module+0x181/0x240
>  do_syscall_64+0x35/0x80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> Fixes: 4ebe36c94aed ("cpufreq: Fix kobject memleak")
> Signed-off-by: Yongqiang Liu <liuyongqiang13@...wei.com>
> ---
>  drivers/cpufreq/cpufreq.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 69b3d61852ac..7e56a42750ea 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1207,6 +1207,7 @@ static struct cpufreq_policy *cpufreq_policy_alloc(unsigned int cpu)
>  	if (!zalloc_cpumask_var(&policy->real_cpus, GFP_KERNEL))
>  		goto err_free_rcpumask;
>  
> +	init_completion(&policy->kobj_unregister);
>  	ret = kobject_init_and_add(&policy->kobj, &ktype_cpufreq,
>  				   cpufreq_global_kobject, "policy%u", cpu);
>  	if (ret) {
> @@ -1245,7 +1246,6 @@ static struct cpufreq_policy *cpufreq_policy_alloc(unsigned int cpu)
>  	init_rwsem(&policy->rwsem);
>  	spin_lock_init(&policy->transition_lock);
>  	init_waitqueue_head(&policy->transition_wait);
> -	init_completion(&policy->kobj_unregister);
>  	INIT_WORK(&policy->update, handle_update);
>  
>  	policy->cpu = cpu;

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh