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

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Date:   Wed, 30 Nov 2022 19:38:18 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>,
        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 Mon, Nov 14, 2022 at 4:23 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> 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>

Applied as 6.2 material, thanks!