linux-kernel - Re: [PATCH RFC] PM: EM: Add to em_pd

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Message-ID: <CAJZ5v0hMSNfEVg-PUrzvPLO2oMFRJypgn26w7B8XqsD1_9KT4A@mail.gmail.com>
Date: Wed, 29 Oct 2025 13:40:29 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Lukasz Luba <lukasz.luba@....com>, Peng Fan <peng.fan@....com>
Cc: arm-scmi@...r.kernel.org, Sudeep Holla <sudeep.holla@....com>, 
	Pavel Machek <pavel@...nel.org>, Ulf Hansson <ulf.hansson@...aro.org>, 
	Cristian Marussi <cristian.marussi@....com>, "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, 
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Len Brown <lenb@...nel.org>, Changwoo Min <changwoo@...lia.com>
Subject: Re: [PATCH RFC] PM: EM: Add to em_pd_list only when no failure

On Wed, Oct 29, 2025 at 10:00 AM Lukasz Luba <lukasz.luba@....com> wrote:
>
>
>
> On 10/28/25 14:23, Peng Fan wrote:
> > When em_create_perf_table() returns failure, pd is freed, there dev->em_pd
> > is not valid. Then accessing dev->em_pd->node will trigger kernel panic
> > in em_dev_register_pd_no_update(). So return early if 'ret' is non-zero.
> >
> > Kernel dump:
> > cpu cpu0: EM: invalid power: 0
> > Unable to handle kernel NULL pointer dereference at virtual address
> > 0000000000000008
> > Mem abort info:
> > pc : em_dev_register_pd_no_update+0xb4/0x79c
> > lr : em_dev_register_pd_no_update+0x9c/0x79c
> > Call trace:
> >   em_dev_register_pd_no_update+0xb4/0x79c (P)
> >   em_dev_register_perf_domain+0x18/0x58
> >   scmi_cpufreq_register_em+0x84/0xb8
> >   cpufreq_online+0x48c/0xb74
> >   cpufreq_add_dev+0x80/0x98
> >   subsys_interface_register+0x100/0x11c
> >   cpufreq_register_driver+0x158/0x278
> >   scmi_cpufreq_probe+0x1f8/0x2e0
> >   scmi_dev_probe+0x28/0x3c
> >   really_probe+0xbc/0x29c
> >   __driver_probe_device+0x78/0x12c
> >   driver_probe_device+0x3c/0x15c
> >   __device_attach_driver+0xb8/0x134
> >   bus_for_each_drv+0x84/0xe4
> >
> > Fixes: cbe5aeedecc7 ("PM: EM: Assign a unique ID when creating a performance domain")
> > Signed-off-by: Peng Fan <peng.fan@....com>
> > ---
> >   kernel/power/energy_model.c | 5 ++++-
> >   1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
> > index e669d5057fca6da9612575a1c626474e60e7f7c4..11af9f64aa8276e47e0a5b2d615b227368af5480 100644
> > --- a/kernel/power/energy_model.c
> > +++ b/kernel/power/energy_model.c
> > @@ -693,13 +693,16 @@ int em_dev_register_pd_no_update(struct device *dev, unsigned int nr_states,
> >
> >   unlock:
> >       mutex_unlock(&em_pd_mutex);
> > +     if (ret)
> > +             return ret;
> >
> >       mutex_lock(&em_pd_list_mutex);
> >       list_add_tail(&dev->em_pd->node, &em_pd_list);
> >       mutex_unlock(&em_pd_list_mutex);
> >
> >       em_notify_pd_created(dev->em_pd);
> > -     return ret;
> > +
> > +     return 0;
> >   }
> >   EXPORT_SYMBOL_GPL(em_dev_register_pd_no_update);
> >
> >
> > ---
> > base-commit: f7d2388eeec24966fc4d5cf32d706f0514f29ac5
> > change-id: 20251028-fix-energy-6b63b72ae9c6
> >
> > Best regards,
>
>
> Thank you for the patch!
>
> Reviewed-by: Lukasz Luba <lukasz.luba@....com>

Applied, thanks!