linux-kernel - Re: [PATCH v1] cpufreq: scmi: Fix null-ptr-deref in scmi_cpufreq_get

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Message-ID: <20250408055505.oked4a3drsym46wz@vireshk-i7>
Date: Tue, 8 Apr 2025 11:25:05 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: Sudeep Holla <sudeep.holla@....com>
Cc: Henry Martin <bsdhenrymartin@...il.com>, cristian.marussi@....com,
	rafael@...nel.org, arm-scmi@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] cpufreq: scmi: Fix null-ptr-deref in
 scmi_cpufreq_get_rate()

On 07-04-25, 12:30, Sudeep Holla wrote:
> On Sat, Apr 05, 2025 at 01:54:47PM +0800, Henry Martin wrote:
> > cpufreq_cpu_get_raw() can return NULL when the target CPU is not present
> > in the policy->cpus mask. scmi_cpufreq_get_rate() does not check for
> > this case, which results in a NULL pointer dereference.
> > 
> > Add NULL check after cpufreq_cpu_get_raw() to prevent this issue.
> > 
> > Fixes: 99d6bdf33877 ("cpufreq: add support for CPU DVFS based on SCMI message protocol")
> > Signed-off-by: Henry Martin <bsdhenrymartin@...il.com>
> > ---
> >  drivers/cpufreq/scmi-cpufreq.c | 10 ++++++++--
> >  1 file changed, 8 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/cpufreq/scmi-cpufreq.c b/drivers/cpufreq/scmi-cpufreq.c
> > index c310aeebc8f3..c735f39245bf 100644
> > --- a/drivers/cpufreq/scmi-cpufreq.c
> > +++ b/drivers/cpufreq/scmi-cpufreq.c
> > @@ -37,11 +37,17 @@ static struct cpufreq_driver scmi_cpufreq_driver;
> >  
> >  static unsigned int scmi_cpufreq_get_rate(unsigned int cpu)
> >  {
> > -	struct cpufreq_policy *policy = cpufreq_cpu_get_raw(cpu);
> > -	struct scmi_data *priv = policy->driver_data;
> > +	struct cpufreq_policy *policy;
> > +	struct scmi_data *priv;
> >  	unsigned long rate;
> >  	int ret;
> >  
> > +	policy = cpufreq_cpu_get_raw(cpu);
> > +	if (!policy)
> 
> How about `if (unlikely(!policy))` instead ?

Henry, this change applies to all the patches you have sent. Also please send
them as a single series, as they are related changes.

-- 
viresh