答复: [外部邮件] Re: [PATCH] cpufreq: acpi-cpufreq: add NULL check for acpi_perf_data before freeing

["Li,Rongqing" <lirongqing@baidu.com>]

> >
> > If alloc_percpu() fails in acpi_cpufreq_early_init(), acpi_perf_data
> > is NULL.  Calling free_acpi_perf_data() will execute per_cpu_ptr(NULL,
> > i), which does not return NULL but an offset pointer.
> 
> Hi RongQing,
> 
> Could you please confirm if acpi_perf_data() can ever be executed when
> alloc_percpu() fails?

You are right, acpi_perf_data() can not be called when alloc_percpu() fails

Please drop this patch

thanks 

[Li,Rongqing] 



> 
> 
> > Dereferencing ->shared_cpu_map on this invalid pointer leads to a kernel
> > crash.
> >
> > Fix these issues by adding a NULL check at the start of
> > free_acpi_perf_data() and setting acpi_perf_data to NULL after freeing.
> >
> > Signed-off-by: Li RongQing <lirongqing@baidu.com>
> > ---
> >   drivers/cpufreq/acpi-cpufreq.c | 5 ++++-
> >   1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
> > index 87e4923..cd2ca87 100644
> > --- a/drivers/cpufreq/acpi-cpufreq.c
> > +++ b/drivers/cpufreq/acpi-cpufreq.c
> > @@ -517,11 +517,14 @@ static void free_acpi_perf_data(void)
> >   {
> >   	unsigned int i;
> >
> > -	/* Freeing a NULL pointer is OK, and alloc_percpu zeroes. */
> > +	if (!acpi_perf_data)
> > +		return;
> > +
> >   	for_each_possible_cpu(i)
> >   		free_cpumask_var(per_cpu_ptr(acpi_perf_data, i)
> >   				 ->shared_cpu_map);
> >   	free_percpu(acpi_perf_data);
> > +	acpi_perf_data = NULL;
> >   }
> >
> >   static int cpufreq_boost_down_prep(unsigned int cpu)
> 
> 
> --
> Thx and BRs,
> Zhongqiu Han