Re: [PATCH v6] cpufreq/pasemi: fix an use-after-free inpas_cpufreq_cpu_init()

[wen.yang99 at zte.com.cn]

> > The cpu variable is still being used in the of_get_property() call
> > after the of_node_put() call, which may result in use-after-free.
> >
> > Fixes: a9acc26b75f6 ("cpufreq/pasemi: fix possible object reference leak")
> > Signed-off-by: Wen Yang <wen.yang99 at zte.com.cn>
> > Cc: "Rafael J. Wysocki" <rjw at rjwysocki.net>
> > Cc: Viresh Kumar <viresh.kumar at linaro.org>
> > Cc: Michael Ellerman <mpe at ellerman.id.au>
> > Cc: linuxppc-dev at lists.ozlabs.org
> > Cc: linux-pm at vger.kernel.org
> > Cc: linux-kernel at vger.kernel.org
> > ---
> > v6: keep the blank line and fix warning: label 'out_unmap_sdcpwr' defined but not used.
> > v5: put together the code to get, use, and release cpu device_node.
> > v4: restore the blank line.
> > v3: fix a leaked reference.
> > v2: clean up the code according to the advice of viresh.
> >
> >  drivers/cpufreq/pasemi-cpufreq.c | 26 ++++++++++++++------------
> >  1 file changed, 14 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/cpufreq/pasemi-cpufreq.c b/drivers/cpufreq/pasemi-cpufreq.c
> > index 6b1e4ab..7d557f9 100644
> > --- a/drivers/cpufreq/pasemi-cpufreq.c
> > +++ b/drivers/cpufreq/pasemi-cpufreq.c
> > @@ -131,10 +131,18 @@ static int pas_cpufreq_cpu_init(struct cpufreq_policy *policy)
> >      int err = -ENODEV;
> >
> >      cpu = of_get_cpu_node(policy->cpu, NULL);
> > +    if (!cpu)
> > +        goto out;
> >
> > +    max_freqp = of_get_property(cpu, "clock-frequency", NULL);
> >      of_node_put(cpu);
> > -    if (!cpu)
> > +    if (!max_freqp) {
> > +        err = -EINVAL;
> >          goto out;
> > +    }
> > +
> > +    /* we need the freq in kHz */
> > +    max_freq = *max_freqp / 1000;
> >
> >      dn = of_find_compatible_node(NULL, NULL, "1682m-sdc");
> >      if (!dn)
> > @@ -171,16 +179,6 @@ static int pas_cpufreq_cpu_init(struct cpufreq_policy *policy)
> >      }
> >
> >      pr_debug("init cpufreq on CPU %d\n", policy->cpu);
> > -
> > -    max_freqp = of_get_property(cpu, "clock-frequency", NULL);
> > -    if (!max_freqp) {
> > -        err = -EINVAL;
> > -        goto out_unmap_sdcpwr;
> > -    }
> > -
> > -    /* we need the freq in kHz */
> > -    max_freq = *max_freqp / 1000;
> > -
> >      pr_debug("max clock-frequency is at %u kHz\n", max_freq);
> >      pr_debug("initializing frequency table\n");
> >
> > @@ -196,7 +194,11 @@ static int pas_cpufreq_cpu_init(struct cpufreq_policy *policy)
> >      policy->cur = pas_freqs[cur_astate].frequency;
> >      ppc_proc_freq = policy->cur * 1000ul;
> >
> > -    return cpufreq_generic_init(policy, pas_freqs, get_gizmo_latency());
> > +    err = cpufreq_generic_init(policy, pas_freqs, get_gizmo_latency());
> 
> So you are trying to fix an earlier issue here with this. Should have
> been a separate patch. Over that I have just sent a patch now to make
> this routine return void.
> 
> https://lore.kernel.org/lkml/ee8cf5fb4b4a01fdf9199037ff6d835b935cfd13.1562902877.git.viresh.kumar@linaro.org/
> 
> So all you need to do is to remove the label out_unmap_sdcpwr instead.

Ok, thanks.

--
Cheers,
Wen