Re: [PATCH] cpufreq: amd-pstate: avoid uninitialized variable use
From: Rafael J. Wysocki
Date: Thu Feb 09 2023 - 14:23:11 EST
On Thu, Feb 9, 2023 at 6:04 AM Huang Rui <ray.huang@xxxxxxx> wrote:
>
> On Wed, Feb 08, 2023 at 12:12:51AM +0800, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@xxxxxxxx>
> >
> > The new epp support causes warnings about three separate
> > but related bugs:
> >
> > 1) failing before allocation should just return an error:
> >
> > drivers/cpufreq/amd-pstate.c:951:6: error: variable 'ret' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
> > if (!dev)
> > ^~~~
> > drivers/cpufreq/amd-pstate.c:1018:9: note: uninitialized use occurs here
> > return ret;
> > ^~~
> >
> > 2) wrong variable to store return code:
> >
> > drivers/cpufreq/amd-pstate.c:963:6: error: variable 'ret' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
> > if (rc)
> > ^~
> > drivers/cpufreq/amd-pstate.c:1019:9: note: uninitialized use occurs here
> > return ret;
> > ^~~
> > drivers/cpufreq/amd-pstate.c:963:2: note: remove the 'if' if its condition is always false
> > if (rc)
> > ^~~~~~~
> >
> > 3) calling amd_pstate_set_epp() in cleanup path after determining
> > that it should not be called:
> >
> > drivers/cpufreq/amd-pstate.c:1055:6: error: variable 'epp' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
> > if (cpudata->epp_policy == cpudata->policy)
> > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > drivers/cpufreq/amd-pstate.c:1080:30: note: uninitialized use occurs here
> > amd_pstate_set_epp(cpudata, epp);
> > ^~~
> >
> > All three are trivial to fix, but most likely there are additional bugs
> > in this function when the error handling was not really tested.
> >
> > Fixes: ffa5096a7c33 ("cpufreq: amd-pstate: implement Pstate EPP support for the AMD processors")
> > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
>
> Thanks!
>
> Acked-by: Huang Rui <ray.huang@xxxxxxx>
>
> > ---
> > drivers/cpufreq/amd-pstate.c | 9 ++++-----
> > 1 file changed, 4 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> > index 168a28bed6ee..847f5f31396d 100644
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -940,7 +940,6 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
> > int min_freq, max_freq, nominal_freq, lowest_nonlinear_freq, ret;
> > struct amd_cpudata *cpudata;
> > struct device *dev;
> > - int rc;
> > u64 value;
> >
> > /*
> > @@ -950,7 +949,7 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
> > amd_perf_ctl_reset(policy->cpu);
> > dev = get_cpu_device(policy->cpu);
> > if (!dev)
> > - goto free_cpudata1;
> > + return -ENODEV;
> >
> > cpudata = kzalloc(sizeof(*cpudata), GFP_KERNEL);
> > if (!cpudata)
> > @@ -959,8 +958,8 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
> > cpudata->cpu = policy->cpu;
> > cpudata->epp_policy = 0;
> >
> > - rc = amd_pstate_init_perf(cpudata);
> > - if (rc)
> > + ret = amd_pstate_init_perf(cpudata);
> > + if (ret)
> > goto free_cpudata1;
> >
> > min_freq = amd_get_min_freq(cpudata);
> > @@ -1076,9 +1075,9 @@ static void amd_pstate_epp_init(unsigned int cpu)
> > value |= (u64)epp << 24;
> > }
> >
> > + amd_pstate_set_epp(cpudata, epp);
> > skip_epp:
> > WRITE_ONCE(cpudata->cppc_req_cached, value);
> > - amd_pstate_set_epp(cpudata, epp);
> > cpufreq_cpu_put(policy);
> > }
> >
> > --
Applied, thanks!