linux-kernel - Re: [PATCH v2] ACPI: CPPC: Add NULL pointer check to cppc_get

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Date:   Wed, 24 Nov 2021 15:46:34 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux ACPI <linux-acpi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: Re: [PATCH v2] ACPI: CPPC: Add NULL pointer check to cppc_get_perf()

On Thu, Nov 18, 2021 at 9:37 PM Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Subject: [PATCH] ACPI: CPPC: Add NULL pointer check to cppc_get_perf()
>
> Check cpc_desc against NULL in cppc_get_perf(), so it doesn't crash
> down the road if cpc_desc is NULL.
>
> Fixes: 0654cf05d17b ("ACPI: CPPC: Introduce cppc_get_nominal_perf()")
> Reported-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Cc: 5.15+ <stable@...r.kernel.org> # 5.15+

Sorry for the late test, I bricked my previous ADL rig.
Tested-by: Kai-Heng Feng <kai.heng.feng@...onical.com>

> ---
>
> -> v2: Check cpc_desc against NULL before using it to initialize reg.
>
> ---
>  drivers/acpi/cppc_acpi.c |    9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> Index: linux-pm/drivers/acpi/cppc_acpi.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/cppc_acpi.c
> +++ linux-pm/drivers/acpi/cppc_acpi.c
> @@ -998,7 +998,14 @@ static int cpc_write(int cpu, struct cpc
>  static int cppc_get_perf(int cpunum, enum cppc_regs reg_idx, u64 *perf)
>  {
>         struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpunum);
> -       struct cpc_register_resource *reg = &cpc_desc->cpc_regs[reg_idx];
> +       struct cpc_register_resource *reg;
> +
> +       if (!cpc_desc) {
> +               pr_debug("No CPC descriptor for CPU:%d\n", cpunum);
> +               return -ENODEV;
> +       }
> +
> +       reg = &cpc_desc->cpc_regs[reg_idx];
>
>         if (CPC_IN_PCC(reg)) {
>                 int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpunum);
>
>
>