Re: [PATCH] cpuidle: change enter_s2idle() prototype

Rafael J. Wysocki
2020-06-29T16:45:25Z

On Monday, June 29, 2020 11:05:40 AM CEST Neal Liu wrote:
> Control Flow Integrity(CFI) is a security mechanism that disallows
> changes to the original control flow graph of a compiled binary,
> making it significantly harder to perform such attacks.
>
> init_state_node() assigns same function pointer to idle_state->enter
> and idle_state->enter_s2idle. This definitely causes CFI failure
> when calling either enter() or enter_s2idle().
>
> Align enter_s2idle() with enter() function prototype to fix CFI
> failure.

That needs to be documented somewhere close to the definition of the
callbacks in question.

Otherwise it is completely unclear why this is a good idea.

> Signed-off-by: Neal Liu <neal.liu@mediatek.com>
> ---
> drivers/acpi/processor_idle.c | 6 ++++--
> drivers/cpuidle/cpuidle-tegra.c | 8 +++++---
> drivers/idle/intel_idle.c | 6 ++++--
> include/linux/cpuidle.h | 6 +++---
> 4 files changed, 16 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index 75534c5..6ffb6c9 100644
> --- a/drivers/acpi/processor_idle.c
> +++ b/drivers/acpi/processor_idle.c
> @@ -655,8 +655,8 @@ static int acpi_idle_enter(struct cpuidle_device *dev,
> return index;
> }
>
> -static void acpi_idle_enter_s2idle(struct cpuidle_device *dev,
> - struct cpuidle_driver *drv, int index)
> +static int acpi_idle_enter_s2idle(struct cpuidle_device *dev,
> + struct cpuidle_driver *drv, int index)
> {
> struct acpi_processor_cx *cx = per_cpu(acpi_cstate[index], dev->cpu);
>
> @@ -674,6 +674,8 @@ static void acpi_idle_enter_s2idle(struct cpuidle_device *dev,
> }
> }
> acpi_idle_do_entry(cx);
> +
> + return 0;
> }
>
> static int acpi_processor_setup_cpuidle_cx(struct acpi_processor *pr,
> diff --git a/drivers/cpuidle/cpuidle-tegra.c b/drivers/cpuidle/cpuidle-tegra.c
> index 1500458..a12fb14 100644
> --- a/drivers/cpuidle/cpuidle-tegra.c
> +++ b/drivers/cpuidle/cpuidle-tegra.c
> @@ -253,11 +253,13 @@ static int tegra_cpuidle_enter(struct cpuidle_device *dev,
> return err ? -1 : index;
> }
>
> -static void tegra114_enter_s2idle(struct cpuidle_device *dev,
> - struct cpuidle_driver *drv,
> - int index)
> +static int tegra114_enter_s2idle(struct cpuidle_device *dev,
> + struct cpuidle_driver *drv,
> + int index)
> {
> tegra_cpuidle_enter(dev, drv, index);
> +
> + return 0;
> }
>
> /*
> diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
> index f449584..b178da3 100644
> --- a/drivers/idle/intel_idle.c
> +++ b/drivers/idle/intel_idle.c
> @@ -175,13 +175,15 @@ static __cpuidle int intel_idle(struct cpuidle_device *dev,
> * Invoked as a suspend-to-idle callback routine with frozen user space, frozen
> * scheduler tick and suspended scheduler clock on the target CPU.
> */
> -static __cpuidle void intel_idle_s2idle(struct cpuidle_device *dev,
> - struct cpuidle_driver *drv, int index)
> +static __cpuidle int intel_idle_s2idle(struct cpuidle_device *dev,
> + struct cpuidle_driver *drv, int index)
> {
> unsigned long eax = flg2MWAIT(drv->states[index].flags);
> unsigned long ecx = 1; /* break on interrupt flag */
>
> mwait_idle_with_hints(eax, ecx);
> +
> + return 0;
> }
>
> /*
> diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
> index ec2ef63..bee10c0 100644
> --- a/include/linux/cpuidle.h
> +++ b/include/linux/cpuidle.h
> @@ -66,9 +66,9 @@ struct cpuidle_state {
> * suspended, so it must not re-enable interrupts at any point (even
> * temporarily) or attempt to change states of clock event devices.
> */
> - void (*enter_s2idle) (struct cpuidle_device *dev,
> - struct cpuidle_driver *drv,
> - int index);
> + int (*enter_s2idle)(struct cpuidle_device *dev,
> + struct cpuidle_driver *drv,
> + int index);
> };
>
> /* Idle State Flags */
> --
> 1.7.9.5