Re: [patch 2/7] genirq: Add protection against unsafe usage of generic_handle_irq()

[Marc Zyngier <maz@kernel.org>]

On 2020-03-06 13:03, Thomas Gleixner wrote:
> In general calling generic_handle_irq() with interrupts disabled from 
> non
> interrupt context is harmless. For some interrupt controllers like the 
> x86
> trainwrecks this is outright dangerous as it might corrupt state if an
> interrupt affinity change is pending.
> 
> Add infrastructure which allows to mark interrupts as unsafe and catch 
> such
> usage in generic_handle_irq().
> 
> Reported-by: sathyanarayanan.kuppuswamy@linux.intel.com
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
>  include/linux/irq.h    |   13 +++++++++++++
>  kernel/irq/internals.h |    8 ++++++++
>  kernel/irq/irqdesc.c   |    6 ++++++
>  kernel/irq/resend.c    |    5 +++--
>  4 files changed, 30 insertions(+), 2 deletions(-)
> 
> --- a/include/linux/irq.h
> +++ b/include/linux/irq.h
> @@ -211,6 +211,8 @@ struct irq_data {
>   * IRQD_CAN_RESERVE		- Can use reservation mode
>   * IRQD_MSI_NOMASK_QUIRK	- Non-maskable MSI quirk for affinity change
>   *				  required
> + * IRQD_HANDLE_ENFORCE_IRQCTX	- Enforce that handle_irq_*() is only 
> invoked
> + *				  from actual interrupt context.
>   */
>  enum {
>  	IRQD_TRIGGER_MASK		= 0xf,
> @@ -234,6 +236,7 @@ enum {
>  	IRQD_DEFAULT_TRIGGER_SET	= (1 << 25),
>  	IRQD_CAN_RESERVE		= (1 << 26),
>  	IRQD_MSI_NOMASK_QUIRK		= (1 << 27),
> +	IRQD_HANDLE_ENFORCE_IRQCTX	= (1 << 28),
>  };
> 
>  #define __irqd_to_state(d) ACCESS_PRIVATE((d)->common, 
> state_use_accessors)
> @@ -303,6 +306,16 @@ static inline bool irqd_is_single_target
>  	return __irqd_to_state(d) & IRQD_SINGLE_TARGET;
>  }
> 
> +static inline void irqd_set_handle_enforce_irqctx(struct irq_data *d)
> +{
> +	__irqd_to_state(d) |= IRQD_HANDLE_ENFORCE_IRQCTX;
> +}
> +
> +static inline bool irqd_is_handle_enforce_irqctx(struct irq_data *d)
> +{
> +	return __irqd_to_state(d) & IRQD_HANDLE_ENFORCE_IRQCTX;
> +}
> +
>  static inline bool irqd_is_wakeup_set(struct irq_data *d)
>  {
>  	return __irqd_to_state(d) & IRQD_WAKEUP_STATE;
> --- a/kernel/irq/internals.h
> +++ b/kernel/irq/internals.h
> @@ -425,6 +425,10 @@ static inline struct cpumask *irq_desc_g
>  {
>  	return desc->pending_mask;
>  }
> +static inline bool handle_enforce_irqctx(struct irq_data *data)
> +{
> +	return irqd_is_handle_enforce_irqctx(data);
> +}
>  bool irq_fixup_move_pending(struct irq_desc *desc, bool force_clear);
>  #else /* CONFIG_GENERIC_PENDING_IRQ */
>  static inline bool irq_can_move_pcntxt(struct irq_data *data)
> @@ -451,6 +455,10 @@ static inline bool irq_fixup_move_pendin
>  {
>  	return false;
>  }
> +static inline bool handle_enforce_irqctx(struct irq_data *data)
> +{
> +	return false;
> +}
>  #endif /* !CONFIG_GENERIC_PENDING_IRQ */
> 
>  #if !defined(CONFIG_IRQ_DOMAIN) || 
> !defined(CONFIG_IRQ_DOMAIN_HIERARCHY)
> --- a/kernel/irq/irqdesc.c
> +++ b/kernel/irq/irqdesc.c
> @@ -638,9 +638,15 @@ void irq_init_desc(unsigned int irq)
>  int generic_handle_irq(unsigned int irq)
>  {
>  	struct irq_desc *desc = irq_to_desc(irq);
> +	struct irq_data *data;
> 
>  	if (!desc)
>  		return -EINVAL;
> +
> +	data = irq_desc_get_irq_data(desc);
> +	if (WARN_ON_ONCE(!in_irq() && handle_enforce_irqctx(data)))
> +		return -EPERM;

It is a bit sad that there are only *two* users in the tree that
actually check the return value of generic_handle_irq(). Thankfully,
the WARN_ON should wake people up.

> +
>  	generic_handle_irq_desc(desc);
>  	return 0;
>  }
> --- a/kernel/irq/resend.c
> +++ b/kernel/irq/resend.c
> @@ -72,8 +72,9 @@ void check_irq_resend(struct irq_desc *d
>  		desc->istate &= ~IRQS_PENDING;
>  		desc->istate |= IRQS_REPLAY;
> 
> -		if (!desc->irq_data.chip->irq_retrigger ||
> -		    !desc->irq_data.chip->irq_retrigger(&desc->irq_data)) {
> +		if ((!desc->irq_data.chip->irq_retrigger ||
> +		    !desc->irq_data.chip->irq_retrigger(&desc->irq_data)) &&
> +		    !handle_enforce_irqctx(&desc->irq_data)) {
>  #ifdef CONFIG_HARDIRQS_SW_RESEND
>  			unsigned int irq = irq_desc_get_irq(desc);

Acked-by: Marc Zyngier <maz@kernel.org>

         M.
-- 
Jazz is not dead. It just smells funny...