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linux/kernel/irq/internals.h
Thomas Gleixner c291ee6221 genirq: Prevent proc race against freeing of irq descriptors 
Since the rework of the sparse interrupt code to actually free the
unused interrupt descriptors there exists a race between the /proc
interfaces to the irq subsystem and the code which frees the interrupt
descriptor.

CPU0				CPU1
				show_interrupts()
				  desc = irq_to_desc(X);
free_desc(desc)
  remove_from_radix_tree();
  kfree(desc);
				  raw_spinlock_irq(&desc->lock);

/proc/interrupts is the only interface which can actively corrupt
kernel memory via the lock access. /proc/stat can only read from freed
memory. Extremly hard to trigger, but possible.

The interfaces in /proc/irq/N/ are not affected by this because the
removal of the proc file is serialized in procfs against concurrent
readers/writers. The removal happens before the descriptor is freed.

For architectures which have CONFIG_SPARSE_IRQ=n this is a non issue
as the descriptor is never freed. It's merely cleared out with the irq
descriptor lock held. So any concurrent proc access will either see
the old correct value or the cleared out ones.

Protect the lookup and access to the irq descriptor in
show_interrupts() with the sparse_irq_lock.

Provide kstat_irqs_usr() which is protecting the lookup and access
with sparse_irq_lock and switch /proc/stat to use it.

Document the existing kstat_irqs interfaces so it's clear that the
caller needs to take care about protection. The users of these
interfaces are either not affected due to SPARSE_IRQ=n or already
protected against removal.

Fixes: 1f5a5b87f7 "genirq: Implement a sane sparse_irq allocator"
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
2014-12-13 13:33:07 +01:00

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/*
* IRQ subsystem internal functions and variables:
*
* Do not ever include this file from anything else than
* kernel/irq/. Do not even think about using any information outside
* of this file for your non core code.
*/
#include <linux/irqdesc.h>
#include <linux/kernel_stat.h>
#ifdef CONFIG_SPARSE_IRQ
# define IRQ_BITMAP_BITS (NR_IRQS + 8196)
#else
# define IRQ_BITMAP_BITS NR_IRQS
#endif
#define istate core_internal_state__do_not_mess_with_it
extern bool noirqdebug;
/*
* Bits used by threaded handlers:
* IRQTF_RUNTHREAD - signals that the interrupt handler thread should run
* IRQTF_WARNED - warning "IRQ_WAKE_THREAD w/o thread_fn" has been printed
* IRQTF_AFFINITY - irq thread is requested to adjust affinity
* IRQTF_FORCED_THREAD - irq action is force threaded
*/
enum {
IRQTF_RUNTHREAD,
IRQTF_WARNED,
IRQTF_AFFINITY,
IRQTF_FORCED_THREAD,
};
/*
* Bit masks for desc->core_internal_state__do_not_mess_with_it
*
* IRQS_AUTODETECT - autodetection in progress
* IRQS_SPURIOUS_DISABLED - was disabled due to spurious interrupt
* detection
* IRQS_POLL_INPROGRESS - polling in progress
* IRQS_ONESHOT - irq is not unmasked in primary handler
* IRQS_REPLAY - irq is replayed
* IRQS_WAITING - irq is waiting
* IRQS_PENDING - irq is pending and replayed later
* IRQS_SUSPENDED - irq is suspended
*/
enum {
IRQS_AUTODETECT = 0x00000001,
IRQS_SPURIOUS_DISABLED = 0x00000002,
IRQS_POLL_INPROGRESS = 0x00000008,
IRQS_ONESHOT = 0x00000020,
IRQS_REPLAY = 0x00000040,
IRQS_WAITING = 0x00000080,
IRQS_PENDING = 0x00000200,
IRQS_SUSPENDED = 0x00000800,
};
#include "debug.h"
#include "settings.h"
#define irq_data_to_desc(data) container_of(data, struct irq_desc, irq_data)
extern int __irq_set_trigger(struct irq_desc *desc, unsigned int irq,
unsigned long flags);
extern void __disable_irq(struct irq_desc *desc, unsigned int irq);
extern void __enable_irq(struct irq_desc *desc, unsigned int irq);
extern int irq_startup(struct irq_desc *desc, bool resend);
extern void irq_shutdown(struct irq_desc *desc);
extern void irq_enable(struct irq_desc *desc);
extern void irq_disable(struct irq_desc *desc);
extern void irq_percpu_enable(struct irq_desc *desc, unsigned int cpu);
extern void irq_percpu_disable(struct irq_desc *desc, unsigned int cpu);
extern void mask_irq(struct irq_desc *desc);
extern void unmask_irq(struct irq_desc *desc);
extern void unmask_threaded_irq(struct irq_desc *desc);
#ifdef CONFIG_SPARSE_IRQ
static inline void irq_mark_irq(unsigned int irq) { }
extern void irq_lock_sparse(void);
extern void irq_unlock_sparse(void);
#else
extern void irq_mark_irq(unsigned int irq);
static inline void irq_lock_sparse(void) { }
static inline void irq_unlock_sparse(void) { }
#endif
extern void init_kstat_irqs(struct irq_desc *desc, int node, int nr);
irqreturn_t handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action);
irqreturn_t handle_irq_event(struct irq_desc *desc);
/* Resending of interrupts :*/
void check_irq_resend(struct irq_desc *desc, unsigned int irq);
bool irq_wait_for_poll(struct irq_desc *desc);
void __irq_wake_thread(struct irq_desc *desc, struct irqaction *action);
#ifdef CONFIG_PROC_FS
extern void register_irq_proc(unsigned int irq, struct irq_desc *desc);
extern void unregister_irq_proc(unsigned int irq, struct irq_desc *desc);
extern void register_handler_proc(unsigned int irq, struct irqaction *action);
extern void unregister_handler_proc(unsigned int irq, struct irqaction *action);
#else
static inline void register_irq_proc(unsigned int irq, struct irq_desc *desc) { }
static inline void unregister_irq_proc(unsigned int irq, struct irq_desc *desc) { }
static inline void register_handler_proc(unsigned int irq,
struct irqaction *action) { }
static inline void unregister_handler_proc(unsigned int irq,
struct irqaction *action) { }
#endif
extern int irq_select_affinity_usr(unsigned int irq, struct cpumask *mask);
extern void irq_set_thread_affinity(struct irq_desc *desc);
extern int irq_do_set_affinity(struct irq_data *data,
const struct cpumask *dest, bool force);
/* Inline functions for support of irq chips on slow busses */
static inline void chip_bus_lock(struct irq_desc *desc)
{
if (unlikely(desc->irq_data.chip->irq_bus_lock))
desc->irq_data.chip->irq_bus_lock(&desc->irq_data);
}
static inline void chip_bus_sync_unlock(struct irq_desc *desc)
{
if (unlikely(desc->irq_data.chip->irq_bus_sync_unlock))
desc->irq_data.chip->irq_bus_sync_unlock(&desc->irq_data);
}
#define _IRQ_DESC_CHECK (1 << 0)
#define _IRQ_DESC_PERCPU (1 << 1)
#define IRQ_GET_DESC_CHECK_GLOBAL (_IRQ_DESC_CHECK)
#define IRQ_GET_DESC_CHECK_PERCPU (_IRQ_DESC_CHECK | _IRQ_DESC_PERCPU)
struct irq_desc *
__irq_get_desc_lock(unsigned int irq, unsigned long *flags, bool bus,
unsigned int check);
void __irq_put_desc_unlock(struct irq_desc *desc, unsigned long flags, bool bus);
static inline struct irq_desc *
irq_get_desc_buslock(unsigned int irq, unsigned long *flags, unsigned int check)
{
return __irq_get_desc_lock(irq, flags, true, check);
}
static inline void
irq_put_desc_busunlock(struct irq_desc *desc, unsigned long flags)
{
__irq_put_desc_unlock(desc, flags, true);
}
static inline struct irq_desc *
irq_get_desc_lock(unsigned int irq, unsigned long *flags, unsigned int check)
{
return __irq_get_desc_lock(irq, flags, false, check);
}
static inline void
irq_put_desc_unlock(struct irq_desc *desc, unsigned long flags)
{
__irq_put_desc_unlock(desc, flags, false);
}
/*
* Manipulation functions for irq_data.state
*/
static inline void irqd_set_move_pending(struct irq_data *d)
{
d->state_use_accessors |= IRQD_SETAFFINITY_PENDING;
}
static inline void irqd_clr_move_pending(struct irq_data *d)
{
d->state_use_accessors &= ~IRQD_SETAFFINITY_PENDING;
}
static inline void irqd_clear(struct irq_data *d, unsigned int mask)
{
d->state_use_accessors &= ~mask;
}
static inline void irqd_set(struct irq_data *d, unsigned int mask)
{
d->state_use_accessors |= mask;
}
static inline bool irqd_has_set(struct irq_data *d, unsigned int mask)
{
return d->state_use_accessors & mask;
}
static inline void kstat_incr_irqs_this_cpu(unsigned int irq, struct irq_desc *desc)
{
__this_cpu_inc(*desc->kstat_irqs);
__this_cpu_inc(kstat.irqs_sum);
}
#ifdef CONFIG_PM_SLEEP
bool irq_pm_check_wakeup(struct irq_desc *desc);
void irq_pm_install_action(struct irq_desc *desc, struct irqaction *action);
void irq_pm_remove_action(struct irq_desc *desc, struct irqaction *action);
#else
static inline bool irq_pm_check_wakeup(struct irq_desc *desc) { return false; }
static inline void
irq_pm_install_action(struct irq_desc *desc, struct irqaction *action) { }
static inline void
irq_pm_remove_action(struct irq_desc *desc, struct irqaction *action) { }
#endif
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