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genirq: Fix race in register_irq_proc()

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Per-IRQ directories in procfs are created only when a handler is first
added to the irqdesc, not when the irqdesc is created.  In the case of
a shared IRQ, multiple tasks can race to create a directory.  This
race condition seems to have been present forever, but is easier to
hit with async probing.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Link: http://lkml.kernel.org/r/1443266636.2004.2.camel@decadent.org.uk
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
This commit is contained in:
Ben Hutchings 2015-09-26 12:23:56 +01:00 committed by Thomas Gleixner
parent d32dc9aa10
commit 95c2b17534
1 changed files with 17 additions and 2 deletions
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19
kernel/irq/proc.c
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@ -12,6 +12,7 @@
#include <linux/seq_file.h> #include <linux/seq_file.h>
#include <linux/interrupt.h> #include <linux/interrupt.h>
#include <linux/kernel_stat.h> #include <linux/kernel_stat.h>
#include <linux/mutex.h>
#include "internals.h" #include "internals.h"
@ -323,18 +324,29 @@ void register_handler_proc(unsigned int irq, struct irqaction *action)
void register_irq_proc(unsigned int irq, struct irq_desc *desc) void register_irq_proc(unsigned int irq, struct irq_desc *desc)
{ {
static DEFINE_MUTEX(register_lock);
char name [MAX_NAMELEN]; char name [MAX_NAMELEN];
if (!root_irq_dir || (desc->irq_data.chip == &no_irq_chip) || desc->dir) if (!root_irq_dir || (desc->irq_data.chip == &no_irq_chip))
return; return;
/*
* irq directories are registered only when a handler is
* added, not when the descriptor is created, so multiple
* tasks might try to register at the same time.
*/
mutex_lock(&register_lock);
if (desc->dir)
goto out_unlock;
memset(name, 0, MAX_NAMELEN); memset(name, 0, MAX_NAMELEN);
sprintf(name, "%d", irq); sprintf(name, "%d", irq);
/* create /proc/irq/1234 */ /* create /proc/irq/1234 */
desc->dir = proc_mkdir(name, root_irq_dir); desc->dir = proc_mkdir(name, root_irq_dir);
if (!desc->dir) if (!desc->dir)
return; goto out_unlock;
#ifdef CONFIG_SMP #ifdef CONFIG_SMP
/* create /proc/irq/<irq>/smp_affinity */ /* create /proc/irq/<irq>/smp_affinity */
@ -355,6 +367,9 @@ void register_irq_proc(unsigned int irq, struct irq_desc *desc)
proc_create_data("spurious", 0444, desc->dir, proc_create_data("spurious", 0444, desc->dir,
&irq_spurious_proc_fops, (void *)(long)irq); &irq_spurious_proc_fops, (void *)(long)irq);
out_unlock:
mutex_unlock(&register_lock);
} }
void unregister_irq_proc(unsigned int irq, struct irq_desc *desc) void unregister_irq_proc(unsigned int irq, struct irq_desc *desc)