[PATCH 3.4 68/92] genirq: Fix race in register_irq_proc()

lizf
2016-04-18T10:50:50Z

From: Ben Hutchings <ben@decadent.org.uk>

3.4.112-rc1 review patch. If anyone has any objections, please let me know.

------------------

commit 95c2b17534654829db428f11bcf4297c059a2a7e upstream.

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>
Signed-off-by: Zefan Li <lizefan@huawei.com>
---
kernel/irq/proc.c | 19 +++++++++++++++++--
1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c
index fb655f5f..15374d0 100644
--- a/kernel/irq/proc.c
+++ b/kernel/irq/proc.c
@@ -12,6 +12,7 @@
#include <linux/seq_file.h>
#include <linux/interrupt.h>
#include <linux/kernel_stat.h>
+#include <linux/mutex.h>

#include "internals.h"

@@ -326,18 +327,29 @@ void register_handler_proc(unsigned int irq, struct irqaction *action)

void register_irq_proc(unsigned int irq, struct irq_desc *desc)
{
+ static DEFINE_MUTEX(register_lock);
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;

+ /*
+ * 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);
sprintf(name, "%d", irq);

/* create /proc/irq/1234 */
desc->dir = proc_mkdir(name, root_irq_dir);
if (!desc->dir)
- return;
+ goto out_unlock;

#ifdef CONFIG_SMP
/* create /proc/irq/<irq>/smp_affinity */
@@ -358,6 +370,9 @@ void register_irq_proc(unsigned int irq, struct irq_desc *desc)

proc_create_data("spurious", 0444, desc->dir,
&irq_spurious_proc_fops, (void *)(long)irq);
+
+out_unlock:
+ mutex_unlock(&register_lock);
}

void unregister_irq_proc(unsigned int irq, struct irq_desc *desc)
--
1.9.1