Patch "genirq: Fix race in register_irq_proc()" has been added to the 3.10-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    genirq: Fix race in register_irq_proc()

to the 3.10-stable tree which can be found at:
    
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     genirq-fix-race-in-register_irq_proc.patch
and it can be found in the queue-3.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 95c2b17534654829db428f11bcf4297c059a2a7e Mon Sep 17 00:00:00 2001
From: Ben Hutchings <b...@decadent.org.uk>
Date: Sat, 26 Sep 2015 12:23:56 +0100
Subject: genirq: Fix race in register_irq_proc()

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

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 <b...@decadent.org.uk>
Link: http://lkml.kernel.org/r/1443266636.2004.2.ca...@decadent.org.uk
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 kernel/irq/proc.c |   19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

--- 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"
 
@@ -309,18 +310,29 @@ void register_handler_proc(unsigned int
 
 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 */
@@ -341,6 +353,9 @@ void register_irq_proc(unsigned int irq,
 
        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)


Patches currently in stable-queue which might be from b...@decadent.org.uk are

queue-3.10/genirq-fix-race-in-register_irq_proc.patch
queue-3.10/bonding-correct-the-mac-address-for-follow-fail_over_mac-policy.patch
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