Commit 2a5cd6e2 authored by Alexander Gordeev's avatar Alexander Gordeev Committed by Linus Torvalds
Browse files

pps: make idr lock a mutex and protect idr_pre_get 



Now pps_idr_lock is never used in interrupt context so we can replace
spin_lock_irq/spin_unlock_irq with plain spin_lock/spin_unlock. But
there is also a potential race condition when someone can steal an id
which was allocated by idr_pre_get before it is used. So convert spin
lock to mutex and protect the whole id generation process.

Signed-off-by: default avatarAlexander Gordeev <lasaine@lvk.cs.msu.su>
Cc: Rodolfo Giometti <giometti@linux.it>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 083e5866

drivers/pps/pps.c

+11 −8
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ 
#include <linux/sched.h>

#include <linux/uaccess.h>

#include <linux/idr.h>

#include <linux/mutex.h>

#include <linux/cdev.h>

#include <linux/poll.h>

#include <linux/pps_kernel.h>
@@ -39,7 +40,7 @@ 
static dev_t pps_devt;

static struct class *pps_class;



static DEFINE_SPINLOCK(pps_idr_lock);

static DEFINE_MUTEX(pps_idr_lock);

static DEFINE_IDR(pps_idr);



/*
@@ -239,9 +240,9 @@ static void pps_device_destruct(struct device *dev) 


	/* release id here to protect others from using it while it's

	 * still in use */

	spin_lock_irq(&pps_idr_lock);

	mutex_lock(&pps_idr_lock);

	idr_remove(&pps_idr, pps->id);

	spin_unlock_irq(&pps_idr_lock);

	mutex_unlock(&pps_idr_lock);



	kfree(dev);

	kfree(pps);
@@ -252,17 +253,19 @@ int pps_register_cdev(struct pps_device *pps) 
	int err;

	dev_t devt;



	mutex_lock(&pps_idr_lock);

	/* Get new ID for the new PPS source */

	if (idr_pre_get(&pps_idr, GFP_KERNEL) == 0)

	if (idr_pre_get(&pps_idr, GFP_KERNEL) == 0) {

		mutex_unlock(&pps_idr_lock);

		return -ENOMEM;

	}



	/* Now really allocate the PPS source.

	 * After idr_get_new() calling the new source will be freely available

	 * into the kernel.

	 */

	spin_lock_irq(&pps_idr_lock);

	err = idr_get_new(&pps_idr, pps, &pps->id);

	spin_unlock_irq(&pps_idr_lock);

	mutex_unlock(&pps_idr_lock);



	if (err < 0)

		return err;
@@ -302,9 +305,9 @@ del_cdev: 
	cdev_del(&pps->cdev);



free_idr:

	spin_lock_irq(&pps_idr_lock);

	mutex_lock(&pps_idr_lock);

	idr_remove(&pps_idr, pps->id);

	spin_unlock_irq(&pps_idr_lock);

	mutex_unlock(&pps_idr_lock);



	return err;

}

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