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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: Alexander Gordeev <lasaine@lvk.cs.msu.su>
Cc: Rodolfo Giometti <giometti@linux.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alexander Gordeev 2011-01-12 17:00:53 -08:00 committed by Linus Torvalds
parent 083e58666f
commit 2a5cd6e2fb
1 changed files with 11 additions and 8 deletions
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19
drivers/pps/pps.c
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@ -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 @@ int pps_register_cdev(struct pps_device *pps)
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;
}