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Date: Wed, 20 Feb 2013 20:35:27 -0500
From: Peter Hurley <peter@...leysoftware.com>
To: George Spelvin <linux@...izon.com>
Cc: linux-serial@...r.kernel.org, gregkh@...uxfoundation.org,
linux-kernel@...r.kernel.org, giometti@...ux.it
Subject: Re: [PATCH v2 8/9] pps: Use a single cdev
On Tue, 2013-02-12 at 02:02 -0500, George Spelvin wrote:
> One per device just seems wasteful, when we already manintain a
> data structure to map minor numbers to devices, and we already have
> a PPS_MAX_SOURCES #define.
>
> This is also a more comprehensive fix to the use-after-free bug
> that has already received a minimal patch.
> ---
> drivers/pps/pps.c | 66 ++++++++++++++++++++++++----------------------
> include/linux/pps_kernel.h | 1 -
> 2 files changed, 34 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
> index 6437703..754b0b5 100644
> --- a/drivers/pps/pps.c
> +++ b/drivers/pps/pps.c
> @@ -41,6 +41,8 @@
>
> static dev_t pps_devt;
> static struct class *pps_class;
> +static struct cdev pps_cdev;
> +
>
> static DEFINE_MUTEX(pps_idr_lock);
> static DEFINE_IDR(pps_idr);
> @@ -244,17 +246,23 @@ static long pps_cdev_ioctl(struct file *file,
>
> static int pps_cdev_open(struct inode *inode, struct file *file)
> {
> - struct pps_device *pps = container_of(inode->i_cdev,
> - struct pps_device, cdev);
> - file->private_data = pps;
> - kobject_get(&pps->dev->kobj);
> - return 0;
> + int err = -ENXIO;
> + struct pps_device *pps;
> +
> + rcu_read_lock();
> + pps = idr_find(&pps_idr, iminor(inode));
> + if (pps) {
> + file->private_data = pps;
> + kobject_get(&pps->dev->kobj);
> + err = 0;
> + }
> + rcu_read_unlock();
This should be:
rcu_read_lock();
pps = idr_find(&pps_idr, iminor(inode));
rcu_read_unlock();
if (pps) {
file->private_data = pps;
kobject_get(&pps->dev->kobj);
err = 0;
}
It's only the internal structures of idr that need rcu barriers.
> + return err;
> }
>
> static int pps_cdev_release(struct inode *inode, struct file *file)
> {
> - struct pps_device *pps = container_of(inode->i_cdev,
> - struct pps_device, cdev);
> + struct pps_device *pps = file->private_data;
> kobject_put(&pps->dev->kobj);
> return 0;
> }
> @@ -277,8 +285,6 @@ static void pps_device_destruct(struct device *dev)
> {
> struct pps_device *pps = dev_get_drvdata(dev);
>
> - cdev_del(&pps->cdev);
> -
> /* Now we can release the ID for re-use */
> pr_debug("deallocating pps%d\n", pps->id);
> mutex_lock(&pps_idr_lock);
> @@ -295,17 +301,14 @@ int pps_register_cdev(struct pps_device *pps)
> 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) {
> - mutex_unlock(&pps_idr_lock);
> - return -ENOMEM;
> - }
> -
> - /* Now really allocate the PPS source.
> + /* Get new ID for the new PPS source.
> * After idr_get_new() calling the new source will be freely available
> * into the kernel.
> */
> - err = idr_get_new(&pps_idr, pps, &pps->id);
> + if (idr_pre_get(&pps_idr, GFP_KERNEL) == 0)
> + err = -ENOMEM;
> + else
> + err = idr_get_new(&pps_idr, pps, &pps->id);
Your maintainer should be letting you know about this:
-------- Forwarded Message --------
From: Tejun Heo <tj@...nel.org>
To: akpm@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org, rusty@...tcorp.com.au, bfields@...ldses.org,
skinsbursky@...allels.com, ebiederm@...ssion.com, jmorris@...ei.org, axboe@...nel.dk,
Tejun Heo <tj@...nel.org>, Rodolfo Giometti <giometti@...eenne.com>
Subject: [PATCH 41/62] pps: convert to idr_alloc()
Date: Sat, 2 Feb 2013 17:20:42 -0800
Convert to the much saner new idr interface.
Only compile tested.
Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: Rodolfo Giometti <giometti@...eenne.com>
---
This patch depends on an earlier idr changes and I think it would be
best to route these together through -mm. Please holler if there's
any objection. Thanks.
drivers/pps/kapi.c | 2 +-
drivers/pps/pps.c | 36 ++++++++++++++----------------------
2 files changed, 15 insertions(+), 23 deletions(-)
diff --git a/drivers/pps/kapi.c b/drivers/pps/kapi.c
index f197e8e..cdad4d9 100644
--- a/drivers/pps/kapi.c
+++ b/drivers/pps/kapi.c
@@ -102,7 +102,7 @@ struct pps_device *pps_register_source(struct pps_source_info *info,
goto pps_register_source_exit;
}
- /* These initializations must be done before calling idr_get_new()
+ /* These initializations must be done before calling idr_alloc()
* in order to avoid reces into pps_event().
*/
pps->params.api_version = PPS_API_VERS;
diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
index 2420d5a..de8e663 100644
--- a/drivers/pps/pps.c
+++ b/drivers/pps/pps.c
@@ -290,29 +290,21 @@ int pps_register_cdev(struct pps_device *pps)
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) {
- 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.
+ /*
+ * Get new ID for the new PPS source. After idr_alloc() calling
+ * the new source will be freely available into the kernel.
*/
- err = idr_get_new(&pps_idr, pps, &pps->id);
- mutex_unlock(&pps_idr_lock);
-
- if (err < 0)
- return err;
-
- pps->id &= MAX_IDR_MASK;
- if (pps->id >= PPS_MAX_SOURCES) {
- pr_err("%s: too many PPS sources in the system\n",
- pps->info.name);
- err = -EBUSY;
- goto free_idr;
+ err = idr_alloc(&pps_idr, pps, 0, PPS_MAX_SOURCES, GFP_KERNEL);
+ if (err < 0) {
+ if (err == -ENOSPC) {
+ pr_err("%s: too many PPS sources in the system\n",
+ pps->info.name);
+ err = -EBUSY;
+ }
+ goto out_unlock;
}
+ pps->id = err;
+ mutex_unlock(&pps_idr_lock);
devt = MKDEV(MAJOR(pps_devt), pps->id);
@@ -345,8 +337,8 @@ del_cdev:
free_idr:
mutex_lock(&pps_idr_lock);
idr_remove(&pps_idr, pps->id);
+out_unlock:
mutex_unlock(&pps_idr_lock);
-
return err;
}
--
1.8.1
> mutex_unlock(&pps_idr_lock);
>
> if (err < 0)
> @@ -321,33 +324,21 @@ int pps_register_cdev(struct pps_device *pps)
>
> devt = MKDEV(MAJOR(pps_devt), pps->id);
>
> - cdev_init(&pps->cdev, &pps_cdev_fops);
> - pps->cdev.owner = pps->info.owner;
> -
> - err = cdev_add(&pps->cdev, devt, 1);
> - if (err) {
> - pr_err("%s: failed to add char device %d:%d\n",
> - pps->info.name, MAJOR(pps_devt), pps->id);
> - goto free_idr;
> - }
> pps->dev = device_create(pps_class, pps->info.dev, devt, pps,
> "pps%d", pps->id);
> if (IS_ERR(pps->dev)) {
> err = PTR_ERR(pps->dev);
> - goto del_cdev;
> + goto free_idr;
> }
>
> /* Override the release function with our own */
> pps->dev->release = pps_device_destruct;
>
> pr_debug("source %s got cdev (%d:%d)\n", pps->info.name,
> - MAJOR(pps_devt), pps->id);
> + MAJOR(devt), MINOR(devt));
>
> return 0;
>
> -del_cdev:
> - cdev_del(&pps->cdev);
> -
> free_idr:
> mutex_lock(&pps_idr_lock);
> idr_remove(&pps_idr, pps->id);
> @@ -401,8 +392,9 @@ EXPORT_SYMBOL(pps_lookup_dev);
>
> static void __exit pps_exit(void)
> {
> - class_destroy(pps_class);
> + cdev_del(&pps_cdev);
> unregister_chrdev_region(pps_devt, PPS_MAX_SOURCES);
> + class_destroy(pps_class);
> }
>
> static int __init pps_init(void)
> @@ -422,12 +414,22 @@ static int __init pps_init(void)
> goto remove_class;
> }
>
> + cdev_init(&pps_cdev, &pps_cdev_fops);
> + pps_cdev.owner = THIS_MODULE;
> + err = cdev_add(&pps_cdev, pps_devt, PPS_MAX_SOURCES);
> + if (err < 0) {
> + pr_err("failed to register struct cdev\n");
> + goto remove_region;
> + }
> +
> pr_info("LinuxPPS API ver. %d registered\n", PPS_API_VERS);
> pr_info("Software ver. %s - Copyright 2005-2007 Rodolfo Giometti "
> "<giometti@...ux.it>\n", PPS_VERSION);
>
> return 0;
>
> +remove_region:
> + unregister_chrdev_region(pps_devt, PPS_MAX_SOURCES);
> remove_class:
> class_destroy(pps_class);
>
> diff --git a/include/linux/pps_kernel.h b/include/linux/pps_kernel.h
> index 7db3eb9..caca565 100644
> --- a/include/linux/pps_kernel.h
> +++ b/include/linux/pps_kernel.h
> @@ -70,7 +70,6 @@ struct pps_device {
>
> unsigned int id; /* PPS source unique ID */
> void const *lookup_cookie; /* pps_lookup_dev only */
> - struct cdev cdev;
> struct device *dev;
> struct fasync_struct *async_queue; /* fasync method */
> spinlock_t lock;
--
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