[PATCH v2] pps: Remove embedded cdev to fix a use-after-free

[PATCH v2] pps: Remove embedded cdev to fix a use-after-free

[Calvin Owens]

On a board running ntpd and gpsd, I'm seeing a consistent use-after-free
in sys_exit() from gpsd when rebooting:

    pps pps1: removed
    ------------[ cut here ]------------
    kobject: '(null)' (00000000db4bec24): is not initialized, yet kobject_put() is being called.
    WARNING: CPU: 2 PID: 440 at lib/kobject.c:734 kobject_put+0x120/0x150
    CPU: 2 UID: 299 PID: 440 Comm: gpsd Not tainted 6.11.0-rc6-00308-gb31c44928842 #1
    Hardware name: Raspberry Pi 4 Model B Rev 1.1 (DT)
    pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
    pc : kobject_put+0x120/0x150
    lr : kobject_put+0x120/0x150
    sp : ffffffc0803d3ae0
    x29: ffffffc0803d3ae0 x28: ffffff8042dc9738 x27: 0000000000000001
    x26: 0000000000000000 x25: ffffff8042dc9040 x24: ffffff8042dc9440
    x23: ffffff80402a4620 x22: ffffff8042ef4bd0 x21: ffffff80405cb600
    x20: 000000000008001b x19: ffffff8040b3b6e0 x18: 0000000000000000
    x17: 0000000000000000 x16: 0000000000000000 x15: 696e6920746f6e20
    x14: 7369203a29343263 x13: 205d303434542020 x12: 0000000000000000
    x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000000
    x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
    x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000
    x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000000
    Call trace:
     kobject_put+0x120/0x150
     cdev_put+0x20/0x3c
     __fput+0x2c4/0x2d8
     ____fput+0x1c/0x38
     task_work_run+0x70/0xfc
     do_exit+0x2a0/0x924
     do_group_exit+0x34/0x90
     get_signal+0x7fc/0x8c0
     do_signal+0x128/0x13b4
     do_notify_resume+0xdc/0x160
     el0_svc+0xd4/0xf8
     el0t_64_sync_handler+0x140/0x14c
     el0t_64_sync+0x190/0x194
    ---[ end trace 0000000000000000 ]---

...followed by more symptoms of corruption, with similar stacks:

    refcount_t: underflow; use-after-free.
    kernel BUG at lib/list_debug.c:62!
    Kernel panic - not syncing: Oops - BUG: Fatal exception

This happens because pps_device_destruct() frees the pps_device with the
embedded cdev immediately after calling cdev_del(), but, as the comment
above cdev_del() notes, fops for previously opened cdevs are still
callable even after cdev_del() returns. I think this bug has always
been there: I can't explain why it suddenly started happening every time
I reboot this particular board.

In commit d953e0e837e6 ("pps: Fix a use-after free bug when
unregistering a source."), George Spelvin suggested removing the
embedded cdev. That seems like the simplest way to fix this, so I've
implemented his suggestion, with pps_idr becoming the source of truth
for which minor corresponds to which device.

But now that pps_idr defines userspace visibility instead of cdev_add(),
we need to be sure the pps->dev kobject refcount can't reach zero while
userspace can still find it again. So, the idr_remove() call moves to
pps_unregister_cdev(), and pps_idr now holds a reference to the pps->dev
kobject.

    pps_core: source serial1 got cdev (251:1)
    <...>
    pps pps1: removed
    pps_core: unregistering pps1
    pps_core: deallocating pps1

Fixes: d953e0e837e6 ("pps: Fix a use-after free bug when unregistering a source.")
Cc: stable@vger.kernel.org
Signed-off-by: Calvin Owens <calvin@wbinvd.org>
---
Changes in v2:
- Don't move pr_debug() from pps_device_destruct() to pps_unregister_cdev()
- Actually add stable@vger.kernel.org to CC
---
 drivers/pps/pps.c          | 83 ++++++++++++++++++++------------------
 include/linux/pps_kernel.h |  1 -
 2 files changed, 44 insertions(+), 40 deletions(-)

diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
index 5d19baae6a38..6980ab17f314 100644
--- a/drivers/pps/pps.c
+++ b/drivers/pps/pps.c
@@ -25,7 +25,7 @@
  * Local variables
  */
 
-static dev_t pps_devt;
+static int pps_major;
 static struct class *pps_class;
 
 static DEFINE_MUTEX(pps_idr_lock);
@@ -296,19 +296,35 @@ static long pps_cdev_compat_ioctl(struct file *file,
 #define pps_cdev_compat_ioctl	NULL
 #endif
 
+static struct pps_device *pps_idr_get(unsigned long id)
+{
+	struct pps_device *pps;
+
+	mutex_lock(&pps_idr_lock);
+	pps = idr_find(&pps_idr, id);
+	if (pps)
+		kobject_get(&pps->dev->kobj);
+
+	mutex_unlock(&pps_idr_lock);
+	return pps;
+}
+
 static int pps_cdev_open(struct inode *inode, struct file *file)
 {
-	struct pps_device *pps = container_of(inode->i_cdev,
-						struct pps_device, cdev);
+	struct pps_device *pps = pps_idr_get(iminor(inode));
+
+	if (!pps)
+		return -ENODEV;
+
 	file->private_data = pps;
-	kobject_get(&pps->dev->kobj);
 	return 0;
 }
 
 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;
+
+	WARN_ON(pps->id != iminor(inode));
 	kobject_put(&pps->dev->kobj);
 	return 0;
 }
@@ -332,14 +348,7 @@ 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);
-	idr_remove(&pps_idr, pps->id);
-	mutex_unlock(&pps_idr_lock);
-
 	kfree(dev);
 	kfree(pps);
 }
@@ -364,39 +373,26 @@ int pps_register_cdev(struct pps_device *pps)
 		goto out_unlock;
 	}
 	pps->id = err;
-	mutex_unlock(&pps_idr_lock);
 
-	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;
-	}
+	devt = MKDEV(pps_major, pps->id);
 	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);
+	pr_debug("source %s got cdev (%d:%d)\n", pps->info.name, pps_major,
+		 pps->id);
 
+	kobject_get(&pps->dev->kobj);
+	mutex_unlock(&pps_idr_lock);
 	return 0;
 
-del_cdev:
-	cdev_del(&pps->cdev);
-
 free_idr:
-	mutex_lock(&pps_idr_lock);
 	idr_remove(&pps_idr, pps->id);
 out_unlock:
 	mutex_unlock(&pps_idr_lock);
@@ -408,6 +404,12 @@ void pps_unregister_cdev(struct pps_device *pps)
 	pr_debug("unregistering pps%d\n", pps->id);
 	pps->lookup_cookie = NULL;
 	device_destroy(pps_class, pps->dev->devt);
+
+	/* Now we can release the ID for re-use */
+	mutex_lock(&pps_idr_lock);
+	idr_remove(&pps_idr, pps->id);
+	kobject_put(&pps->dev->kobj);
+	mutex_unlock(&pps_idr_lock);
 }
 
 /*
@@ -427,6 +429,11 @@ void pps_unregister_cdev(struct pps_device *pps)
  * so that it will not be used again, even if the pps device cannot
  * be removed from the idr due to pending references holding the minor
  * number in use.
+ *
+ * Since pps_idr holds a reference to the kobject, the returned
+ * pps_device is guaranteed to be valid until pps_unregister_cdev() is
+ * called on it. But after calling pps_unregister_cdev(), it may be
+ * freed at any time.
  */
 struct pps_device *pps_lookup_dev(void const *cookie)
 {
@@ -449,13 +456,11 @@ EXPORT_SYMBOL(pps_lookup_dev);
 static void __exit pps_exit(void)
 {
 	class_destroy(pps_class);
-	unregister_chrdev_region(pps_devt, PPS_MAX_SOURCES);
+	__unregister_chrdev(pps_major, 0, PPS_MAX_SOURCES, "pps");
 }
 
 static int __init pps_init(void)
 {
-	int err;
-
 	pps_class = class_create("pps");
 	if (IS_ERR(pps_class)) {
 		pr_err("failed to allocate class\n");
@@ -463,8 +468,9 @@ static int __init pps_init(void)
 	}
 	pps_class->dev_groups = pps_groups;
 
-	err = alloc_chrdev_region(&pps_devt, 0, PPS_MAX_SOURCES, "pps");
-	if (err < 0) {
+	pps_major = __register_chrdev(0, 0, PPS_MAX_SOURCES, "pps",
+				      &pps_cdev_fops);
+	if (pps_major < 0) {
 		pr_err("failed to allocate char device region\n");
 		goto remove_class;
 	}
@@ -477,8 +483,7 @@ static int __init pps_init(void)
 
 remove_class:
 	class_destroy(pps_class);
-
-	return err;
+	return pps_major;
 }
 
 subsys_initcall(pps_init);
diff --git a/include/linux/pps_kernel.h b/include/linux/pps_kernel.h
index 78c8ac4951b5..8ee312788118 100644
--- a/include/linux/pps_kernel.h
+++ b/include/linux/pps_kernel.h
@@ -56,7 +56,6 @@ struct pps_device {
 
 	unsigned int id;			/* PPS source unique ID */
 	void const *lookup_cookie;		/* For pps_lookup_dev() only */
-	struct cdev cdev;
 	struct device *dev;
 	struct fasync_struct *async_queue;	/* fasync method */
 	spinlock_t lock;
-- 
2.45.2

Re: [PATCH v2] pps: Remove embedded cdev to fix a use-after-free

[Rodolfo Giometti]

On 14/09/24 02:24, Calvin Owens wrote:
> On a board running ntpd and gpsd, I'm seeing a consistent use-after-free
> in sys_exit() from gpsd when rebooting:
> 
>      pps pps1: removed
>      ------------[ cut here ]------------
>      kobject: '(null)' (00000000db4bec24): is not initialized, yet kobject_put() is being called.
>      WARNING: CPU: 2 PID: 440 at lib/kobject.c:734 kobject_put+0x120/0x150
>      CPU: 2 UID: 299 PID: 440 Comm: gpsd Not tainted 6.11.0-rc6-00308-gb31c44928842 #1
>      Hardware name: Raspberry Pi 4 Model B Rev 1.1 (DT)
>      pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>      pc : kobject_put+0x120/0x150
>      lr : kobject_put+0x120/0x150
>      sp : ffffffc0803d3ae0
>      x29: ffffffc0803d3ae0 x28: ffffff8042dc9738 x27: 0000000000000001
>      x26: 0000000000000000 x25: ffffff8042dc9040 x24: ffffff8042dc9440
>      x23: ffffff80402a4620 x22: ffffff8042ef4bd0 x21: ffffff80405cb600
>      x20: 000000000008001b x19: ffffff8040b3b6e0 x18: 0000000000000000
>      x17: 0000000000000000 x16: 0000000000000000 x15: 696e6920746f6e20
>      x14: 7369203a29343263 x13: 205d303434542020 x12: 0000000000000000
>      x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000000
>      x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
>      x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000
>      x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000000
>      Call trace:
>       kobject_put+0x120/0x150
>       cdev_put+0x20/0x3c
>       __fput+0x2c4/0x2d8
>       ____fput+0x1c/0x38
>       task_work_run+0x70/0xfc
>       do_exit+0x2a0/0x924
>       do_group_exit+0x34/0x90
>       get_signal+0x7fc/0x8c0
>       do_signal+0x128/0x13b4
>       do_notify_resume+0xdc/0x160
>       el0_svc+0xd4/0xf8
>       el0t_64_sync_handler+0x140/0x14c
>       el0t_64_sync+0x190/0x194
>      ---[ end trace 0000000000000000 ]---
> 
> ...followed by more symptoms of corruption, with similar stacks:
> 
>      refcount_t: underflow; use-after-free.
>      kernel BUG at lib/list_debug.c:62!
>      Kernel panic - not syncing: Oops - BUG: Fatal exception
> 
> This happens because pps_device_destruct() frees the pps_device with the
> embedded cdev immediately after calling cdev_del(), but, as the comment
> above cdev_del() notes, fops for previously opened cdevs are still
> callable even after cdev_del() returns. I think this bug has always
> been there: I can't explain why it suddenly started happening every time
> I reboot this particular board.
> 
> In commit d953e0e837e6 ("pps: Fix a use-after free bug when
> unregistering a source."), George Spelvin suggested removing the
> embedded cdev. That seems like the simplest way to fix this, so I've
> implemented his suggestion, with pps_idr becoming the source of truth
> for which minor corresponds to which device.
> 
> But now that pps_idr defines userspace visibility instead of cdev_add(),
> we need to be sure the pps->dev kobject refcount can't reach zero while
> userspace can still find it again. So, the idr_remove() call moves to
> pps_unregister_cdev(), and pps_idr now holds a reference to the pps->dev
> kobject.
> 
>      pps_core: source serial1 got cdev (251:1)
>      <...>
>      pps pps1: removed
>      pps_core: unregistering pps1
>      pps_core: deallocating pps1
> 
> Fixes: d953e0e837e6 ("pps: Fix a use-after free bug when unregistering a source.")
> Cc: stable@vger.kernel.org
> Signed-off-by: Calvin Owens <calvin@wbinvd.org>
> ---
> Changes in v2:
> - Don't move pr_debug() from pps_device_destruct() to pps_unregister_cdev()
> - Actually add stable@vger.kernel.org to CC
> ---
>   drivers/pps/pps.c          | 83 ++++++++++++++++++++------------------
>   include/linux/pps_kernel.h |  1 -
>   2 files changed, 44 insertions(+), 40 deletions(-)
> 
> diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
> index 5d19baae6a38..6980ab17f314 100644
> --- a/drivers/pps/pps.c
> +++ b/drivers/pps/pps.c
> @@ -25,7 +25,7 @@
>    * Local variables
>    */
>   
> -static dev_t pps_devt;
> +static int pps_major;
>   static struct class *pps_class;
>   
>   static DEFINE_MUTEX(pps_idr_lock);
> @@ -296,19 +296,35 @@ static long pps_cdev_compat_ioctl(struct file *file,
>   #define pps_cdev_compat_ioctl	NULL
>   #endif
>   
> +static struct pps_device *pps_idr_get(unsigned long id)
> +{
> +	struct pps_device *pps;
> +
> +	mutex_lock(&pps_idr_lock);
> +	pps = idr_find(&pps_idr, id);
> +	if (pps)
> +		kobject_get(&pps->dev->kobj);
> +
> +	mutex_unlock(&pps_idr_lock);
> +	return pps;
> +}
> +
>   static int pps_cdev_open(struct inode *inode, struct file *file)
>   {
> -	struct pps_device *pps = container_of(inode->i_cdev,
> -						struct pps_device, cdev);
> +	struct pps_device *pps = pps_idr_get(iminor(inode));
> +
> +	if (!pps)
> +		return -ENODEV;
> +
>   	file->private_data = pps;
> -	kobject_get(&pps->dev->kobj);
>   	return 0;
>   }
>   
>   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;
> +
> +	WARN_ON(pps->id != iminor(inode));
>   	kobject_put(&pps->dev->kobj);
>   	return 0;
>   }
> @@ -332,14 +348,7 @@ 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);
> -	idr_remove(&pps_idr, pps->id);
> -	mutex_unlock(&pps_idr_lock);
> -
>   	kfree(dev);
>   	kfree(pps);
>   }
> @@ -364,39 +373,26 @@ int pps_register_cdev(struct pps_device *pps)
>   		goto out_unlock;
>   	}
>   	pps->id = err;
> -	mutex_unlock(&pps_idr_lock);
>   
> -	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;
> -	}
> +	devt = MKDEV(pps_major, pps->id);
>   	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);
> +	pr_debug("source %s got cdev (%d:%d)\n", pps->info.name, pps_major,
> +		 pps->id);
>   
> +	kobject_get(&pps->dev->kobj);
> +	mutex_unlock(&pps_idr_lock);
>   	return 0;
>   
> -del_cdev:
> -	cdev_del(&pps->cdev);
> -
>   free_idr:
> -	mutex_lock(&pps_idr_lock);
>   	idr_remove(&pps_idr, pps->id);
>   out_unlock:
>   	mutex_unlock(&pps_idr_lock);
> @@ -408,6 +404,12 @@ void pps_unregister_cdev(struct pps_device *pps)
>   	pr_debug("unregistering pps%d\n", pps->id);
>   	pps->lookup_cookie = NULL;
>   	device_destroy(pps_class, pps->dev->devt);
> +
> +	/* Now we can release the ID for re-use */
> +	mutex_lock(&pps_idr_lock);
> +	idr_remove(&pps_idr, pps->id);
> +	kobject_put(&pps->dev->kobj);
> +	mutex_unlock(&pps_idr_lock);
>   }
>   
>   /*
> @@ -427,6 +429,11 @@ void pps_unregister_cdev(struct pps_device *pps)
>    * so that it will not be used again, even if the pps device cannot
>    * be removed from the idr due to pending references holding the minor
>    * number in use.
> + *
> + * Since pps_idr holds a reference to the kobject, the returned
> + * pps_device is guaranteed to be valid until pps_unregister_cdev() is
> + * called on it. But after calling pps_unregister_cdev(), it may be
> + * freed at any time.
>    */
>   struct pps_device *pps_lookup_dev(void const *cookie)
>   {
> @@ -449,13 +456,11 @@ EXPORT_SYMBOL(pps_lookup_dev);
>   static void __exit pps_exit(void)
>   {
>   	class_destroy(pps_class);
> -	unregister_chrdev_region(pps_devt, PPS_MAX_SOURCES);
> +	__unregister_chrdev(pps_major, 0, PPS_MAX_SOURCES, "pps");
>   }
>   
>   static int __init pps_init(void)
>   {
> -	int err;
> -
>   	pps_class = class_create("pps");
>   	if (IS_ERR(pps_class)) {
>   		pr_err("failed to allocate class\n");
> @@ -463,8 +468,9 @@ static int __init pps_init(void)
>   	}
>   	pps_class->dev_groups = pps_groups;
>   
> -	err = alloc_chrdev_region(&pps_devt, 0, PPS_MAX_SOURCES, "pps");
> -	if (err < 0) {
> +	pps_major = __register_chrdev(0, 0, PPS_MAX_SOURCES, "pps",
> +				      &pps_cdev_fops);
> +	if (pps_major < 0) {
>   		pr_err("failed to allocate char device region\n");
>   		goto remove_class;
>   	}
> @@ -477,8 +483,7 @@ static int __init pps_init(void)
>   
>   remove_class:
>   	class_destroy(pps_class);
> -
> -	return err;
> +	return pps_major;
>   }
>   
>   subsys_initcall(pps_init);
> diff --git a/include/linux/pps_kernel.h b/include/linux/pps_kernel.h
> index 78c8ac4951b5..8ee312788118 100644
> --- a/include/linux/pps_kernel.h
> +++ b/include/linux/pps_kernel.h
> @@ -56,7 +56,6 @@ struct pps_device {
>   
>   	unsigned int id;			/* PPS source unique ID */
>   	void const *lookup_cookie;		/* For pps_lookup_dev() only */
> -	struct cdev cdev;
>   	struct device *dev;
>   	struct fasync_struct *async_queue;	/* fasync method */
>   	spinlock_t lock;

Acked-by: Rodolfo Giometti <giometti@enneenne.com>

-- 
GNU/Linux Solutions                  e-mail: giometti@enneenne.com
Linux Device Driver                          giometti@linux.it
Embedded Systems                     phone:  +39 349 2432127
UNIX programming

Re: [PATCH v2] pps: Remove embedded cdev to fix a use-after-free

[Greg Kroah-Hartman]

On Fri, Sep 13, 2024 at 05:24:29PM -0700, Calvin Owens wrote:
> On a board running ntpd and gpsd, I'm seeing a consistent use-after-free
> in sys_exit() from gpsd when rebooting:
> 
>     pps pps1: removed
>     ------------[ cut here ]------------
>     kobject: '(null)' (00000000db4bec24): is not initialized, yet kobject_put() is being called.

Something is wrong with the reference counting here...

>     WARNING: CPU: 2 PID: 440 at lib/kobject.c:734 kobject_put+0x120/0x150
>     CPU: 2 UID: 299 PID: 440 Comm: gpsd Not tainted 6.11.0-rc6-00308-gb31c44928842 #1
>     Hardware name: Raspberry Pi 4 Model B Rev 1.1 (DT)
>     pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>     pc : kobject_put+0x120/0x150
>     lr : kobject_put+0x120/0x150
>     sp : ffffffc0803d3ae0
>     x29: ffffffc0803d3ae0 x28: ffffff8042dc9738 x27: 0000000000000001
>     x26: 0000000000000000 x25: ffffff8042dc9040 x24: ffffff8042dc9440
>     x23: ffffff80402a4620 x22: ffffff8042ef4bd0 x21: ffffff80405cb600
>     x20: 000000000008001b x19: ffffff8040b3b6e0 x18: 0000000000000000
>     x17: 0000000000000000 x16: 0000000000000000 x15: 696e6920746f6e20
>     x14: 7369203a29343263 x13: 205d303434542020 x12: 0000000000000000
>     x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000000
>     x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
>     x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000
>     x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000000
>     Call trace:
>      kobject_put+0x120/0x150
>      cdev_put+0x20/0x3c
>      __fput+0x2c4/0x2d8
>      ____fput+0x1c/0x38
>      task_work_run+0x70/0xfc
>      do_exit+0x2a0/0x924
>      do_group_exit+0x34/0x90
>      get_signal+0x7fc/0x8c0
>      do_signal+0x128/0x13b4
>      do_notify_resume+0xdc/0x160
>      el0_svc+0xd4/0xf8
>      el0t_64_sync_handler+0x140/0x14c
>      el0t_64_sync+0x190/0x194
>     ---[ end trace 0000000000000000 ]---
> 
> ...followed by more symptoms of corruption, with similar stacks:
> 
>     refcount_t: underflow; use-after-free.
>     kernel BUG at lib/list_debug.c:62!
>     Kernel panic - not syncing: Oops - BUG: Fatal exception
> 
> This happens because pps_device_destruct() frees the pps_device with the
> embedded cdev immediately after calling cdev_del(), but, as the comment
> above cdev_del() notes, fops for previously opened cdevs are still
> callable even after cdev_del() returns. I think this bug has always
> been there: I can't explain why it suddenly started happening every time
> I reboot this particular board.
> 
> In commit d953e0e837e6 ("pps: Fix a use-after free bug when
> unregistering a source."), George Spelvin suggested removing the
> embedded cdev. That seems like the simplest way to fix this, so I've
> implemented his suggestion, with pps_idr becoming the source of truth
> for which minor corresponds to which device.

You remove it, but now the structure has no reference counting at all,
so you should make it a real "struct device" not just containing a
pointer to one.

> But now that pps_idr defines userspace visibility instead of cdev_add(),
> we need to be sure the pps->dev kobject refcount can't reach zero while
> userspace can still find it again. So, the idr_remove() call moves to
> pps_unregister_cdev(), and pps_idr now holds a reference to the pps->dev
> kobject.

An idr shouldn't be doing the reference counting here, the struct device
should be doing it, right?


> 
>     pps_core: source serial1 got cdev (251:1)
>     <...>
>     pps pps1: removed
>     pps_core: unregistering pps1
>     pps_core: deallocating pps1
> 
> Fixes: d953e0e837e6 ("pps: Fix a use-after free bug when unregistering a source.")
> Cc: stable@vger.kernel.org
> Signed-off-by: Calvin Owens <calvin@wbinvd.org>
> ---
> Changes in v2:
> - Don't move pr_debug() from pps_device_destruct() to pps_unregister_cdev()
> - Actually add stable@vger.kernel.org to CC
> ---
>  drivers/pps/pps.c          | 83 ++++++++++++++++++++------------------
>  include/linux/pps_kernel.h |  1 -
>  2 files changed, 44 insertions(+), 40 deletions(-)
> 
> diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
> index 5d19baae6a38..6980ab17f314 100644
> --- a/drivers/pps/pps.c
> +++ b/drivers/pps/pps.c
> @@ -25,7 +25,7 @@
>   * Local variables
>   */
>  
> -static dev_t pps_devt;
> +static int pps_major;
>  static struct class *pps_class;
>  
>  static DEFINE_MUTEX(pps_idr_lock);
> @@ -296,19 +296,35 @@ static long pps_cdev_compat_ioctl(struct file *file,
>  #define pps_cdev_compat_ioctl	NULL
>  #endif
>  
> +static struct pps_device *pps_idr_get(unsigned long id)
> +{
> +	struct pps_device *pps;
> +
> +	mutex_lock(&pps_idr_lock);
> +	pps = idr_find(&pps_idr, id);
> +	if (pps)
> +		kobject_get(&pps->dev->kobj);

A driver should never call "raw" kobject calls, this alone makes this
not ok :(

Please move the structure to be embedded in and then it should be
simpler.

thanks,

greg k-h

Re: [PATCH v2] pps: Remove embedded cdev to fix a use-after-free

[Calvin Owens]

Hi Greg,

On Sunday 10/13 at 17:04 +0200, Greg Kroah-Hartman wrote:
> On Fri, Sep 13, 2024 at 05:24:29PM -0700, Calvin Owens wrote:
> > On a board running ntpd and gpsd, I'm seeing a consistent use-after-free
> > in sys_exit() from gpsd when rebooting:
> > 
> >     pps pps1: removed
> >     ------------[ cut here ]------------
> >     kobject: '(null)' (00000000db4bec24): is not initialized, yet kobject_put() is being called.
> 
> Something is wrong with the reference counting here...
> 
> >     WARNING: CPU: 2 PID: 440 at lib/kobject.c:734 kobject_put+0x120/0x150
> >     CPU: 2 UID: 299 PID: 440 Comm: gpsd Not tainted 6.11.0-rc6-00308-gb31c44928842 #1
> >     Hardware name: Raspberry Pi 4 Model B Rev 1.1 (DT)
> >     pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> >     pc : kobject_put+0x120/0x150
> >     lr : kobject_put+0x120/0x150
> >     sp : ffffffc0803d3ae0
> >     x29: ffffffc0803d3ae0 x28: ffffff8042dc9738 x27: 0000000000000001
> >     x26: 0000000000000000 x25: ffffff8042dc9040 x24: ffffff8042dc9440
> >     x23: ffffff80402a4620 x22: ffffff8042ef4bd0 x21: ffffff80405cb600
> >     x20: 000000000008001b x19: ffffff8040b3b6e0 x18: 0000000000000000
> >     x17: 0000000000000000 x16: 0000000000000000 x15: 696e6920746f6e20
> >     x14: 7369203a29343263 x13: 205d303434542020 x12: 0000000000000000
> >     x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000000
> >     x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
> >     x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000
> >     x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000000
> >     Call trace:
> >      kobject_put+0x120/0x150
> >      cdev_put+0x20/0x3c
> >      __fput+0x2c4/0x2d8
> >      ____fput+0x1c/0x38
> >      task_work_run+0x70/0xfc
> >      do_exit+0x2a0/0x924
> >      do_group_exit+0x34/0x90
> >      get_signal+0x7fc/0x8c0
> >      do_signal+0x128/0x13b4
> >      do_notify_resume+0xdc/0x160
> >      el0_svc+0xd4/0xf8
> >      el0t_64_sync_handler+0x140/0x14c
> >      el0t_64_sync+0x190/0x194
> >     ---[ end trace 0000000000000000 ]---
> > 
> > ...followed by more symptoms of corruption, with similar stacks:
> > 
> >     refcount_t: underflow; use-after-free.
> >     kernel BUG at lib/list_debug.c:62!
> >     Kernel panic - not syncing: Oops - BUG: Fatal exception
> > 
> > This happens because pps_device_destruct() frees the pps_device with the
> > embedded cdev immediately after calling cdev_del(), but, as the comment
> > above cdev_del() notes, fops for previously opened cdevs are still
> > callable even after cdev_del() returns. I think this bug has always
> > been there: I can't explain why it suddenly started happening every time
> > I reboot this particular board.
> > 
> > In commit d953e0e837e6 ("pps: Fix a use-after free bug when
> > unregistering a source."), George Spelvin suggested removing the
> > embedded cdev. That seems like the simplest way to fix this, so I've
> > implemented his suggestion, with pps_idr becoming the source of truth
> > for which minor corresponds to which device.
> 
> You remove it, but now the structure has no reference counting at all,
> so you should make it a real "struct device" not just containing a
> pointer to one.

It still uses the device refcount. I didn't change that, see the
kobject_get() (which is confusing and should be get_device() as you note
below) in pps_cdev_open() before my patch.

> > But now that pps_idr defines userspace visibility instead of cdev_add(),
> > we need to be sure the pps->dev kobject refcount can't reach zero while
> > userspace can still find it again. So, the idr_remove() call moves to
> > pps_unregister_cdev(), and pps_idr now holds a reference to the pps->dev
> > kobject.
> 
> An idr shouldn't be doing the reference counting here, the struct device
> should be doing it, right?

Right, I was trying to explain that it is now necessary to call
get_device() to acquire a reference while the device minor is indexed by
the idr.

Before, the minor was deindexed in the idr in ->release(). But now,
since it is visible the moment it is indexed by the idr, deindexing it
in ->release() means this could happen during removal:

	CPU1		CPU2
	---		---
			pps_unregister_cdev()
			<...>
	sys_open()
	<...>
	idr_lookup()
			idr_remove()
			put_device() <--- ref goes to zero
	get_device()		     <--- BOOM
			pps_device_destruct()
			pps_idr_remove()

By calling get_device() in pps_idr_get(), and by moving the idr
deindexing from ->release() to pps_unregister_cdev(), we ensure that
can't happen.

> > 
> >     pps_core: source serial1 got cdev (251:1)
> >     <...>
> >     pps pps1: removed
> >     pps_core: unregistering pps1
> >     pps_core: deallocating pps1
> > 
> > Fixes: d953e0e837e6 ("pps: Fix a use-after free bug when unregistering a source.")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Calvin Owens <calvin@wbinvd.org>
> > ---
> > Changes in v2:
> > - Don't move pr_debug() from pps_device_destruct() to pps_unregister_cdev()
> > - Actually add stable@vger.kernel.org to CC
> > ---
> >  drivers/pps/pps.c          | 83 ++++++++++++++++++++------------------
> >  include/linux/pps_kernel.h |  1 -
> >  2 files changed, 44 insertions(+), 40 deletions(-)
> > 
> > diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
> > index 5d19baae6a38..6980ab17f314 100644
> > --- a/drivers/pps/pps.c
> > +++ b/drivers/pps/pps.c
> > @@ -25,7 +25,7 @@
> >   * Local variables
> >   */
> >  
> > -static dev_t pps_devt;
> > +static int pps_major;
> >  static struct class *pps_class;
> >  
> >  static DEFINE_MUTEX(pps_idr_lock);
> > @@ -296,19 +296,35 @@ static long pps_cdev_compat_ioctl(struct file *file,
> >  #define pps_cdev_compat_ioctl	NULL
> >  #endif
> >  
> > +static struct pps_device *pps_idr_get(unsigned long id)
> > +{
> > +	struct pps_device *pps;
> > +
> > +	mutex_lock(&pps_idr_lock);
> > +	pps = idr_find(&pps_idr, id);
> > +	if (pps)
> > +		kobject_get(&pps->dev->kobj);
> 
> A driver should never call "raw" kobject calls, this alone makes this
> not ok :(

Oh this is silly, sorry: it's simply open coding put_device() and
get_device(), I'll fix that.

> Please move the structure to be embedded in and then it should be
> simpler.

I actually tried to do that, but got hung up on the API: what's the
right way to do what device_create() does for an embedded device struct?

Today, the pps core does:

	pps = kzalloc(sizeof(*pps));

...then later in pps_register_cdev():

	idr_alloc(&newmin, ...);
	pps->dev = device_create(..., MKDEV(maj, newmin), ...);

To embed the device struct, I guess this would become something like:

	pps = kzalloc(sizeof(*pps));
	device_initialize(&pps->dev);
	idr_alloc(&newmin, ...);
	/* ??? */
	device_register(&pps->dev);

...but the question marks are what I'm not seeing: what's the proper way
to accomplish what device_create() does, but in an embedded dev struct?
Obviously I could just copy device_create(), but I'm sure that's not
what you want.

Thanks,
Calvin

> thanks,
> 
> greg k-h

[PATCH v3] pps: Fix a use-after-free

[Calvin Owens]

On a board running ntpd and gpsd, I'm seeing a consistent use-after-free
in sys_exit() from gpsd when rebooting:

    pps pps1: removed
    ------------[ cut here ]------------
    kobject: '(null)' (00000000db4bec24): is not initialized, yet kobject_put() is being called.
    WARNING: CPU: 2 PID: 440 at lib/kobject.c:734 kobject_put+0x120/0x150
    CPU: 2 UID: 299 PID: 440 Comm: gpsd Not tainted 6.11.0-rc6-00308-gb31c44928842 #1
    Hardware name: Raspberry Pi 4 Model B Rev 1.1 (DT)
    pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
    pc : kobject_put+0x120/0x150
    lr : kobject_put+0x120/0x150
    sp : ffffffc0803d3ae0
    x29: ffffffc0803d3ae0 x28: ffffff8042dc9738 x27: 0000000000000001
    x26: 0000000000000000 x25: ffffff8042dc9040 x24: ffffff8042dc9440
    x23: ffffff80402a4620 x22: ffffff8042ef4bd0 x21: ffffff80405cb600
    x20: 000000000008001b x19: ffffff8040b3b6e0 x18: 0000000000000000
    x17: 0000000000000000 x16: 0000000000000000 x15: 696e6920746f6e20
    x14: 7369203a29343263 x13: 205d303434542020 x12: 0000000000000000
    x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000000
    x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
    x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000
    x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000000
    Call trace:
     kobject_put+0x120/0x150
     cdev_put+0x20/0x3c
     __fput+0x2c4/0x2d8
     ____fput+0x1c/0x38
     task_work_run+0x70/0xfc
     do_exit+0x2a0/0x924
     do_group_exit+0x34/0x90
     get_signal+0x7fc/0x8c0
     do_signal+0x128/0x13b4
     do_notify_resume+0xdc/0x160
     el0_svc+0xd4/0xf8
     el0t_64_sync_handler+0x140/0x14c
     el0t_64_sync+0x190/0x194
    ---[ end trace 0000000000000000 ]---

...followed by more symptoms of corruption, with similar stacks:

    refcount_t: underflow; use-after-free.
    kernel BUG at lib/list_debug.c:62!
    Kernel panic - not syncing: Oops - BUG: Fatal exception

This happens because pps_device_destruct() frees the pps_device with the
embedded cdev immediately after calling cdev_del(), but, as the comment
above cdev_del() notes, fops for previously opened cdevs are still
callable even after cdev_del() returns. I think this bug has always
been there: I can't explain why it suddenly started happening every time
I reboot this particular board.

In commit d953e0e837e6 ("pps: Fix a use-after free bug when
unregistering a source."), George Spelvin suggested removing the
embedded cdev. That seems like the simplest way to fix this, so I've
implemented his suggestion, using __register_chrdev() with pps_idr
becoming the source of truth for which minor corresponds to which
device.

But now that pps_idr defines userspace visibility instead of cdev_add(),
we need to be sure the pps->dev refcount can't reach zero while
userspace can still find it again. So, the idr_remove() call moves to
pps_unregister_cdev(), and pps_idr now holds a reference to pps->dev.

    pps_core: source serial1 got cdev (251:1)
    <...>
    pps pps1: removed
    pps_core: unregistering pps1
    pps_core: deallocating pps1

Fixes: d953e0e837e6 ("pps: Fix a use-after free bug when unregistering a source.")
Cc: stable@vger.kernel.org
Signed-off-by: Calvin Owens <calvin@wbinvd.org>
---
Changes in v3:
- Shorten patch title
- Embed the device struct in the pps struct
- Use foo_device(&pps->dev) instead of kobject_foo(&pps->dev.kobj)
Changes in v2:
- Don't move pr_debug() from pps_device_destruct() to pps_unregister_cdev()
- Actually add stable@vger.kernel.org to CC
---
 drivers/pps/clients/pps-gpio.c    |   2 +-
 drivers/pps/clients/pps-ktimer.c  |   4 +-
 drivers/pps/clients/pps-ldisc.c   |   6 +-
 drivers/pps/clients/pps_parport.c |   4 +-
 drivers/pps/kapi.c                |  10 +--
 drivers/pps/kc.c                  |  10 +--
 drivers/pps/pps.c                 | 127 ++++++++++++++++--------------
 include/linux/pps_kernel.h        |   3 +-
 8 files changed, 85 insertions(+), 81 deletions(-)

diff --git a/drivers/pps/clients/pps-gpio.c b/drivers/pps/clients/pps-gpio.c
index 791fdc9326dd..a21bf56e7a87 100644
--- a/drivers/pps/clients/pps-gpio.c
+++ b/drivers/pps/clients/pps-gpio.c
@@ -214,7 +214,7 @@ static int pps_gpio_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}
 
-	dev_info(data->pps->dev, "Registered IRQ %d as PPS source\n",
+	dev_info(&data->pps->dev, "Registered IRQ %d as PPS source\n",
 		 data->irq);
 
 	return 0;
diff --git a/drivers/pps/clients/pps-ktimer.c b/drivers/pps/clients/pps-ktimer.c
index d33106bd7a29..00cf406377a1 100644
--- a/drivers/pps/clients/pps-ktimer.c
+++ b/drivers/pps/clients/pps-ktimer.c
@@ -56,7 +56,7 @@ static struct pps_source_info pps_ktimer_info = {
 
 static void __exit pps_ktimer_exit(void)
 {
-	dev_info(pps->dev, "ktimer PPS source unregistered\n");
+	dev_info(&pps->dev, "ktimer PPS source unregistered\n");
 
 	del_timer_sync(&ktimer);
 	pps_unregister_source(pps);
@@ -74,7 +74,7 @@ static int __init pps_ktimer_init(void)
 	timer_setup(&ktimer, pps_ktimer_event, 0);
 	mod_timer(&ktimer, jiffies + HZ);
 
-	dev_info(pps->dev, "ktimer PPS source registered\n");
+	dev_info(&pps->dev, "ktimer PPS source registered\n");
 
 	return 0;
 }
diff --git a/drivers/pps/clients/pps-ldisc.c b/drivers/pps/clients/pps-ldisc.c
index 443d6bae19d1..49ae33cca03d 100644
--- a/drivers/pps/clients/pps-ldisc.c
+++ b/drivers/pps/clients/pps-ldisc.c
@@ -32,7 +32,7 @@ static void pps_tty_dcd_change(struct tty_struct *tty, bool active)
 	pps_event(pps, &ts, active ? PPS_CAPTUREASSERT :
 			PPS_CAPTURECLEAR, NULL);
 
-	dev_dbg(pps->dev, "PPS %s at %lu\n",
+	dev_dbg(&pps->dev, "PPS %s at %lu\n",
 			active ? "assert" : "clear", jiffies);
 }
 
@@ -69,7 +69,7 @@ static int pps_tty_open(struct tty_struct *tty)
 		goto err_unregister;
 	}
 
-	dev_info(pps->dev, "source \"%s\" added\n", info.path);
+	dev_info(&pps->dev, "source \"%s\" added\n", info.path);
 
 	return 0;
 
@@ -89,7 +89,7 @@ static void pps_tty_close(struct tty_struct *tty)
 	if (WARN_ON(!pps))
 		return;
 
-	dev_info(pps->dev, "removed\n");
+	dev_info(&pps->dev, "removed\n");
 	pps_unregister_source(pps);
 }
 
diff --git a/drivers/pps/clients/pps_parport.c b/drivers/pps/clients/pps_parport.c
index abaffb4e1c1c..24db06750297 100644
--- a/drivers/pps/clients/pps_parport.c
+++ b/drivers/pps/clients/pps_parport.c
@@ -81,7 +81,7 @@ static void parport_irq(void *handle)
 	/* check the signal (no signal means the pulse is lost this time) */
 	if (!signal_is_set(port)) {
 		local_irq_restore(flags);
-		dev_err(dev->pps->dev, "lost the signal\n");
+		dev_err(&dev->pps->dev, "lost the signal\n");
 		goto out_assert;
 	}
 
@@ -98,7 +98,7 @@ static void parport_irq(void *handle)
 	/* timeout */
 	dev->cw_err++;
 	if (dev->cw_err >= CLEAR_WAIT_MAX_ERRORS) {
-		dev_err(dev->pps->dev, "disabled clear edge capture after %d"
+		dev_err(&dev->pps->dev, "disabled clear edge capture after %d"
 				" timeouts\n", dev->cw_err);
 		dev->cw = 0;
 		dev->cw_err = 0;
diff --git a/drivers/pps/kapi.c b/drivers/pps/kapi.c
index d9d566f70ed1..a76685c147ee 100644
--- a/drivers/pps/kapi.c
+++ b/drivers/pps/kapi.c
@@ -41,7 +41,7 @@ static void pps_add_offset(struct pps_ktime *ts, struct pps_ktime *offset)
 static void pps_echo_client_default(struct pps_device *pps, int event,
 		void *data)
 {
-	dev_info(pps->dev, "echo %s %s\n",
+	dev_info(&pps->dev, "echo %s %s\n",
 		event & PPS_CAPTUREASSERT ? "assert" : "",
 		event & PPS_CAPTURECLEAR ? "clear" : "");
 }
@@ -112,7 +112,7 @@ struct pps_device *pps_register_source(struct pps_source_info *info,
 		goto kfree_pps;
 	}
 
-	dev_info(pps->dev, "new PPS source %s\n", info->name);
+	dev_info(&pps->dev, "new PPS source %s\n", info->name);
 
 	return pps;
 
@@ -166,7 +166,7 @@ void pps_event(struct pps_device *pps, struct pps_event_time *ts, int event,
 	/* check event type */
 	BUG_ON((event & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR)) == 0);
 
-	dev_dbg(pps->dev, "PPS event at %lld.%09ld\n",
+	dev_dbg(&pps->dev, "PPS event at %lld.%09ld\n",
 			(s64)ts->ts_real.tv_sec, ts->ts_real.tv_nsec);
 
 	timespec_to_pps_ktime(&ts_real, ts->ts_real);
@@ -188,7 +188,7 @@ void pps_event(struct pps_device *pps, struct pps_event_time *ts, int event,
 		/* Save the time stamp */
 		pps->assert_tu = ts_real;
 		pps->assert_sequence++;
-		dev_dbg(pps->dev, "capture assert seq #%u\n",
+		dev_dbg(&pps->dev, "capture assert seq #%u\n",
 			pps->assert_sequence);
 
 		captured = ~0;
@@ -202,7 +202,7 @@ void pps_event(struct pps_device *pps, struct pps_event_time *ts, int event,
 		/* Save the time stamp */
 		pps->clear_tu = ts_real;
 		pps->clear_sequence++;
-		dev_dbg(pps->dev, "capture clear seq #%u\n",
+		dev_dbg(&pps->dev, "capture clear seq #%u\n",
 			pps->clear_sequence);
 
 		captured = ~0;
diff --git a/drivers/pps/kc.c b/drivers/pps/kc.c
index 50dc59af45be..fbd23295afd7 100644
--- a/drivers/pps/kc.c
+++ b/drivers/pps/kc.c
@@ -43,11 +43,11 @@ int pps_kc_bind(struct pps_device *pps, struct pps_bind_args *bind_args)
 			pps_kc_hardpps_mode = 0;
 			pps_kc_hardpps_dev = NULL;
 			spin_unlock_irq(&pps_kc_hardpps_lock);
-			dev_info(pps->dev, "unbound kernel"
+			dev_info(&pps->dev, "unbound kernel"
 					" consumer\n");
 		} else {
 			spin_unlock_irq(&pps_kc_hardpps_lock);
-			dev_err(pps->dev, "selected kernel consumer"
+			dev_err(&pps->dev, "selected kernel consumer"
 					" is not bound\n");
 			return -EINVAL;
 		}
@@ -57,11 +57,11 @@ int pps_kc_bind(struct pps_device *pps, struct pps_bind_args *bind_args)
 			pps_kc_hardpps_mode = bind_args->edge;
 			pps_kc_hardpps_dev = pps;
 			spin_unlock_irq(&pps_kc_hardpps_lock);
-			dev_info(pps->dev, "bound kernel consumer: "
+			dev_info(&pps->dev, "bound kernel consumer: "
 				"edge=0x%x\n", bind_args->edge);
 		} else {
 			spin_unlock_irq(&pps_kc_hardpps_lock);
-			dev_err(pps->dev, "another kernel consumer"
+			dev_err(&pps->dev, "another kernel consumer"
 					" is already bound\n");
 			return -EINVAL;
 		}
@@ -83,7 +83,7 @@ void pps_kc_remove(struct pps_device *pps)
 		pps_kc_hardpps_mode = 0;
 		pps_kc_hardpps_dev = NULL;
 		spin_unlock_irq(&pps_kc_hardpps_lock);
-		dev_info(pps->dev, "unbound kernel consumer"
+		dev_info(&pps->dev, "unbound kernel consumer"
 				" on device removal\n");
 	} else
 		spin_unlock_irq(&pps_kc_hardpps_lock);
diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
index 25d47907db17..6a02245ea35f 100644
--- a/drivers/pps/pps.c
+++ b/drivers/pps/pps.c
@@ -25,7 +25,7 @@
  * Local variables
  */
 
-static dev_t pps_devt;
+static int pps_major;
 static struct class *pps_class;
 
 static DEFINE_MUTEX(pps_idr_lock);
@@ -62,7 +62,7 @@ static int pps_cdev_pps_fetch(struct pps_device *pps, struct pps_fdata *fdata)
 	else {
 		unsigned long ticks;
 
-		dev_dbg(pps->dev, "timeout %lld.%09d\n",
+		dev_dbg(&pps->dev, "timeout %lld.%09d\n",
 				(long long) fdata->timeout.sec,
 				fdata->timeout.nsec);
 		ticks = fdata->timeout.sec * HZ;
@@ -80,7 +80,7 @@ static int pps_cdev_pps_fetch(struct pps_device *pps, struct pps_fdata *fdata)
 
 	/* Check for pending signals */
 	if (err == -ERESTARTSYS) {
-		dev_dbg(pps->dev, "pending signal caught\n");
+		dev_dbg(&pps->dev, "pending signal caught\n");
 		return -EINTR;
 	}
 
@@ -98,7 +98,7 @@ static long pps_cdev_ioctl(struct file *file,
 
 	switch (cmd) {
 	case PPS_GETPARAMS:
-		dev_dbg(pps->dev, "PPS_GETPARAMS\n");
+		dev_dbg(&pps->dev, "PPS_GETPARAMS\n");
 
 		spin_lock_irq(&pps->lock);
 
@@ -114,7 +114,7 @@ static long pps_cdev_ioctl(struct file *file,
 		break;
 
 	case PPS_SETPARAMS:
-		dev_dbg(pps->dev, "PPS_SETPARAMS\n");
+		dev_dbg(&pps->dev, "PPS_SETPARAMS\n");
 
 		/* Check the capabilities */
 		if (!capable(CAP_SYS_TIME))
@@ -124,14 +124,14 @@ static long pps_cdev_ioctl(struct file *file,
 		if (err)
 			return -EFAULT;
 		if (!(params.mode & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR))) {
-			dev_dbg(pps->dev, "capture mode unspecified (%x)\n",
+			dev_dbg(&pps->dev, "capture mode unspecified (%x)\n",
 								params.mode);
 			return -EINVAL;
 		}
 
 		/* Check for supported capabilities */
 		if ((params.mode & ~pps->info.mode) != 0) {
-			dev_dbg(pps->dev, "unsupported capabilities (%x)\n",
+			dev_dbg(&pps->dev, "unsupported capabilities (%x)\n",
 								params.mode);
 			return -EINVAL;
 		}
@@ -144,7 +144,7 @@ static long pps_cdev_ioctl(struct file *file,
 		/* Restore the read only parameters */
 		if ((params.mode & (PPS_TSFMT_TSPEC | PPS_TSFMT_NTPFP)) == 0) {
 			/* section 3.3 of RFC 2783 interpreted */
-			dev_dbg(pps->dev, "time format unspecified (%x)\n",
+			dev_dbg(&pps->dev, "time format unspecified (%x)\n",
 								params.mode);
 			pps->params.mode |= PPS_TSFMT_TSPEC;
 		}
@@ -165,7 +165,7 @@ static long pps_cdev_ioctl(struct file *file,
 		break;
 
 	case PPS_GETCAP:
-		dev_dbg(pps->dev, "PPS_GETCAP\n");
+		dev_dbg(&pps->dev, "PPS_GETCAP\n");
 
 		err = put_user(pps->info.mode, iuarg);
 		if (err)
@@ -176,7 +176,7 @@ static long pps_cdev_ioctl(struct file *file,
 	case PPS_FETCH: {
 		struct pps_fdata fdata;
 
-		dev_dbg(pps->dev, "PPS_FETCH\n");
+		dev_dbg(&pps->dev, "PPS_FETCH\n");
 
 		err = copy_from_user(&fdata, uarg, sizeof(struct pps_fdata));
 		if (err)
@@ -206,7 +206,7 @@ static long pps_cdev_ioctl(struct file *file,
 	case PPS_KC_BIND: {
 		struct pps_bind_args bind_args;
 
-		dev_dbg(pps->dev, "PPS_KC_BIND\n");
+		dev_dbg(&pps->dev, "PPS_KC_BIND\n");
 
 		/* Check the capabilities */
 		if (!capable(CAP_SYS_TIME))
@@ -218,7 +218,7 @@ static long pps_cdev_ioctl(struct file *file,
 
 		/* Check for supported capabilities */
 		if ((bind_args.edge & ~pps->info.mode) != 0) {
-			dev_err(pps->dev, "unsupported capabilities (%x)\n",
+			dev_err(&pps->dev, "unsupported capabilities (%x)\n",
 					bind_args.edge);
 			return -EINVAL;
 		}
@@ -227,7 +227,7 @@ static long pps_cdev_ioctl(struct file *file,
 		if (bind_args.tsformat != PPS_TSFMT_TSPEC ||
 				(bind_args.edge & ~PPS_CAPTUREBOTH) != 0 ||
 				bind_args.consumer != PPS_KC_HARDPPS) {
-			dev_err(pps->dev, "invalid kernel consumer bind"
+			dev_err(&pps->dev, "invalid kernel consumer bind"
 					" parameters (%x)\n", bind_args.edge);
 			return -EINVAL;
 		}
@@ -259,7 +259,7 @@ static long pps_cdev_compat_ioctl(struct file *file,
 		struct pps_fdata fdata;
 		int err;
 
-		dev_dbg(pps->dev, "PPS_FETCH\n");
+		dev_dbg(&pps->dev, "PPS_FETCH\n");
 
 		err = copy_from_user(&compat, uarg, sizeof(struct pps_fdata_compat));
 		if (err)
@@ -296,20 +296,36 @@ static long pps_cdev_compat_ioctl(struct file *file,
 #define pps_cdev_compat_ioctl	NULL
 #endif
 
+static struct pps_device *pps_idr_get(unsigned long id)
+{
+	struct pps_device *pps;
+
+	mutex_lock(&pps_idr_lock);
+	pps = idr_find(&pps_idr, id);
+	if (pps)
+		get_device(&pps->dev);
+
+	mutex_unlock(&pps_idr_lock);
+	return pps;
+}
+
 static int pps_cdev_open(struct inode *inode, struct file *file)
 {
-	struct pps_device *pps = container_of(inode->i_cdev,
-						struct pps_device, cdev);
+	struct pps_device *pps = pps_idr_get(iminor(inode));
+
+	if (!pps)
+		return -ENODEV;
+
 	file->private_data = pps;
-	kobject_get(&pps->dev->kobj);
 	return 0;
 }
 
 static int pps_cdev_release(struct inode *inode, struct file *file)
 {
-	struct pps_device *pps = container_of(inode->i_cdev,
-						struct pps_device, cdev);
-	kobject_put(&pps->dev->kobj);
+	struct pps_device *pps = file->private_data;
+
+	WARN_ON(pps->id != iminor(inode));
+	put_device(&pps->dev);
 	return 0;
 }
 
@@ -331,22 +347,13 @@ 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);
-	idr_remove(&pps_idr, pps->id);
-	mutex_unlock(&pps_idr_lock);
-
-	kfree(dev);
 	kfree(pps);
 }
 
 int pps_register_cdev(struct pps_device *pps)
 {
 	int err;
-	dev_t devt;
 
 	mutex_lock(&pps_idr_lock);
 	/*
@@ -363,40 +370,29 @@ int pps_register_cdev(struct pps_device *pps)
 		goto out_unlock;
 	}
 	pps->id = err;
-	mutex_unlock(&pps_idr_lock);
-
-	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);
+	pps->dev.class = pps_class;
+	pps->dev.parent = pps->info.dev;
+	pps->dev.devt = MKDEV(pps_major, pps->id);
+	dev_set_drvdata(&pps->dev, pps);
+	dev_set_name(&pps->dev, "pps%d", pps->id);
+	err = device_register(&pps->dev);
+	if (err)
 		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;
-	}
 
 	/* Override the release function with our own */
-	pps->dev->release = pps_device_destruct;
+	pps->dev.release = pps_device_destruct;
 
-	pr_debug("source %s got cdev (%d:%d)\n", pps->info.name,
-			MAJOR(pps_devt), pps->id);
+	pr_debug("source %s got cdev (%d:%d)\n", pps->info.name, pps_major,
+		 pps->id);
 
+	get_device(&pps->dev);
+	mutex_unlock(&pps_idr_lock);
 	return 0;
 
-del_cdev:
-	cdev_del(&pps->cdev);
-
 free_idr:
-	mutex_lock(&pps_idr_lock);
 	idr_remove(&pps_idr, pps->id);
+	put_device(&pps->dev);
 out_unlock:
 	mutex_unlock(&pps_idr_lock);
 	return err;
@@ -406,7 +402,13 @@ void pps_unregister_cdev(struct pps_device *pps)
 {
 	pr_debug("unregistering pps%d\n", pps->id);
 	pps->lookup_cookie = NULL;
-	device_destroy(pps_class, pps->dev->devt);
+	device_destroy(pps_class, pps->dev.devt);
+
+	/* Now we can release the ID for re-use */
+	mutex_lock(&pps_idr_lock);
+	idr_remove(&pps_idr, pps->id);
+	put_device(&pps->dev);
+	mutex_unlock(&pps_idr_lock);
 }
 
 /*
@@ -426,6 +428,11 @@ void pps_unregister_cdev(struct pps_device *pps)
  * so that it will not be used again, even if the pps device cannot
  * be removed from the idr due to pending references holding the minor
  * number in use.
+ *
+ * Since pps_idr holds a reference to the device, the returned
+ * pps_device is guaranteed to be valid until pps_unregister_cdev() is
+ * called on it. But after calling pps_unregister_cdev(), it may be
+ * freed at any time.
  */
 struct pps_device *pps_lookup_dev(void const *cookie)
 {
@@ -448,13 +455,11 @@ EXPORT_SYMBOL(pps_lookup_dev);
 static void __exit pps_exit(void)
 {
 	class_destroy(pps_class);
-	unregister_chrdev_region(pps_devt, PPS_MAX_SOURCES);
+	__unregister_chrdev(pps_major, 0, PPS_MAX_SOURCES, "pps");
 }
 
 static int __init pps_init(void)
 {
-	int err;
-
 	pps_class = class_create("pps");
 	if (IS_ERR(pps_class)) {
 		pr_err("failed to allocate class\n");
@@ -462,8 +467,9 @@ static int __init pps_init(void)
 	}
 	pps_class->dev_groups = pps_groups;
 
-	err = alloc_chrdev_region(&pps_devt, 0, PPS_MAX_SOURCES, "pps");
-	if (err < 0) {
+	pps_major = __register_chrdev(0, 0, PPS_MAX_SOURCES, "pps",
+				      &pps_cdev_fops);
+	if (pps_major < 0) {
 		pr_err("failed to allocate char device region\n");
 		goto remove_class;
 	}
@@ -476,8 +482,7 @@ static int __init pps_init(void)
 
 remove_class:
 	class_destroy(pps_class);
-
-	return err;
+	return pps_major;
 }
 
 subsys_initcall(pps_init);
diff --git a/include/linux/pps_kernel.h b/include/linux/pps_kernel.h
index 78c8ac4951b5..c7abce28ed29 100644
--- a/include/linux/pps_kernel.h
+++ b/include/linux/pps_kernel.h
@@ -56,8 +56,7 @@ struct pps_device {
 
 	unsigned int id;			/* PPS source unique ID */
 	void const *lookup_cookie;		/* For pps_lookup_dev() only */
-	struct cdev cdev;
-	struct device *dev;
+	struct device dev;
 	struct fasync_struct *async_queue;	/* fasync method */
 	spinlock_t lock;
 };
-- 
2.45.2

Re: [PATCH v3] pps: Fix a use-after-free

[Greg Kroah-Hartman]

On Mon, Nov 04, 2024 at 11:56:19PM -0800, Calvin Owens wrote:
> -	dev_info(pps->dev, "removed\n");
> +	dev_info(&pps->dev, "removed\n");

Nit, when drivers work properly,  they are quiet, no need for these
dev_info() calls.

>  static int pps_cdev_release(struct inode *inode, struct file *file)
>  {
> -	struct pps_device *pps = container_of(inode->i_cdev,
> -						struct pps_device, cdev);
> -	kobject_put(&pps->dev->kobj);
> +	struct pps_device *pps = file->private_data;
> +
> +	WARN_ON(pps->id != iminor(inode));

If this can happen, handle it and move on.  Don't just reboot the
machine if it's something that could be triggered (remember about
panic-on-warn systems.)

thanks,

greg k-h

Re: [PATCH v3] pps: Fix a use-after-free

[Calvin Owens]

On Tuesday 11/05 at 10:44 +0100, Greg Kroah-Hartman wrote:
> On Mon, Nov 04, 2024 at 11:56:19PM -0800, Calvin Owens wrote:
> > -	dev_info(pps->dev, "removed\n");
> > +	dev_info(&pps->dev, "removed\n");
> 
> Nit, when drivers work properly,  they are quiet, no need for these
> dev_info() calls.

I'll change these to dev_dbg().

> >  static int pps_cdev_release(struct inode *inode, struct file *file)
> >  {
> > -	struct pps_device *pps = container_of(inode->i_cdev,
> > -						struct pps_device, cdev);
> > -	kobject_put(&pps->dev->kobj);
> > +	struct pps_device *pps = file->private_data;
> > +
> > +	WARN_ON(pps->id != iminor(inode));
> 
> If this can happen, handle it and move on.  Don't just reboot the
> machine if it's something that could be triggered (remember about
> panic-on-warn systems.)

It's a fairly paranoid WARN(): it's a bug if it happens, and I don't
think it can happen. Should I remove it?

The test-robot found a couple *pps->dev dereferences I missed, I'll send
a v4 in the next day or two with those fixed as well.

Thanks,
Calvin

> thanks,
> 
> greg k-h

[PATCH v4] pps: Fix a use-after-free

[Calvin Owens]

On a board running ntpd and gpsd, I'm seeing a consistent use-after-free
in sys_exit() from gpsd when rebooting:

    pps pps1: removed
    ------------[ cut here ]------------
    kobject: '(null)' (00000000db4bec24): is not initialized, yet kobject_put() is being called.
    WARNING: CPU: 2 PID: 440 at lib/kobject.c:734 kobject_put+0x120/0x150
    CPU: 2 UID: 299 PID: 440 Comm: gpsd Not tainted 6.11.0-rc6-00308-gb31c44928842 #1
    Hardware name: Raspberry Pi 4 Model B Rev 1.1 (DT)
    pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
    pc : kobject_put+0x120/0x150
    lr : kobject_put+0x120/0x150
    sp : ffffffc0803d3ae0
    x29: ffffffc0803d3ae0 x28: ffffff8042dc9738 x27: 0000000000000001
    x26: 0000000000000000 x25: ffffff8042dc9040 x24: ffffff8042dc9440
    x23: ffffff80402a4620 x22: ffffff8042ef4bd0 x21: ffffff80405cb600
    x20: 000000000008001b x19: ffffff8040b3b6e0 x18: 0000000000000000
    x17: 0000000000000000 x16: 0000000000000000 x15: 696e6920746f6e20
    x14: 7369203a29343263 x13: 205d303434542020 x12: 0000000000000000
    x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000000
    x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
    x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000
    x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000000
    Call trace:
     kobject_put+0x120/0x150
     cdev_put+0x20/0x3c
     __fput+0x2c4/0x2d8
     ____fput+0x1c/0x38
     task_work_run+0x70/0xfc
     do_exit+0x2a0/0x924
     do_group_exit+0x34/0x90
     get_signal+0x7fc/0x8c0
     do_signal+0x128/0x13b4
     do_notify_resume+0xdc/0x160
     el0_svc+0xd4/0xf8
     el0t_64_sync_handler+0x140/0x14c
     el0t_64_sync+0x190/0x194
    ---[ end trace 0000000000000000 ]---

...followed by more symptoms of corruption, with similar stacks:

    refcount_t: underflow; use-after-free.
    kernel BUG at lib/list_debug.c:62!
    Kernel panic - not syncing: Oops - BUG: Fatal exception

This happens because pps_device_destruct() frees the pps_device with the
embedded cdev immediately after calling cdev_del(), but, as the comment
above cdev_del() notes, fops for previously opened cdevs are still
callable even after cdev_del() returns. I think this bug has always
been there: I can't explain why it suddenly started happening every time
I reboot this particular board.

In commit d953e0e837e6 ("pps: Fix a use-after free bug when
unregistering a source."), George Spelvin suggested removing the
embedded cdev. That seems like the simplest way to fix this, so I've
implemented his suggestion, using __register_chrdev() with pps_idr
becoming the source of truth for which minor corresponds to which
device.

But now that pps_idr defines userspace visibility instead of cdev_add(),
we need to be sure the pps->dev refcount can't reach zero while
userspace can still find it again. So, the idr_remove() call moves to
pps_unregister_cdev(), and pps_idr now holds a reference to pps->dev.

    pps_core: source serial1 got cdev (251:1)
    <...>
    pps pps1: removed
    pps_core: unregistering pps1
    pps_core: deallocating pps1

Fixes: d953e0e837e6 ("pps: Fix a use-after free bug when unregistering a source.")
Cc: stable@vger.kernel.org
Signed-off-by: Calvin Owens <calvin@wbinvd.org>
---
Changes in v4:
- Fix compile error in ptp_ocp
- Change five dev_info() calls to dev_dbg()
Changes in v3:
- Shorten patch title
- Embed the device struct in the pps struct
- Use foo_device(&pps->dev) instead of kobject_foo(&pps->dev.kobj)
Changes in v2:
- Don't move pr_debug() from pps_device_destruct() to pps_unregister_cdev()
- Actually add stable@vger.kernel.org to CC
---
 drivers/pps/clients/pps-gpio.c    |   4 +-
 drivers/pps/clients/pps-ktimer.c  |   4 +-
 drivers/pps/clients/pps-ldisc.c   |   6 +-
 drivers/pps/clients/pps_parport.c |   4 +-
 drivers/pps/kapi.c                |  10 +--
 drivers/pps/kc.c                  |  10 +--
 drivers/pps/pps.c                 | 127 ++++++++++++++++--------------
 drivers/ptp/ptp_ocp.c             |   2 +-
 include/linux/pps_kernel.h        |   3 +-
 9 files changed, 87 insertions(+), 83 deletions(-)

diff --git a/drivers/pps/clients/pps-gpio.c b/drivers/pps/clients/pps-gpio.c
index 791fdc9326dd..93e662912b53 100644
--- a/drivers/pps/clients/pps-gpio.c
+++ b/drivers/pps/clients/pps-gpio.c
@@ -214,8 +214,8 @@ static int pps_gpio_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}
 
-	dev_info(data->pps->dev, "Registered IRQ %d as PPS source\n",
-		 data->irq);
+	dev_dbg(&data->pps->dev, "Registered IRQ %d as PPS source\n",
+		data->irq);
 
 	return 0;
 }
diff --git a/drivers/pps/clients/pps-ktimer.c b/drivers/pps/clients/pps-ktimer.c
index d33106bd7a29..2f465549b843 100644
--- a/drivers/pps/clients/pps-ktimer.c
+++ b/drivers/pps/clients/pps-ktimer.c
@@ -56,7 +56,7 @@ static struct pps_source_info pps_ktimer_info = {
 
 static void __exit pps_ktimer_exit(void)
 {
-	dev_info(pps->dev, "ktimer PPS source unregistered\n");
+	dev_dbg(&pps->dev, "ktimer PPS source unregistered\n");
 
 	del_timer_sync(&ktimer);
 	pps_unregister_source(pps);
@@ -74,7 +74,7 @@ static int __init pps_ktimer_init(void)
 	timer_setup(&ktimer, pps_ktimer_event, 0);
 	mod_timer(&ktimer, jiffies + HZ);
 
-	dev_info(pps->dev, "ktimer PPS source registered\n");
+	dev_dbg(&pps->dev, "ktimer PPS source registered\n");
 
 	return 0;
 }
diff --git a/drivers/pps/clients/pps-ldisc.c b/drivers/pps/clients/pps-ldisc.c
index 443d6bae19d1..fa5660f3c4b7 100644
--- a/drivers/pps/clients/pps-ldisc.c
+++ b/drivers/pps/clients/pps-ldisc.c
@@ -32,7 +32,7 @@ static void pps_tty_dcd_change(struct tty_struct *tty, bool active)
 	pps_event(pps, &ts, active ? PPS_CAPTUREASSERT :
 			PPS_CAPTURECLEAR, NULL);
 
-	dev_dbg(pps->dev, "PPS %s at %lu\n",
+	dev_dbg(&pps->dev, "PPS %s at %lu\n",
 			active ? "assert" : "clear", jiffies);
 }
 
@@ -69,7 +69,7 @@ static int pps_tty_open(struct tty_struct *tty)
 		goto err_unregister;
 	}
 
-	dev_info(pps->dev, "source \"%s\" added\n", info.path);
+	dev_dbg(&pps->dev, "source \"%s\" added\n", info.path);
 
 	return 0;
 
@@ -89,7 +89,7 @@ static void pps_tty_close(struct tty_struct *tty)
 	if (WARN_ON(!pps))
 		return;
 
-	dev_info(pps->dev, "removed\n");
+	dev_info(&pps->dev, "removed\n");
 	pps_unregister_source(pps);
 }
 
diff --git a/drivers/pps/clients/pps_parport.c b/drivers/pps/clients/pps_parport.c
index abaffb4e1c1c..24db06750297 100644
--- a/drivers/pps/clients/pps_parport.c
+++ b/drivers/pps/clients/pps_parport.c
@@ -81,7 +81,7 @@ static void parport_irq(void *handle)
 	/* check the signal (no signal means the pulse is lost this time) */
 	if (!signal_is_set(port)) {
 		local_irq_restore(flags);
-		dev_err(dev->pps->dev, "lost the signal\n");
+		dev_err(&dev->pps->dev, "lost the signal\n");
 		goto out_assert;
 	}
 
@@ -98,7 +98,7 @@ static void parport_irq(void *handle)
 	/* timeout */
 	dev->cw_err++;
 	if (dev->cw_err >= CLEAR_WAIT_MAX_ERRORS) {
-		dev_err(dev->pps->dev, "disabled clear edge capture after %d"
+		dev_err(&dev->pps->dev, "disabled clear edge capture after %d"
 				" timeouts\n", dev->cw_err);
 		dev->cw = 0;
 		dev->cw_err = 0;
diff --git a/drivers/pps/kapi.c b/drivers/pps/kapi.c
index d9d566f70ed1..92d1b62ea239 100644
--- a/drivers/pps/kapi.c
+++ b/drivers/pps/kapi.c
@@ -41,7 +41,7 @@ static void pps_add_offset(struct pps_ktime *ts, struct pps_ktime *offset)
 static void pps_echo_client_default(struct pps_device *pps, int event,
 		void *data)
 {
-	dev_info(pps->dev, "echo %s %s\n",
+	dev_info(&pps->dev, "echo %s %s\n",
 		event & PPS_CAPTUREASSERT ? "assert" : "",
 		event & PPS_CAPTURECLEAR ? "clear" : "");
 }
@@ -112,7 +112,7 @@ struct pps_device *pps_register_source(struct pps_source_info *info,
 		goto kfree_pps;
 	}
 
-	dev_info(pps->dev, "new PPS source %s\n", info->name);
+	dev_dbg(&pps->dev, "new PPS source %s\n", info->name);
 
 	return pps;
 
@@ -166,7 +166,7 @@ void pps_event(struct pps_device *pps, struct pps_event_time *ts, int event,
 	/* check event type */
 	BUG_ON((event & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR)) == 0);
 
-	dev_dbg(pps->dev, "PPS event at %lld.%09ld\n",
+	dev_dbg(&pps->dev, "PPS event at %lld.%09ld\n",
 			(s64)ts->ts_real.tv_sec, ts->ts_real.tv_nsec);
 
 	timespec_to_pps_ktime(&ts_real, ts->ts_real);
@@ -188,7 +188,7 @@ void pps_event(struct pps_device *pps, struct pps_event_time *ts, int event,
 		/* Save the time stamp */
 		pps->assert_tu = ts_real;
 		pps->assert_sequence++;
-		dev_dbg(pps->dev, "capture assert seq #%u\n",
+		dev_dbg(&pps->dev, "capture assert seq #%u\n",
 			pps->assert_sequence);
 
 		captured = ~0;
@@ -202,7 +202,7 @@ void pps_event(struct pps_device *pps, struct pps_event_time *ts, int event,
 		/* Save the time stamp */
 		pps->clear_tu = ts_real;
 		pps->clear_sequence++;
-		dev_dbg(pps->dev, "capture clear seq #%u\n",
+		dev_dbg(&pps->dev, "capture clear seq #%u\n",
 			pps->clear_sequence);
 
 		captured = ~0;
diff --git a/drivers/pps/kc.c b/drivers/pps/kc.c
index 50dc59af45be..fbd23295afd7 100644
--- a/drivers/pps/kc.c
+++ b/drivers/pps/kc.c
@@ -43,11 +43,11 @@ int pps_kc_bind(struct pps_device *pps, struct pps_bind_args *bind_args)
 			pps_kc_hardpps_mode = 0;
 			pps_kc_hardpps_dev = NULL;
 			spin_unlock_irq(&pps_kc_hardpps_lock);
-			dev_info(pps->dev, "unbound kernel"
+			dev_info(&pps->dev, "unbound kernel"
 					" consumer\n");
 		} else {
 			spin_unlock_irq(&pps_kc_hardpps_lock);
-			dev_err(pps->dev, "selected kernel consumer"
+			dev_err(&pps->dev, "selected kernel consumer"
 					" is not bound\n");
 			return -EINVAL;
 		}
@@ -57,11 +57,11 @@ int pps_kc_bind(struct pps_device *pps, struct pps_bind_args *bind_args)
 			pps_kc_hardpps_mode = bind_args->edge;
 			pps_kc_hardpps_dev = pps;
 			spin_unlock_irq(&pps_kc_hardpps_lock);
-			dev_info(pps->dev, "bound kernel consumer: "
+			dev_info(&pps->dev, "bound kernel consumer: "
 				"edge=0x%x\n", bind_args->edge);
 		} else {
 			spin_unlock_irq(&pps_kc_hardpps_lock);
-			dev_err(pps->dev, "another kernel consumer"
+			dev_err(&pps->dev, "another kernel consumer"
 					" is already bound\n");
 			return -EINVAL;
 		}
@@ -83,7 +83,7 @@ void pps_kc_remove(struct pps_device *pps)
 		pps_kc_hardpps_mode = 0;
 		pps_kc_hardpps_dev = NULL;
 		spin_unlock_irq(&pps_kc_hardpps_lock);
-		dev_info(pps->dev, "unbound kernel consumer"
+		dev_info(&pps->dev, "unbound kernel consumer"
 				" on device removal\n");
 	} else
 		spin_unlock_irq(&pps_kc_hardpps_lock);
diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
index 25d47907db17..6a02245ea35f 100644
--- a/drivers/pps/pps.c
+++ b/drivers/pps/pps.c
@@ -25,7 +25,7 @@
  * Local variables
  */
 
-static dev_t pps_devt;
+static int pps_major;
 static struct class *pps_class;
 
 static DEFINE_MUTEX(pps_idr_lock);
@@ -62,7 +62,7 @@ static int pps_cdev_pps_fetch(struct pps_device *pps, struct pps_fdata *fdata)
 	else {
 		unsigned long ticks;
 
-		dev_dbg(pps->dev, "timeout %lld.%09d\n",
+		dev_dbg(&pps->dev, "timeout %lld.%09d\n",
 				(long long) fdata->timeout.sec,
 				fdata->timeout.nsec);
 		ticks = fdata->timeout.sec * HZ;
@@ -80,7 +80,7 @@ static int pps_cdev_pps_fetch(struct pps_device *pps, struct pps_fdata *fdata)
 
 	/* Check for pending signals */
 	if (err == -ERESTARTSYS) {
-		dev_dbg(pps->dev, "pending signal caught\n");
+		dev_dbg(&pps->dev, "pending signal caught\n");
 		return -EINTR;
 	}
 
@@ -98,7 +98,7 @@ static long pps_cdev_ioctl(struct file *file,
 
 	switch (cmd) {
 	case PPS_GETPARAMS:
-		dev_dbg(pps->dev, "PPS_GETPARAMS\n");
+		dev_dbg(&pps->dev, "PPS_GETPARAMS\n");
 
 		spin_lock_irq(&pps->lock);
 
@@ -114,7 +114,7 @@ static long pps_cdev_ioctl(struct file *file,
 		break;
 
 	case PPS_SETPARAMS:
-		dev_dbg(pps->dev, "PPS_SETPARAMS\n");
+		dev_dbg(&pps->dev, "PPS_SETPARAMS\n");
 
 		/* Check the capabilities */
 		if (!capable(CAP_SYS_TIME))
@@ -124,14 +124,14 @@ static long pps_cdev_ioctl(struct file *file,
 		if (err)
 			return -EFAULT;
 		if (!(params.mode & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR))) {
-			dev_dbg(pps->dev, "capture mode unspecified (%x)\n",
+			dev_dbg(&pps->dev, "capture mode unspecified (%x)\n",
 								params.mode);
 			return -EINVAL;
 		}
 
 		/* Check for supported capabilities */
 		if ((params.mode & ~pps->info.mode) != 0) {
-			dev_dbg(pps->dev, "unsupported capabilities (%x)\n",
+			dev_dbg(&pps->dev, "unsupported capabilities (%x)\n",
 								params.mode);
 			return -EINVAL;
 		}
@@ -144,7 +144,7 @@ static long pps_cdev_ioctl(struct file *file,
 		/* Restore the read only parameters */
 		if ((params.mode & (PPS_TSFMT_TSPEC | PPS_TSFMT_NTPFP)) == 0) {
 			/* section 3.3 of RFC 2783 interpreted */
-			dev_dbg(pps->dev, "time format unspecified (%x)\n",
+			dev_dbg(&pps->dev, "time format unspecified (%x)\n",
 								params.mode);
 			pps->params.mode |= PPS_TSFMT_TSPEC;
 		}
@@ -165,7 +165,7 @@ static long pps_cdev_ioctl(struct file *file,
 		break;
 
 	case PPS_GETCAP:
-		dev_dbg(pps->dev, "PPS_GETCAP\n");
+		dev_dbg(&pps->dev, "PPS_GETCAP\n");
 
 		err = put_user(pps->info.mode, iuarg);
 		if (err)
@@ -176,7 +176,7 @@ static long pps_cdev_ioctl(struct file *file,
 	case PPS_FETCH: {
 		struct pps_fdata fdata;
 
-		dev_dbg(pps->dev, "PPS_FETCH\n");
+		dev_dbg(&pps->dev, "PPS_FETCH\n");
 
 		err = copy_from_user(&fdata, uarg, sizeof(struct pps_fdata));
 		if (err)
@@ -206,7 +206,7 @@ static long pps_cdev_ioctl(struct file *file,
 	case PPS_KC_BIND: {
 		struct pps_bind_args bind_args;
 
-		dev_dbg(pps->dev, "PPS_KC_BIND\n");
+		dev_dbg(&pps->dev, "PPS_KC_BIND\n");
 
 		/* Check the capabilities */
 		if (!capable(CAP_SYS_TIME))
@@ -218,7 +218,7 @@ static long pps_cdev_ioctl(struct file *file,
 
 		/* Check for supported capabilities */
 		if ((bind_args.edge & ~pps->info.mode) != 0) {
-			dev_err(pps->dev, "unsupported capabilities (%x)\n",
+			dev_err(&pps->dev, "unsupported capabilities (%x)\n",
 					bind_args.edge);
 			return -EINVAL;
 		}
@@ -227,7 +227,7 @@ static long pps_cdev_ioctl(struct file *file,
 		if (bind_args.tsformat != PPS_TSFMT_TSPEC ||
 				(bind_args.edge & ~PPS_CAPTUREBOTH) != 0 ||
 				bind_args.consumer != PPS_KC_HARDPPS) {
-			dev_err(pps->dev, "invalid kernel consumer bind"
+			dev_err(&pps->dev, "invalid kernel consumer bind"
 					" parameters (%x)\n", bind_args.edge);
 			return -EINVAL;
 		}
@@ -259,7 +259,7 @@ static long pps_cdev_compat_ioctl(struct file *file,
 		struct pps_fdata fdata;
 		int err;
 
-		dev_dbg(pps->dev, "PPS_FETCH\n");
+		dev_dbg(&pps->dev, "PPS_FETCH\n");
 
 		err = copy_from_user(&compat, uarg, sizeof(struct pps_fdata_compat));
 		if (err)
@@ -296,20 +296,36 @@ static long pps_cdev_compat_ioctl(struct file *file,
 #define pps_cdev_compat_ioctl	NULL
 #endif
 
+static struct pps_device *pps_idr_get(unsigned long id)
+{
+	struct pps_device *pps;
+
+	mutex_lock(&pps_idr_lock);
+	pps = idr_find(&pps_idr, id);
+	if (pps)
+		get_device(&pps->dev);
+
+	mutex_unlock(&pps_idr_lock);
+	return pps;
+}
+
 static int pps_cdev_open(struct inode *inode, struct file *file)
 {
-	struct pps_device *pps = container_of(inode->i_cdev,
-						struct pps_device, cdev);
+	struct pps_device *pps = pps_idr_get(iminor(inode));
+
+	if (!pps)
+		return -ENODEV;
+
 	file->private_data = pps;
-	kobject_get(&pps->dev->kobj);
 	return 0;
 }
 
 static int pps_cdev_release(struct inode *inode, struct file *file)
 {
-	struct pps_device *pps = container_of(inode->i_cdev,
-						struct pps_device, cdev);
-	kobject_put(&pps->dev->kobj);
+	struct pps_device *pps = file->private_data;
+
+	WARN_ON(pps->id != iminor(inode));
+	put_device(&pps->dev);
 	return 0;
 }
 
@@ -331,22 +347,13 @@ 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);
-	idr_remove(&pps_idr, pps->id);
-	mutex_unlock(&pps_idr_lock);
-
-	kfree(dev);
 	kfree(pps);
 }
 
 int pps_register_cdev(struct pps_device *pps)
 {
 	int err;
-	dev_t devt;
 
 	mutex_lock(&pps_idr_lock);
 	/*
@@ -363,40 +370,29 @@ int pps_register_cdev(struct pps_device *pps)
 		goto out_unlock;
 	}
 	pps->id = err;
-	mutex_unlock(&pps_idr_lock);
-
-	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);
+	pps->dev.class = pps_class;
+	pps->dev.parent = pps->info.dev;
+	pps->dev.devt = MKDEV(pps_major, pps->id);
+	dev_set_drvdata(&pps->dev, pps);
+	dev_set_name(&pps->dev, "pps%d", pps->id);
+	err = device_register(&pps->dev);
+	if (err)
 		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;
-	}
 
 	/* Override the release function with our own */
-	pps->dev->release = pps_device_destruct;
+	pps->dev.release = pps_device_destruct;
 
-	pr_debug("source %s got cdev (%d:%d)\n", pps->info.name,
-			MAJOR(pps_devt), pps->id);
+	pr_debug("source %s got cdev (%d:%d)\n", pps->info.name, pps_major,
+		 pps->id);
 
+	get_device(&pps->dev);
+	mutex_unlock(&pps_idr_lock);
 	return 0;
 
-del_cdev:
-	cdev_del(&pps->cdev);
-
 free_idr:
-	mutex_lock(&pps_idr_lock);
 	idr_remove(&pps_idr, pps->id);
+	put_device(&pps->dev);
 out_unlock:
 	mutex_unlock(&pps_idr_lock);
 	return err;
@@ -406,7 +402,13 @@ void pps_unregister_cdev(struct pps_device *pps)
 {
 	pr_debug("unregistering pps%d\n", pps->id);
 	pps->lookup_cookie = NULL;
-	device_destroy(pps_class, pps->dev->devt);
+	device_destroy(pps_class, pps->dev.devt);
+
+	/* Now we can release the ID for re-use */
+	mutex_lock(&pps_idr_lock);
+	idr_remove(&pps_idr, pps->id);
+	put_device(&pps->dev);
+	mutex_unlock(&pps_idr_lock);
 }
 
 /*
@@ -426,6 +428,11 @@ void pps_unregister_cdev(struct pps_device *pps)
  * so that it will not be used again, even if the pps device cannot
  * be removed from the idr due to pending references holding the minor
  * number in use.
+ *
+ * Since pps_idr holds a reference to the device, the returned
+ * pps_device is guaranteed to be valid until pps_unregister_cdev() is
+ * called on it. But after calling pps_unregister_cdev(), it may be
+ * freed at any time.
  */
 struct pps_device *pps_lookup_dev(void const *cookie)
 {
@@ -448,13 +455,11 @@ EXPORT_SYMBOL(pps_lookup_dev);
 static void __exit pps_exit(void)
 {
 	class_destroy(pps_class);
-	unregister_chrdev_region(pps_devt, PPS_MAX_SOURCES);
+	__unregister_chrdev(pps_major, 0, PPS_MAX_SOURCES, "pps");
 }
 
 static int __init pps_init(void)
 {
-	int err;
-
 	pps_class = class_create("pps");
 	if (IS_ERR(pps_class)) {
 		pr_err("failed to allocate class\n");
@@ -462,8 +467,9 @@ static int __init pps_init(void)
 	}
 	pps_class->dev_groups = pps_groups;
 
-	err = alloc_chrdev_region(&pps_devt, 0, PPS_MAX_SOURCES, "pps");
-	if (err < 0) {
+	pps_major = __register_chrdev(0, 0, PPS_MAX_SOURCES, "pps",
+				      &pps_cdev_fops);
+	if (pps_major < 0) {
 		pr_err("failed to allocate char device region\n");
 		goto remove_class;
 	}
@@ -476,8 +482,7 @@ static int __init pps_init(void)
 
 remove_class:
 	class_destroy(pps_class);
-
-	return err;
+	return pps_major;
 }
 
 subsys_initcall(pps_init);
diff --git a/drivers/ptp/ptp_ocp.c b/drivers/ptp/ptp_ocp.c
index 5feecaadde8e..120db96d9e95 100644
--- a/drivers/ptp/ptp_ocp.c
+++ b/drivers/ptp/ptp_ocp.c
@@ -4420,7 +4420,7 @@ ptp_ocp_complete(struct ptp_ocp *bp)
 
 	pps = pps_lookup_dev(bp->ptp);
 	if (pps)
-		ptp_ocp_symlink(bp, pps->dev, "pps");
+		ptp_ocp_symlink(bp, &pps->dev, "pps");
 
 	ptp_ocp_debugfs_add_device(bp);
 
diff --git a/include/linux/pps_kernel.h b/include/linux/pps_kernel.h
index 78c8ac4951b5..c7abce28ed29 100644
--- a/include/linux/pps_kernel.h
+++ b/include/linux/pps_kernel.h
@@ -56,8 +56,7 @@ struct pps_device {
 
 	unsigned int id;			/* PPS source unique ID */
 	void const *lookup_cookie;		/* For pps_lookup_dev() only */
-	struct cdev cdev;
-	struct device *dev;
+	struct device dev;
 	struct fasync_struct *async_queue;	/* fasync method */
 	spinlock_t lock;
 };
-- 
2.45.2

Re: [PATCH v4] pps: Fix a use-after-free

[Michal Schmidt]

> On a board running ntpd and gpsd, I'm seeing a consistent use-after-free
> in sys_exit() from gpsd when rebooting:
> 
>     pps pps1: removed
>     ------------[ cut here ]------------
>     kobject: '(null)' (00000000db4bec24): is not initialized, yet kobject_put() is being called.
>     WARNING: CPU: 2 PID: 440 at lib/kobject.c:734 kobject_put+0x120/0x150
>     CPU: 2 UID: 299 PID: 440 Comm: gpsd Not tainted 6.11.0-rc6-00308-gb31c44928842 #1
>     Hardware name: Raspberry Pi 4 Model B Rev 1.1 (DT)
>     pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>     pc : kobject_put+0x120/0x150
>     lr : kobject_put+0x120/0x150
>     sp : ffffffc0803d3ae0
>     x29: ffffffc0803d3ae0 x28: ffffff8042dc9738 x27: 0000000000000001
>     x26: 0000000000000000 x25: ffffff8042dc9040 x24: ffffff8042dc9440
>     x23: ffffff80402a4620 x22: ffffff8042ef4bd0 x21: ffffff80405cb600
>     x20: 000000000008001b x19: ffffff8040b3b6e0 x18: 0000000000000000
>     x17: 0000000000000000 x16: 0000000000000000 x15: 696e6920746f6e20
>     x14: 7369203a29343263 x13: 205d303434542020 x12: 0000000000000000
>     x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000000
>     x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
>     x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000
>     x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000000
>     Call trace:
>      kobject_put+0x120/0x150
>      cdev_put+0x20/0x3c
>      __fput+0x2c4/0x2d8
>      ____fput+0x1c/0x38
>      task_work_run+0x70/0xfc
>      do_exit+0x2a0/0x924
>      do_group_exit+0x34/0x90
>      get_signal+0x7fc/0x8c0
>      do_signal+0x128/0x13b4
>      do_notify_resume+0xdc/0x160
>      el0_svc+0xd4/0xf8
>      el0t_64_sync_handler+0x140/0x14c
>      el0t_64_sync+0x190/0x194
>     ---[ end trace 0000000000000000 ]---
> 
> ...followed by more symptoms of corruption, with similar stacks:
> 
>     refcount_t: underflow; use-after-free.
>     kernel BUG at lib/list_debug.c:62!
>     Kernel panic - not syncing: Oops - BUG: Fatal exception
> 
> This happens because pps_device_destruct() frees the pps_device with the
> embedded cdev immediately after calling cdev_del(), but, as the comment
> above cdev_del() notes, fops for previously opened cdevs are still
> callable even after cdev_del() returns. I think this bug has always
> been there: I can't explain why it suddenly started happening every time
> I reboot this particular board.
> 
> In commit d953e0e837e6 ("pps: Fix a use-after free bug when
> unregistering a source."), George Spelvin suggested removing the
> embedded cdev. That seems like the simplest way to fix this, so I've
> implemented his suggestion, using __register_chrdev() with pps_idr
> becoming the source of truth for which minor corresponds to which
> device.
> 
> But now that pps_idr defines userspace visibility instead of cdev_add(),
> we need to be sure the pps->dev refcount can't reach zero while
> userspace can still find it again. So, the idr_remove() call moves to
> pps_unregister_cdev(), and pps_idr now holds a reference to pps->dev.
> 
>     pps_core: source serial1 got cdev (251:1)
>     <...>
>     pps pps1: removed
>     pps_core: unregistering pps1
>     pps_core: deallocating pps1
> 
> Fixes: d953e0e837e6 ("pps: Fix a use-after free bug when unregistering a source.")
> Cc: stable@vger.kernel.org
> Signed-off-by: Calvin Owens <calvin@wbinvd.org>

Reviewed-by: Michal Schmidt <mschmidt@redhat.com>

Re: [PATCH v3] pps: Fix a use-after-free

[kernel test robot]

Hi Calvin,

kernel test robot noticed the following build errors:

[auto build test ERROR on linus/master]
[also build test ERROR on v6.12-rc6 next-20241105]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Calvin-Owens/pps-Fix-a-use-after-free/20241105-155819
base:   linus/master
patch link:    https://lore.kernel.org/r/abc43b18f21379c21a4d2c63372a04b2746be665.1730792731.git.calvin%40wbinvd.org
patch subject: [PATCH v3] pps: Fix a use-after-free
config: i386-buildonly-randconfig-004-20241105 (https://download.01.org/0day-ci/archive/20241106/202411060043.hC5KjYAw-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241106/202411060043.hC5KjYAw-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202411060043.hC5KjYAw-lkp@intel.com/

All errors (new ones prefixed by >>):

   drivers/ptp/ptp_ocp.c: In function 'ptp_ocp_complete':
>> drivers/ptp/ptp_ocp.c:4423:40: error: incompatible type for argument 2 of 'ptp_ocp_symlink'
    4423 |                 ptp_ocp_symlink(bp, pps->dev, "pps");
         |                                     ~~~^~~~~
         |                                        |
         |                                        struct device
   drivers/ptp/ptp_ocp.c:4387:52: note: expected 'struct device *' but argument is of type 'struct device'
    4387 | ptp_ocp_symlink(struct ptp_ocp *bp, struct device *child, const char *link)
         |                                     ~~~~~~~~~~~~~~~^~~~~


vim +/ptp_ocp_symlink +4423 drivers/ptp/ptp_ocp.c

773bda96492153 Jonathan Lemon  2021-08-03  4411  
773bda96492153 Jonathan Lemon  2021-08-03  4412  static int
773bda96492153 Jonathan Lemon  2021-08-03  4413  ptp_ocp_complete(struct ptp_ocp *bp)
773bda96492153 Jonathan Lemon  2021-08-03  4414  {
773bda96492153 Jonathan Lemon  2021-08-03  4415  	struct pps_device *pps;
773bda96492153 Jonathan Lemon  2021-08-03  4416  	char buf[32];
d7875b4b078f7e Vadim Fedorenko 2024-08-29  4417  
773bda96492153 Jonathan Lemon  2021-08-03  4418  	sprintf(buf, "ptp%d", ptp_clock_index(bp->ptp));
773bda96492153 Jonathan Lemon  2021-08-03  4419  	ptp_ocp_link_child(bp, buf, "ptp");
773bda96492153 Jonathan Lemon  2021-08-03  4420  
773bda96492153 Jonathan Lemon  2021-08-03  4421  	pps = pps_lookup_dev(bp->ptp);
773bda96492153 Jonathan Lemon  2021-08-03  4422  	if (pps)
773bda96492153 Jonathan Lemon  2021-08-03 @4423  		ptp_ocp_symlink(bp, pps->dev, "pps");
773bda96492153 Jonathan Lemon  2021-08-03  4424  
f67bf662d2cffa Jonathan Lemon  2021-09-14  4425  	ptp_ocp_debugfs_add_device(bp);
f67bf662d2cffa Jonathan Lemon  2021-09-14  4426  
773bda96492153 Jonathan Lemon  2021-08-03  4427  	return 0;
773bda96492153 Jonathan Lemon  2021-08-03  4428  }
773bda96492153 Jonathan Lemon  2021-08-03  4429  

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v3] pps: Fix a use-after-free

[kernel test robot]

Hi Calvin,

kernel test robot noticed the following build errors:

[auto build test ERROR on linus/master]
[also build test ERROR on v6.12-rc6 next-20241105]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Calvin-Owens/pps-Fix-a-use-after-free/20241105-155819
base:   linus/master
patch link:    https://lore.kernel.org/r/abc43b18f21379c21a4d2c63372a04b2746be665.1730792731.git.calvin%40wbinvd.org
patch subject: [PATCH v3] pps: Fix a use-after-free
config: um-allmodconfig (https://download.01.org/0day-ci/archive/20241106/202411061205.AZijSWPc-lkp@intel.com/config)
compiler: clang version 20.0.0git (https://github.com/llvm/llvm-project 639a7ac648f1e50ccd2556e17d401c04f9cce625)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241106/202411061205.AZijSWPc-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202411061205.AZijSWPc-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from drivers/ptp/ptp_ocp.c:10:
   In file included from include/linux/pci.h:38:
   In file included from include/linux/interrupt.h:11:
   In file included from include/linux/hardirq.h:11:
   In file included from arch/um/include/asm/hardirq.h:5:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:14:
   In file included from arch/um/include/asm/io.h:24:
   include/asm-generic/io.h:548:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     548 |         val = __raw_readb(PCI_IOBASE + addr);
         |                           ~~~~~~~~~~ ^
   include/asm-generic/io.h:561:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     561 |         val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr));
         |                                                         ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/little_endian.h:37:51: note: expanded from macro '__le16_to_cpu'
      37 | #define __le16_to_cpu(x) ((__force __u16)(__le16)(x))
         |                                                   ^
   In file included from drivers/ptp/ptp_ocp.c:10:
   In file included from include/linux/pci.h:38:
   In file included from include/linux/interrupt.h:11:
   In file included from include/linux/hardirq.h:11:
   In file included from arch/um/include/asm/hardirq.h:5:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:14:
   In file included from arch/um/include/asm/io.h:24:
   include/asm-generic/io.h:574:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     574 |         val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
         |                                                         ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/little_endian.h:35:51: note: expanded from macro '__le32_to_cpu'
      35 | #define __le32_to_cpu(x) ((__force __u32)(__le32)(x))
         |                                                   ^
   In file included from drivers/ptp/ptp_ocp.c:10:
   In file included from include/linux/pci.h:38:
   In file included from include/linux/interrupt.h:11:
   In file included from include/linux/hardirq.h:11:
   In file included from arch/um/include/asm/hardirq.h:5:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:14:
   In file included from arch/um/include/asm/io.h:24:
   include/asm-generic/io.h:585:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     585 |         __raw_writeb(value, PCI_IOBASE + addr);
         |                             ~~~~~~~~~~ ^
   include/asm-generic/io.h:595:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     595 |         __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
         |                                                       ~~~~~~~~~~ ^
   include/asm-generic/io.h:605:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     605 |         __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
         |                                                       ~~~~~~~~~~ ^
   include/asm-generic/io.h:693:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     693 |         readsb(PCI_IOBASE + addr, buffer, count);
         |                ~~~~~~~~~~ ^
   include/asm-generic/io.h:701:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     701 |         readsw(PCI_IOBASE + addr, buffer, count);
         |                ~~~~~~~~~~ ^
   include/asm-generic/io.h:709:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     709 |         readsl(PCI_IOBASE + addr, buffer, count);
         |                ~~~~~~~~~~ ^
   include/asm-generic/io.h:718:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     718 |         writesb(PCI_IOBASE + addr, buffer, count);
         |                 ~~~~~~~~~~ ^
   include/asm-generic/io.h:727:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     727 |         writesw(PCI_IOBASE + addr, buffer, count);
         |                 ~~~~~~~~~~ ^
   include/asm-generic/io.h:736:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     736 |         writesl(PCI_IOBASE + addr, buffer, count);
         |                 ~~~~~~~~~~ ^
   In file included from drivers/ptp/ptp_ocp.c:10:
   In file included from include/linux/pci.h:1650:
   In file included from include/linux/dmapool.h:14:
   In file included from include/linux/scatterlist.h:8:
   In file included from include/linux/mm.h:2213:
   include/linux/vmstat.h:518:36: warning: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
     518 |         return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
         |                               ~~~~~~~~~~~ ^ ~~~
>> drivers/ptp/ptp_ocp.c:4423:23: error: passing 'struct device' to parameter of incompatible type 'struct device *'; take the address with &
    4423 |                 ptp_ocp_symlink(bp, pps->dev, "pps");
         |                                     ^~~~~~~~
         |                                     &
   drivers/ptp/ptp_ocp.c:4387:52: note: passing argument to parameter 'child' here
    4387 | ptp_ocp_symlink(struct ptp_ocp *bp, struct device *child, const char *link)
         |                                                    ^
   13 warnings and 1 error generated.


vim +4423 drivers/ptp/ptp_ocp.c

773bda96492153 Jonathan Lemon  2021-08-03  4411  
773bda96492153 Jonathan Lemon  2021-08-03  4412  static int
773bda96492153 Jonathan Lemon  2021-08-03  4413  ptp_ocp_complete(struct ptp_ocp *bp)
773bda96492153 Jonathan Lemon  2021-08-03  4414  {
773bda96492153 Jonathan Lemon  2021-08-03  4415  	struct pps_device *pps;
773bda96492153 Jonathan Lemon  2021-08-03  4416  	char buf[32];
d7875b4b078f7e Vadim Fedorenko 2024-08-29  4417  
773bda96492153 Jonathan Lemon  2021-08-03  4418  	sprintf(buf, "ptp%d", ptp_clock_index(bp->ptp));
773bda96492153 Jonathan Lemon  2021-08-03  4419  	ptp_ocp_link_child(bp, buf, "ptp");
773bda96492153 Jonathan Lemon  2021-08-03  4420  
773bda96492153 Jonathan Lemon  2021-08-03  4421  	pps = pps_lookup_dev(bp->ptp);
773bda96492153 Jonathan Lemon  2021-08-03  4422  	if (pps)
773bda96492153 Jonathan Lemon  2021-08-03 @4423  		ptp_ocp_symlink(bp, pps->dev, "pps");
773bda96492153 Jonathan Lemon  2021-08-03  4424  
f67bf662d2cffa Jonathan Lemon  2021-09-14  4425  	ptp_ocp_debugfs_add_device(bp);
f67bf662d2cffa Jonathan Lemon  2021-09-14  4426  
773bda96492153 Jonathan Lemon  2021-08-03  4427  	return 0;
773bda96492153 Jonathan Lemon  2021-08-03  4428  }
773bda96492153 Jonathan Lemon  2021-08-03  4429  

-- 
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https://github.com/intel/lkp-tests/wiki