uio: Prevent device destruction while fds are open

Prevent destruction of a uio_device while user space apps hold open
file descriptors to that device. Further, access to the 'info' member
of the struct uio_device is protected by spinlock. This is to ensure
stale pointers to data not under control of the UIO subsystem are not
dereferenced.

Signed-off-by: Hamish Martin <hamish.martin@alliedtelesis.co.nz>
Reviewed-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index 1883ce6..e8f4ac9 100644 (file)
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -270,7 +270,7 @@ static int uio_dev_add_attributes(struct uio_device *idev)
                if (!map_found) {
                        map_found = 1;
                        idev->map_dir = kobject_create_and_add("maps",
-                                                       &idev->dev->kobj);
+                                                       &idev->dev.kobj);
                        if (!idev->map_dir) {
                                ret = -ENOMEM;
                                goto err_map;
@@ -299,7 +299,7 @@ static int uio_dev_add_attributes(struct uio_device *idev)
                if (!portio_found) {
                        portio_found = 1;
                        idev->portio_dir = kobject_create_and_add("portio",
-                                                       &idev->dev->kobj);
+                                                       &idev->dev.kobj);
                        if (!idev->portio_dir) {
                                ret = -ENOMEM;
                                goto err_portio;
@@ -342,7 +342,7 @@ err_map_kobj:
                kobject_put(&map->kobj);
        }
        kobject_put(idev->map_dir);
-       dev_err(idev->dev, "error creating sysfs files (%d)\n", ret);
+       dev_err(&idev->dev, "error creating sysfs files (%d)\n", ret);
        return ret;
 }
 
@@ -379,7 +379,7 @@ static int uio_get_minor(struct uio_device *idev)
                idev->minor = retval;
                retval = 0;
        } else if (retval == -ENOSPC) {
-               dev_err(idev->dev, "too many uio devices\n");
+               dev_err(&idev->dev, "too many uio devices\n");
                retval = -EINVAL;
        }
        mutex_unlock(&minor_lock);
@@ -433,6 +433,7 @@ static int uio_open(struct inode *inode, struct file *filep)
        struct uio_device *idev;
        struct uio_listener *listener;
        int ret = 0;
+       unsigned long flags;
 
        mutex_lock(&minor_lock);
        idev = idr_find(&uio_idr, iminor(inode));
@@ -442,9 +443,11 @@ static int uio_open(struct inode *inode, struct file *filep)
                goto out;
        }
 
+       get_device(&idev->dev);
+
        if (!try_module_get(idev->owner)) {
                ret = -ENODEV;
-               goto out;
+               goto err_module_get;
        }
 
        listener = kmalloc(sizeof(*listener), GFP_KERNEL);
@@ -457,11 +460,13 @@ static int uio_open(struct inode *inode, struct file *filep)
        listener->event_count = atomic_read(&idev->event);
        filep->private_data = listener;
 
-       if (idev->info->open) {
+       spin_lock_irqsave(&idev->info_lock, flags);
+       if (idev->info && idev->info->open)
                ret = idev->info->open(idev->info, inode);
-               if (ret)
-                       goto err_infoopen;
-       }
+       spin_unlock_irqrestore(&idev->info_lock, flags);
+       if (ret)
+               goto err_infoopen;
+
        return 0;
 
 err_infoopen:
@@ -470,6 +475,9 @@ err_infoopen:
 err_alloc_listener:
        module_put(idev->owner);
 
+err_module_get:
+       put_device(&idev->dev);
+
 out:
        return ret;
 }
@@ -487,12 +495,16 @@ static int uio_release(struct inode *inode, struct file *filep)
        int ret = 0;
        struct uio_listener *listener = filep->private_data;
        struct uio_device *idev = listener->dev;
+       unsigned long flags;
 
-       if (idev->info->release)
+       spin_lock_irqsave(&idev->info_lock, flags);
+       if (idev->info && idev->info->release)
                ret = idev->info->release(idev->info, inode);
+       spin_unlock_irqrestore(&idev->info_lock, flags);
 
        module_put(idev->owner);
        kfree(listener);
+       put_device(&idev->dev);
        return ret;
 }
 
@@ -500,9 +512,16 @@ static __poll_t uio_poll(struct file *filep, poll_table *wait)
 {
        struct uio_listener *listener = filep->private_data;
        struct uio_device *idev = listener->dev;
+       __poll_t ret = 0;
+       unsigned long flags;
 
-       if (!idev->info->irq)
-               return -EIO;
+       spin_lock_irqsave(&idev->info_lock, flags);
+       if (!idev->info || !idev->info->irq)
+               ret = -EIO;
+       spin_unlock_irqrestore(&idev->info_lock, flags);
+
+       if (ret)
+               return ret;
 
        poll_wait(filep, &idev->wait, wait);
        if (listener->event_count != atomic_read(&idev->event))
@@ -516,11 +535,17 @@ static ssize_t uio_read(struct file *filep, char __user *buf,
        struct uio_listener *listener = filep->private_data;
        struct uio_device *idev = listener->dev;
        DECLARE_WAITQUEUE(wait, current);
-       ssize_t retval;
+       ssize_t retval = 0;
        s32 event_count;
+       unsigned long flags;
 
-       if (!idev->info->irq)
-               return -EIO;
+       spin_lock_irqsave(&idev->info_lock, flags);
+       if (!idev->info || !idev->info->irq)
+               retval = -EIO;
+       spin_unlock_irqrestore(&idev->info_lock, flags);
+
+       if (retval)
+               return retval;
 
        if (count != sizeof(s32))
                return -EINVAL;
@@ -567,8 +592,10 @@ static ssize_t uio_write(struct file *filep, const char __user *buf,
        struct uio_device *idev = listener->dev;
        ssize_t retval;
        s32 irq_on;
+       unsigned long flags;
 
-       if (!idev->info->irq) {
+       spin_lock_irqsave(&idev->info_lock, flags);
+       if (!idev->info || !idev->info->irq) {
                retval = -EIO;
                goto out;
        }
@@ -591,6 +618,7 @@ static ssize_t uio_write(struct file *filep, const char __user *buf,
        retval = idev->info->irqcontrol(idev->info, irq_on);
 
 out:
+       spin_unlock_irqrestore(&idev->info_lock, flags);
        return retval ? retval : sizeof(s32);
 }
 
@@ -803,6 +831,13 @@ static void release_uio_class(void)
        uio_major_cleanup();
 }
 
+static void uio_device_release(struct device *dev)
+{
+       struct uio_device *idev = dev_get_drvdata(dev);
+
+       kfree(idev);
+}
+
 /**
  * uio_register_device - register a new userspace IO device
  * @owner:     module that creates the new device
@@ -823,13 +858,14 @@ int __uio_register_device(struct module *owner,
 
        info->uio_dev = NULL;
 
-       idev = devm_kzalloc(parent, sizeof(*idev), GFP_KERNEL);
+       idev = kzalloc(sizeof(*idev), GFP_KERNEL);
        if (!idev) {
                return -ENOMEM;
        }
 
        idev->owner = owner;
        idev->info = info;
+       spin_lock_init(&idev->info_lock);
        init_waitqueue_head(&idev->wait);
        atomic_set(&idev->event, 0);
 
@@ -837,14 +873,19 @@ int __uio_register_device(struct module *owner,
        if (ret)
                return ret;
 
-       idev->dev = device_create(&uio_class, parent,
-                                 MKDEV(uio_major, idev->minor), idev,
-                                 "uio%d", idev->minor);
-       if (IS_ERR(idev->dev)) {
-               printk(KERN_ERR "UIO: device register failed\n");
-               ret = PTR_ERR(idev->dev);
+       idev->dev.devt = MKDEV(uio_major, idev->minor);
+       idev->dev.class = &uio_class;
+       idev->dev.parent = parent;
+       idev->dev.release = uio_device_release;
+       dev_set_drvdata(&idev->dev, idev);
+
+       ret = dev_set_name(&idev->dev, "uio%d", idev->minor);
+       if (ret)
+               goto err_device_create;
+
+       ret = device_register(&idev->dev);
+       if (ret)
                goto err_device_create;
-       }
 
        ret = uio_dev_add_attributes(idev);
        if (ret)
@@ -872,7 +913,7 @@ int __uio_register_device(struct module *owner,
 err_request_irq:
        uio_dev_del_attributes(idev);
 err_uio_dev_add_attributes:
-       device_destroy(&uio_class, MKDEV(uio_major, idev->minor));
+       device_unregister(&idev->dev);
 err_device_create:
        uio_free_minor(idev);
        return ret;
@@ -887,6 +928,7 @@ EXPORT_SYMBOL_GPL(__uio_register_device);
 void uio_unregister_device(struct uio_info *info)
 {
        struct uio_device *idev;
+       unsigned long flags;
 
        if (!info || !info->uio_dev)
                return;
@@ -900,7 +942,11 @@ void uio_unregister_device(struct uio_info *info)
        if (info->irq && info->irq != UIO_IRQ_CUSTOM)
                free_irq(info->irq, idev);
 
-       device_destroy(&uio_class, MKDEV(uio_major, idev->minor));
+       spin_lock_irqsave(&idev->info_lock, flags);
+       idev->info = NULL;
+       spin_unlock_irqrestore(&idev->info_lock, flags);
+
+       device_unregister(&idev->dev);
 
        return;
 }

diff --git a/include/linux/uio_driver.h b/include/linux/uio_driver.h
index 3c85c81..6c5f207 100644 (file)
--- a/include/linux/uio_driver.h
+++ b/include/linux/uio_driver.h
@@ -14,6 +14,7 @@
 #ifndef _UIO_DRIVER_H_
 #define _UIO_DRIVER_H_
 
+#include <linux/device.h>
 #include <linux/fs.h>
 #include <linux/interrupt.h>
 
@@ -68,12 +69,13 @@ struct uio_port {
 
 struct uio_device {
         struct module           *owner;
-        struct device           *dev;
+       struct device           dev;
         int                     minor;
         atomic_t                event;
         struct fasync_struct    *async_queue;
         wait_queue_head_t       wait;
         struct uio_info         *info;
+       spinlock_t              info_lock;
         struct kobject          *map_dir;
         struct kobject          *portio_dir;
 };