[PATCH 2/2] uio: Fix uio driver to refcount device

Brian Russell
2015-03-19T17:55:47Z

Protect uio driver from its owner being unplugged while there are open fds.
Embed struct device in struct uio_device, use refcounting on device, free
uio_device on release.
info struct passed in uio_register_device can be freed on unregister, so null
out the field in uio_unregister_device and check accesses.

Signed-off-by: Brian Russell <brussell@brocade.com>
---
drivers/uio/uio.c | 58 +++++++++++++++++++++++++++++++---------------
include/linux/uio_driver.h | 2 +-
2 files changed, 40 insertions(+), 20 deletions(-)

diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index 65bf067..4629421 100644
--- 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)
goto err_map;
}
@@ -295,7 +295,7 @@ 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)
goto err_portio;
}
@@ -334,7 +334,7 @@ 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;
}

@@ -371,7 +371,7 @@ 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);
@@ -434,9 +434,11 @@ 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);
@@ -462,6 +464,9 @@ err_infoopen:
err_alloc_listener:
module_put(idev->owner);

+ err_module_get:
+ put_device(&idev->dev);
+
out:
return ret;
}
@@ -480,11 +485,12 @@ static int uio_release(struct inode *inode, struct file
*filep)
struct uio_listener *listener = filep->private_data;
struct uio_device *idev = listener->dev;

- if (idev->info->release)
+ if (idev->info && idev->info->release)
ret = idev->info->release(idev->info, inode);

module_put(idev->owner);
kfree(listener);
+ put_device(&idev->dev);
return ret;
}

@@ -493,7 +499,7 @@ static unsigned int uio_poll(struct file *filep, poll_table
*wait)
struct uio_listener *listener = filep->private_data;
struct uio_device *idev = listener->dev;

- if (!idev->info->irq)
+ if (!idev->info || !idev->info->irq)
return -EIO;

poll_wait(filep, &idev->wait, wait);
@@ -511,7 +517,7 @@ static ssize_t uio_read(struct file *filep, char __user *buf,
ssize_t retval;
s32 event_count;

- if (!idev->info->irq)
+ if (!idev->info || !idev->info->irq)
return -EIO;

if (count != sizeof(s32))
@@ -559,7 +565,7 @@ static ssize_t uio_write(struct file *filep, const char
__user *buf,
ssize_t retval;
s32 irq_on;

- if (!idev->info->irq)
+ if (!idev->info || !idev->info->irq)
return -EIO;

if (count != sizeof(s32))
@@ -785,6 +791,13 @@ 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
@@ -805,7 +818,7 @@ 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;
}
@@ -819,14 +832,19 @@ 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)
@@ -854,7 +872,7 @@ 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;
@@ -881,7 +899,9 @@ void uio_unregister_device(struct uio_info *info)

free_irq(idev->info->irq, idev);

- device_destroy(&uio_class, MKDEV(uio_major, idev->minor));
+ idev->info = NULL;
+
+ device_unregister(&idev->dev);

return;
}
diff --git a/include/linux/uio_driver.h b/include/linux/uio_driver.h
index 32c0e83..a11feeb 100644
--- a/include/linux/uio_driver.h
+++ b/include/linux/uio_driver.h
@@ -65,7 +65,7 @@ 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;
--
2.1.4