Add a new helper data structures media_devnode_compat_ref and
media_devnode_cdev. The latter is used to prevent user space from calling
IOCTLs or other system calls to the media device that has been already
unregistered and the former to help with obtaining the container struct
(either media_devnode_compat_ref or media_devnode) in media_open().
The media device's memory may of course still be released during the call
but there is only so much that can be done to this without the driver
managing the lifetime of the resources it needs somehow.
This patch should be reverted once all drivers have been converted to manage
their resources' lifetime.
Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
---
drivers/media/mc/mc-device.c | 55 ++++++++++----
drivers/media/mc/mc-devnode.c | 117 ++++++++++++++++++++++-------
drivers/media/v4l2-core/v4l2-dev.c | 28 +++++--
include/media/media-devnode.h | 64 +++++++++++++++-
4 files changed, 210 insertions(+), 54 deletions(-)
diff --git a/drivers/media/mc/mc-device.c b/drivers/media/mc/mc-device.c
index 9cc055deeec9..97d63146b344 100644
--- a/drivers/media/mc/mc-device.c
+++ b/drivers/media/mc/mc-device.c
@@ -55,6 +55,8 @@ static int media_device_open(struct media_devnode *devnode, struct file *filp)
if (!fh)
return -ENOMEM;
+ fh->fh.ref = devnode->ref;
+
filp->private_data = &fh->fh;
spin_lock_irqsave(&mdev->fh_list_lock, flags);
@@ -66,14 +68,19 @@ static int media_device_open(struct media_devnode *devnode, struct file *filp)
static int media_device_close(struct file *filp)
{
- struct media_devnode *devnode = media_devnode_data(filp);
- struct media_device *mdev = to_media_device(devnode);
- struct media_device_fh *fh = media_device_fh(filp);
- unsigned long flags;
+ struct media_device_fh *fh;
- spin_lock_irqsave(&mdev->fh_list_lock, flags);
- list_del(&fh->mdev_list);
- spin_unlock_irqrestore(&mdev->fh_list_lock, flags);
+ fh = media_device_fh(filp);
+
+ if (!fh->fh.ref || atomic_read(&fh->fh.ref->registered)) {
+ struct media_devnode *devnode = media_devnode_data(filp);
+ struct media_device *mdev = to_media_device(devnode);
+ unsigned long flags;
+
+ spin_lock_irqsave(&mdev->fh_list_lock, flags);
+ list_del(&fh->mdev_list);
+ spin_unlock_irqrestore(&mdev->fh_list_lock, flags);
+ }
kfree(fh);
@@ -812,28 +819,45 @@ EXPORT_SYMBOL_GPL(media_device_cleanup);
int __must_check __media_device_register(struct media_device *mdev,
struct module *owner)
{
+ struct media_devnode_compat_ref *ref = NULL;
int ret;
+ if (!mdev->ops || !mdev->ops->release) {
+ ref = kzalloc(sizeof(*mdev->devnode.ref), GFP_KERNEL);
+ if (!ref)
+ return -ENOMEM;
+ }
+
/* Register the device node. */
mdev->devnode.fops = &media_device_fops;
mdev->devnode.parent = mdev->dev;
+ mdev->devnode.ref = ref;
/* Set version 0 to indicate user-space that the graph is static */
mdev->topology_version = 0;
ret = media_devnode_register(&mdev->devnode, owner);
if (ret < 0)
- return ret;
+ goto out_put_ref;
+
+ ret = device_create_file(media_devnode_dev(&mdev->devnode),
+ &dev_attr_model);
+ if (ret < 0)
+ goto out_devnode_unregister;
- ret = device_create_file(&mdev->devnode.dev, &dev_attr_model);
- if (ret < 0) {
- media_devnode_unregister(&mdev->devnode);
- return ret;
- }
dev_dbg(mdev->dev, "Media device registered\n");
return 0;
+
+out_devnode_unregister:
+ media_devnode_unregister(&mdev->devnode);
+
+out_put_ref:
+ if (ref)
+ put_device(&ref->dev);
+
+ return ret;
}
EXPORT_SYMBOL_GPL(__media_device_register);
@@ -855,9 +879,12 @@ void media_device_unregister(struct media_device *mdev)
list_del_init(&mdev->fh_list);
spin_unlock_irqrestore(&mdev->fh_list_lock, flags);
- device_remove_file(&mdev->devnode.dev, &dev_attr_model);
+ device_remove_file(media_devnode_dev(&mdev->devnode), &dev_attr_model);
dev_dbg(mdev->dev, "Media device unregistering\n");
media_devnode_unregister(&mdev->devnode);
+
+ if (mdev->devnode.ref)
+ put_device(&mdev->devnode.ref->dev);
}
EXPORT_SYMBOL_GPL(media_device_unregister);
diff --git a/drivers/media/mc/mc-devnode.c b/drivers/media/mc/mc-devnode.c
index 0b5c24828e24..d64bb501a3ee 100644
--- a/drivers/media/mc/mc-devnode.c
+++ b/drivers/media/mc/mc-devnode.c
@@ -71,19 +71,45 @@ static void media_devnode_release(struct device *cd)
devnode->release(devnode);
}
+static void media_devnode_ref_release(struct device *cd)
+{
+ struct media_devnode_compat_ref *ref =
+ container_of_const(cd, struct media_devnode_compat_ref, dev);
+
+ media_devnode_free_minor(ref->minor);
+
+ kfree(ref);
+}
+
+struct media_devnode *to_media_devnode(struct device *dev)
+{
+ if (dev->release == media_devnode_release)
+ return container_of(dev, struct media_devnode, dev);
+
+ return container_of(dev, struct media_devnode_compat_ref, dev)->devnode;
+}
+
static struct bus_type media_bus_type = {
.name = MEDIA_NAME,
};
+static bool media_devnode_is_registered_compat(struct media_devnode_fh *fh)
+{
+ if (fh->ref)
+ return atomic_read(&fh->ref->registered);
+
+ return media_devnode_is_registered(fh->devnode);
+}
+
static ssize_t media_read(struct file *filp, char __user *buf,
size_t sz, loff_t *off)
{
struct media_devnode *devnode = media_devnode_data(filp);
+ if (!media_devnode_is_registered_compat(filp->private_data))
+ return -EIO;
if (!devnode->fops->read)
return -EINVAL;
- if (!media_devnode_is_registered(devnode))
- return -EIO;
return devnode->fops->read(filp, buf, sz, off);
}
@@ -92,10 +118,10 @@ static ssize_t media_write(struct file *filp, const char __user *buf,
{
struct media_devnode *devnode = media_devnode_data(filp);
+ if (!media_devnode_is_registered_compat(filp->private_data))
+ return -EIO;
if (!devnode->fops->write)
return -EINVAL;
- if (!media_devnode_is_registered(devnode))
- return -EIO;
return devnode->fops->write(filp, buf, sz, off);
}
@@ -104,7 +130,7 @@ static __poll_t media_poll(struct file *filp,
{
struct media_devnode *devnode = media_devnode_data(filp);
- if (!media_devnode_is_registered(devnode))
+ if (!media_devnode_is_registered_compat(filp->private_data))
return EPOLLERR | EPOLLHUP;
if (!devnode->fops->poll)
return DEFAULT_POLLMASK;
@@ -116,14 +142,9 @@ __media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg,
long (*ioctl_func)(struct file *filp, unsigned int cmd,
unsigned long arg))
{
- struct media_devnode *devnode = media_devnode_data(filp);
-
if (!ioctl_func)
return -ENOTTY;
- if (!media_devnode_is_registered(devnode))
- return -EIO;
-
return ioctl_func(filp, cmd, arg);
}
@@ -131,6 +152,9 @@ static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
struct media_devnode *devnode = media_devnode_data(filp);
+ if (!media_devnode_is_registered_compat(filp->private_data))
+ return -EIO;
+
return __media_ioctl(filp, cmd, arg, devnode->fops->ioctl);
}
@@ -141,6 +165,9 @@ static long media_compat_ioctl(struct file *filp, unsigned int cmd,
{
struct media_devnode *devnode = media_devnode_data(filp);
+ if (!media_devnode_is_registered_compat(filp->private_data))
+ return -EIO;
+
return __media_ioctl(filp, cmd, arg, devnode->fops->compat_ioctl);
}
@@ -149,6 +176,7 @@ static long media_compat_ioctl(struct file *filp, unsigned int cmd,
/* Override for the open function */
static int media_open(struct inode *inode, struct file *filp)
{
+ struct media_devnode_cdev *mcdev;
struct media_devnode *devnode;
struct media_devnode_fh *fh;
int ret;
@@ -160,7 +188,12 @@ static int media_open(struct inode *inode, struct file *filp)
* a crash.
*/
mutex_lock(&media_devnode_lock);
- devnode = container_of(inode->i_cdev, struct media_devnode, cdev);
+ mcdev = container_of(inode->i_cdev, struct media_devnode_cdev, cdev);
+ if (mcdev->is_compat_ref)
+ devnode = container_of(mcdev, struct media_devnode_compat_ref,
+ mcdev)->devnode;
+ else
+ devnode = container_of(mcdev, struct media_devnode, mcdev);
/* return ENXIO if the media device has been removed
already or if it is not registered anymore. */
if (!media_devnode_is_registered(devnode)) {
@@ -168,12 +201,12 @@ static int media_open(struct inode *inode, struct file *filp)
return -ENXIO;
}
/* and increase the device refcount */
- get_device(&devnode->dev);
+ get_device(media_devnode_dev(devnode));
mutex_unlock(&media_devnode_lock);
ret = devnode->fops->open(devnode, filp);
if (ret) {
- put_device(&devnode->dev);
+ put_device(media_devnode_dev(devnode));
return ret;
}
@@ -186,15 +219,21 @@ static int media_open(struct inode *inode, struct file *filp)
/* Override for the release function */
static int media_release(struct inode *inode, struct file *filp)
{
- struct media_devnode *devnode = media_devnode_data(filp);
-
- devnode->fops->release(filp);
+ struct media_devnode_fh *fh = filp->private_data;
+ struct device *dev;
+
+ if (!fh->ref) {
+ dev = &fh->devnode->dev;
+ fh->devnode->fops->release(filp);
+ } else {
+ dev = &fh->ref->dev;
+ fh->ref->release(filp);
+ }
filp->private_data = NULL;
- /* decrease the refcount unconditionally since the release()
- return value is ignored. */
- put_device(&devnode->dev);
+ put_device(dev);
+
return 0;
}
@@ -222,6 +261,9 @@ void media_devnode_init(struct media_devnode *devnode)
int __must_check media_devnode_register(struct media_devnode *devnode,
struct module *owner)
{
+ struct media_devnode_compat_ref *ref = devnode->ref;
+ struct cdev *cdev;
+ struct device *dev;
int minor;
int ret;
@@ -243,18 +285,31 @@ int __must_check media_devnode_register(struct media_devnode *devnode,
devnode->minor = minor;
/* Part 2: Initialize the media and character devices */
- cdev_init(&devnode->cdev, &media_devnode_fops);
- devnode->cdev.owner = owner;
- kobject_set_name(&devnode->cdev.kobj, "media%d", devnode->minor);
-
- devnode->dev.bus = &media_bus_type;
- devnode->dev.devt = MKDEV(MAJOR(media_dev_t), devnode->minor);
+ cdev = ref ? &ref->mcdev.cdev : &devnode->mcdev.cdev;
+ cdev_init(cdev, &media_devnode_fops);
+ cdev->owner = owner;
+ kobject_set_name(&cdev->kobj, "media%d", devnode->minor);
+
+ if (!ref) {
+ dev = &devnode->dev;
+ } else {
+ ref->mcdev.is_compat_ref = true;
+ device_initialize(&ref->dev);
+ atomic_set(&ref->registered, 1);
+ ref->devnode = devnode;
+ ref->minor = devnode->minor;
+ ref->release = devnode->fops->release;
+ dev = &ref->dev;
+ dev->release = media_devnode_ref_release;
+ }
+ dev->bus = &media_bus_type;
+ dev->devt = MKDEV(MAJOR(media_dev_t), devnode->minor);
if (devnode->parent)
- devnode->dev.parent = devnode->parent;
- dev_set_name(&devnode->dev, "media%d", devnode->minor);
+ dev->parent = devnode->parent;
+ dev_set_name(dev, "media%d", devnode->minor);
/* Part 3: Add the media and character devices */
- ret = cdev_device_add(&devnode->cdev, &devnode->dev);
+ ret = cdev_device_add(cdev, dev);
if (ret < 0) {
pr_err("%s: cdev_device_add failed\n", __func__);
goto cdev_add_error;
@@ -279,11 +334,15 @@ void media_devnode_unregister(struct media_devnode *devnode)
if (!media_devnode_is_registered(devnode))
return;
+ if (devnode->ref)
+ atomic_set(&devnode->ref->registered, 0);
+
mutex_lock(&media_devnode_lock);
clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
mutex_unlock(&media_devnode_lock);
- cdev_device_del(&devnode->cdev, &devnode->dev);
+ cdev_device_del(devnode->ref ? &devnode->ref->mcdev.cdev :
+ &devnode->mcdev.cdev, media_devnode_dev(devnode));
}
/*
diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
index c1e4995eaf5c..e18e7199ed83 100644
--- a/drivers/media/v4l2-core/v4l2-dev.c
+++ b/drivers/media/v4l2-core/v4l2-dev.c
@@ -179,7 +179,7 @@ static void v4l2_device_release(struct device *cd)
bool v4l2_dev_has_release = v4l2_dev->release;
#ifdef CONFIG_MEDIA_CONTROLLER
struct media_device *mdev = v4l2_dev->mdev;
- bool mdev_has_release = mdev && mdev->ops && mdev->ops->release;
+ bool mdev_has_ref = mdev && mdev->devnode.ref;
#endif
mutex_lock(&videodev_lock);
@@ -212,12 +212,24 @@ static void v4l2_device_release(struct device *cd)
}
#endif
- /* Release video_device and perform other
- cleanups as needed. */
+ /*
+ * Put struct media_devnode_compat_ref here as indicated by
+ * mdev_has_ref. mdev may be released by vdev->release() below.
+ */
+#ifdef CONFIG_MEDIA_CONTROLLER
+ if (mdev && mdev_has_ref)
+ media_device_put(mdev);
+#endif
+
+ /* Release video_device and perform other cleanups as needed. */
vdev->release(vdev);
#ifdef CONFIG_MEDIA_CONTROLLER
- if (mdev)
+ /*
+ * Put a reference to struct media_device acquired in
+ * video_register_media_controller().
+ */
+ if (mdev && !mdev_has_ref)
media_device_put(mdev);
/*
@@ -225,16 +237,18 @@ static void v4l2_device_release(struct device *cd)
* embedded in the same driver's context struct so having a release
* callback in both is a bug.
*/
- WARN_ON(v4l2_dev_has_release && mdev_has_release);
+ WARN_ON(v4l2_dev_has_release && !mdev_has_ref);
#endif
/*
* Decrease v4l2_device refcount, but only if the media device doesn't
- * have a release callback.
+ * have a release callback. Otherwise one could expect accessing
+ * released memory --- driver's context struct refcounted already via
+ * struct media_device.
*/
if (v4l2_dev_has_release
#ifdef CONFIG_MEDIA_CONTROLLER
- && !mdev_has_release
+ && mdev_has_ref
#endif
)
v4l2_device_put(v4l2_dev);
diff --git a/include/media/media-devnode.h b/include/media/media-devnode.h
index 840f7ae852d3..85d54e2c9a97 100644
--- a/include/media/media-devnode.h
+++ b/include/media/media-devnode.h
@@ -41,8 +41,6 @@ struct media_devnode;
* @compat_ioctl: pointer to the function that will handle 32 bits userspace
* calls to the ioctl() syscall on a Kernel compiled with 64 bits.
* @open: pointer to the function that implements open() syscall
- * @release: pointer to the function that will release the resources allocated
- * by the @open function.
*/
struct media_file_operations {
struct module *owner;
@@ -55,9 +53,56 @@ struct media_file_operations {
int (*release) (struct file *);
};
+/**
+ * struct media_devnode_cdev - Workaround for drivers not managing media device
+ * lifetime - character device
+ *
+ * Store the characeter device and whether this is a compatibility reference or
+ * not. struct media_devnode_cdev is embedded in either struct
+ * media_devnode_compat_ref or struct media_devnode.
+ *
+ * @cdev: the chracter device
+ * @is_compat_ref: Is this a compatibility reference or not?
+ */
+struct media_devnode_cdev {
+ struct cdev cdev;
+ bool is_compat_ref;
+};
+
+/**
+ * struct media_devnode_compat_ref - Workaround for drivers not managing media
+ * device lifetime - reference
+ *
+ * The purpose if this struct is to support drivers that do not manage the
+ * lifetime of their respective media devices to avoid the worst effects of
+ * this, namely an IOCTL call on an open file handle to a device that has been
+ * unbound causing a kernel oops systematically. This is not a fix. The proper,
+ * reliable way to handle this is to manage the resources used by the
+ * driver. This struct and its use can be removed once all drivers have been
+ * converted.
+ *
+ * @dev: struct device that remains in place as long as any reference remains
+ * @cdev: the related character device
+ * @devnode: a pointer back to the devnode
+ * @release: pointer to the function that will release the resources
+ * allocated by the @open function.
+ * @registered: is this device registered?
+ * @minor: the minor number of the media devnode
+ */
+struct media_devnode_compat_ref {
+ struct device dev;
+ struct media_devnode_cdev mcdev;
+ struct media_devnode *devnode;
+ int (*release)(struct file *);
+ atomic_t registered;
+ unsigned int minor;
+};
+
/**
* struct media_devnode_fh - Media device node file handle
* @devnode: pointer to the media device node
+ * @ref: media device compat ref, if the driver does not manage media
+ * device lifetime
*
* This structure serves as a base for per-file-handle data storage. Media
* device node users embed media_devnode_fh in their custom file handle data
@@ -67,6 +112,7 @@ struct media_file_operations {
*/
struct media_devnode_fh {
struct media_devnode *devnode;
+ struct media_devnode_compat_ref *ref;
};
/**
@@ -80,6 +126,8 @@ struct media_devnode_fh {
* @flags: flags, combination of the ``MEDIA_FLAG_*`` constants
* @release: release callback called at the end of ``media_devnode_release()``
* routine at media-device.c.
+ * @ref: reference for providing best effort memory safety in device
+ * removal
*
* This structure represents a media-related device node.
*
@@ -92,7 +140,7 @@ struct media_devnode {
/* sysfs */
struct device dev; /* media device */
- struct cdev cdev; /* character device */
+ struct media_devnode_cdev mcdev; /* character device + compat status */
struct device *parent; /* device parent */
/* device info */
@@ -101,10 +149,18 @@ struct media_devnode {
/* callbacks */
void (*release)(struct media_devnode *devnode);
+
+ /* compat reference */
+ struct media_devnode_compat_ref *ref;
};
+static inline struct device *media_devnode_dev(struct media_devnode *devnode)
+{
+ return devnode->ref ? &devnode->ref->dev : &devnode->dev;
+}
+
/* dev to media_devnode */
-#define to_media_devnode(cd) container_of(cd, struct media_devnode, dev)
+struct media_devnode *to_media_devnode(struct device *dev);
/**
* media_devnode_init - initialise a media devnode
--
2.39.2
