From a087ce704b802becbb4b0f2a20f2cb3f6911802e Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Wed, 27 Apr 2016 19:28:26 -0300 Subject: [PATCH] [media] media-device: dynamically allocate struct media_devnode struct media_devnode is currently embedded at struct media_device. While this works fine during normal usage, it leads to a race condition during devnode unregister. the problem is that drivers assume that, after calling media_device_unregister(), the struct that contains media_device can be freed. This is not true, as it can't be freed until userspace closes all opened /dev/media devnodes. In other words, if the media devnode is still open, and media_device gets freed, any call to an ioctl will make the core to try to access struct media_device, with will cause an use-after-free and even GPF. Fix this by dynamically allocating the struct media_devnode and only freeing it when it is safe. Signed-off-by: Mauro Carvalho Chehab Signed-off-by: Mauro Carvalho Chehab --- drivers/media/media-device.c | 44 ++++++++++++++++++-------- drivers/media/media-devnode.c | 7 +++- drivers/media/usb/au0828/au0828-core.c | 4 +-- drivers/media/usb/uvc/uvc_driver.c | 2 +- include/media/media-device.h | 5 +-- include/media/media-devnode.h | 13 +++++++- 6 files changed, 52 insertions(+), 23 deletions(-) diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c index a1cd50f331f1..e61fa66d95df 100644 --- a/drivers/media/media-device.c +++ b/drivers/media/media-device.c @@ -423,7 +423,7 @@ static long media_device_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) { struct media_devnode *devnode = media_devnode_data(filp); - struct media_device *dev = to_media_device(devnode); + struct media_device *dev = devnode->media_dev; long ret; mutex_lock(&dev->graph_mutex); @@ -495,7 +495,7 @@ static long media_device_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) { struct media_devnode *devnode = media_devnode_data(filp); - struct media_device *dev = to_media_device(devnode); + struct media_device *dev = devnode->media_dev; long ret; switch (cmd) { @@ -531,7 +531,8 @@ static const struct media_file_operations media_device_fops = { static ssize_t show_model(struct device *cd, struct device_attribute *attr, char *buf) { - struct media_device *mdev = to_media_device(to_media_devnode(cd)); + struct media_devnode *devnode = to_media_devnode(cd); + struct media_device *mdev = devnode->media_dev; return sprintf(buf, "%.*s\n", (int)sizeof(mdev->model), mdev->model); } @@ -704,23 +705,34 @@ EXPORT_SYMBOL_GPL(media_device_cleanup); int __must_check __media_device_register(struct media_device *mdev, struct module *owner) { + struct media_devnode *devnode; int ret; + devnode = kzalloc(sizeof(*devnode), GFP_KERNEL); + if (!devnode) + return -ENOMEM; + /* Register the device node. */ - mdev->devnode.fops = &media_device_fops; - mdev->devnode.parent = mdev->dev; - mdev->devnode.release = media_device_release; + mdev->devnode = devnode; + devnode->fops = &media_device_fops; + devnode->parent = mdev->dev; + devnode->release = media_device_release; /* 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) + ret = media_devnode_register(mdev, devnode, owner); + if (ret < 0) { + mdev->devnode = NULL; + kfree(devnode); return ret; + } - ret = device_create_file(&mdev->devnode.dev, &dev_attr_model); + ret = device_create_file(&devnode->dev, &dev_attr_model); if (ret < 0) { - media_devnode_unregister(&mdev->devnode); + mdev->devnode = NULL; + media_devnode_unregister(devnode); + kfree(devnode); return ret; } @@ -771,7 +783,7 @@ void media_device_unregister(struct media_device *mdev) mutex_lock(&mdev->graph_mutex); /* Check if mdev was ever registered at all */ - if (!media_devnode_is_registered(&mdev->devnode)) { + if (!media_devnode_is_registered(mdev->devnode)) { mutex_unlock(&mdev->graph_mutex); return; } @@ -794,9 +806,13 @@ void media_device_unregister(struct media_device *mdev) mutex_unlock(&mdev->graph_mutex); - device_remove_file(&mdev->devnode.dev, &dev_attr_model); - dev_dbg(mdev->dev, "Media device unregistering\n"); - media_devnode_unregister(&mdev->devnode); + dev_dbg(mdev->dev, "Media device unregistered\n"); + + /* Check if mdev devnode was registered */ + if (media_devnode_is_registered(mdev->devnode)) { + device_remove_file(&mdev->devnode->dev, &dev_attr_model); + media_devnode_unregister(mdev->devnode); + } } EXPORT_SYMBOL_GPL(media_device_unregister); diff --git a/drivers/media/media-devnode.c b/drivers/media/media-devnode.c index 7481c9610945..ecdc02d6ed83 100644 --- a/drivers/media/media-devnode.c +++ b/drivers/media/media-devnode.c @@ -44,6 +44,7 @@ #include #include +#include #define MEDIA_NUM_DEVICES 256 #define MEDIA_NAME "media" @@ -74,6 +75,8 @@ static void media_devnode_release(struct device *cd) /* Release media_devnode and perform other cleanups as needed. */ if (devnode->release) devnode->release(devnode); + + kfree(devnode); } static struct bus_type media_bus_type = { @@ -219,7 +222,8 @@ static const struct file_operations media_devnode_fops = { .llseek = no_llseek, }; -int __must_check media_devnode_register(struct media_devnode *devnode, +int __must_check media_devnode_register(struct media_device *mdev, + struct media_devnode *devnode, struct module *owner) { int minor; @@ -238,6 +242,7 @@ int __must_check media_devnode_register(struct media_devnode *devnode, mutex_unlock(&media_devnode_lock); devnode->minor = minor; + devnode->media_dev = mdev; /* Part 2: Initialize and register the character device */ cdev_init(&devnode->cdev, &media_devnode_fops); diff --git a/drivers/media/usb/au0828/au0828-core.c b/drivers/media/usb/au0828/au0828-core.c index 321ea5cf1329..bf53553d2624 100644 --- a/drivers/media/usb/au0828/au0828-core.c +++ b/drivers/media/usb/au0828/au0828-core.c @@ -142,7 +142,7 @@ static void au0828_unregister_media_device(struct au0828_dev *dev) struct media_device *mdev = dev->media_dev; struct media_entity_notify *notify, *nextp; - if (!mdev || !media_devnode_is_registered(&mdev->devnode)) + if (!mdev || !media_devnode_is_registered(mdev->devnode)) return; /* Remove au0828 entity_notify callbacks */ @@ -482,7 +482,7 @@ static int au0828_media_device_register(struct au0828_dev *dev, if (!dev->media_dev) return 0; - if (!media_devnode_is_registered(&dev->media_dev->devnode)) { + if (!media_devnode_is_registered(dev->media_dev->devnode)) { /* register media device */ ret = media_device_register(dev->media_dev); diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c index 451e84e962e2..302e284a95eb 100644 --- a/drivers/media/usb/uvc/uvc_driver.c +++ b/drivers/media/usb/uvc/uvc_driver.c @@ -1674,7 +1674,7 @@ static void uvc_delete(struct uvc_device *dev) if (dev->vdev.dev) v4l2_device_unregister(&dev->vdev); #ifdef CONFIG_MEDIA_CONTROLLER - if (media_devnode_is_registered(&dev->mdev.devnode)) + if (media_devnode_is_registered(dev->mdev.devnode)) media_device_unregister(&dev->mdev); media_device_cleanup(&dev->mdev); #endif diff --git a/include/media/media-device.h b/include/media/media-device.h index a9b33c47310d..f743ae2210ee 100644 --- a/include/media/media-device.h +++ b/include/media/media-device.h @@ -347,7 +347,7 @@ struct media_entity_notify { struct media_device { /* dev->driver_data points to this struct. */ struct device *dev; - struct media_devnode devnode; + struct media_devnode *devnode; char model[32]; char driver_name[32]; @@ -393,9 +393,6 @@ struct usb_device; #define MEDIA_DEV_NOTIFY_PRE_LINK_CH 0 #define MEDIA_DEV_NOTIFY_POST_LINK_CH 1 -/* media_devnode to media_device */ -#define to_media_device(node) container_of(node, struct media_device, devnode) - /** * media_entity_enum_init - Initialise an entity enumeration * diff --git a/include/media/media-devnode.h b/include/media/media-devnode.h index e1d5af077adb..5bb3b0e86d73 100644 --- a/include/media/media-devnode.h +++ b/include/media/media-devnode.h @@ -33,6 +33,8 @@ #include #include +struct media_device; + /* * Flag to mark the media_devnode struct as registered. Drivers must not touch * this flag directly, it will be set and cleared by media_devnode_register and @@ -81,6 +83,8 @@ struct media_file_operations { * before registering the node. */ struct media_devnode { + struct media_device *media_dev; + /* device ops */ const struct media_file_operations *fops; @@ -103,6 +107,7 @@ struct media_devnode { /** * media_devnode_register - register a media device node * + * @media_dev: struct media_device we want to register a device node * @devnode: media device node structure we want to register * @owner: should be filled with %THIS_MODULE * @@ -116,7 +121,8 @@ struct media_devnode { * the media_devnode structure is *not* called, so the caller is responsible for * freeing any data. */ -int __must_check media_devnode_register(struct media_devnode *devnode, +int __must_check media_devnode_register(struct media_device *mdev, + struct media_devnode *devnode, struct module *owner); /** @@ -146,9 +152,14 @@ static inline struct media_devnode *media_devnode_data(struct file *filp) * false otherwise. * * @devnode: pointer to struct &media_devnode. + * + * Note: If mdev is NULL, it also returns false. */ static inline int media_devnode_is_registered(struct media_devnode *devnode) { + if (!devnode) + return false; + return test_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); } -- 2.20.1