![Christian Brauner](/assets/img/avatar_default.png)
binderfs should not have a separate device_initcall(). When a kernel is compiled with CONFIG_ANDROID_BINDERFS register the filesystem alongside CONFIG_ANDROID_IPC. This use-case is especially sensible when users specify CONFIG_ANDROID_IPC=y, CONFIG_ANDROID_BINDERFS=y and ANDROID_BINDER_DEVICES="". When CONFIG_ANDROID_BINDERFS=n then this always succeeds so there's no regression potential for legacy workloads. Signed-off-by: Christian Brauner <christian@brauner.io> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
571 lines
14 KiB
C
571 lines
14 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#include <linux/compiler_types.h>
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#include <linux/errno.h>
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#include <linux/fs.h>
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#include <linux/fsnotify.h>
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#include <linux/gfp.h>
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#include <linux/idr.h>
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#include <linux/init.h>
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#include <linux/ipc_namespace.h>
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#include <linux/kdev_t.h>
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#include <linux/kernel.h>
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#include <linux/list.h>
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#include <linux/namei.h>
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#include <linux/magic.h>
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#include <linux/major.h>
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#include <linux/miscdevice.h>
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#include <linux/module.h>
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#include <linux/mutex.h>
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#include <linux/mount.h>
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#include <linux/parser.h>
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#include <linux/radix-tree.h>
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#include <linux/sched.h>
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#include <linux/seq_file.h>
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#include <linux/slab.h>
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#include <linux/spinlock_types.h>
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#include <linux/stddef.h>
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#include <linux/string.h>
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#include <linux/types.h>
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#include <linux/uaccess.h>
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#include <linux/user_namespace.h>
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#include <linux/xarray.h>
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#include <uapi/asm-generic/errno-base.h>
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#include <uapi/linux/android/binder.h>
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#include <uapi/linux/android/binderfs.h>
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#include "binder_internal.h"
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#define FIRST_INODE 1
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#define SECOND_INODE 2
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#define INODE_OFFSET 3
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#define INTSTRLEN 21
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#define BINDERFS_MAX_MINOR (1U << MINORBITS)
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/* Ensure that the initial ipc namespace always has devices available. */
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#define BINDERFS_MAX_MINOR_CAPPED (BINDERFS_MAX_MINOR - 4)
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static dev_t binderfs_dev;
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static DEFINE_MUTEX(binderfs_minors_mutex);
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static DEFINE_IDA(binderfs_minors);
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/**
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* binderfs_mount_opts - mount options for binderfs
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* @max: maximum number of allocatable binderfs binder devices
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*/
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struct binderfs_mount_opts {
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int max;
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};
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enum {
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Opt_max,
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Opt_err
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};
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static const match_table_t tokens = {
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{ Opt_max, "max=%d" },
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{ Opt_err, NULL }
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};
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/**
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* binderfs_info - information about a binderfs mount
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* @ipc_ns: The ipc namespace the binderfs mount belongs to.
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* @control_dentry: This records the dentry of this binderfs mount
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* binder-control device.
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* @root_uid: uid that needs to be used when a new binder device is
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* created.
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* @root_gid: gid that needs to be used when a new binder device is
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* created.
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* @mount_opts: The mount options in use.
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* @device_count: The current number of allocated binder devices.
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*/
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struct binderfs_info {
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struct ipc_namespace *ipc_ns;
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struct dentry *control_dentry;
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kuid_t root_uid;
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kgid_t root_gid;
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struct binderfs_mount_opts mount_opts;
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int device_count;
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};
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static inline struct binderfs_info *BINDERFS_I(const struct inode *inode)
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{
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return inode->i_sb->s_fs_info;
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}
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bool is_binderfs_device(const struct inode *inode)
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{
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if (inode->i_sb->s_magic == BINDERFS_SUPER_MAGIC)
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return true;
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return false;
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}
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/**
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* binderfs_binder_device_create - allocate inode from super block of a
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* binderfs mount
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* @ref_inode: inode from wich the super block will be taken
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* @userp: buffer to copy information about new device for userspace to
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* @req: struct binderfs_device as copied from userspace
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*
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* This function allocates a new binder_device and reserves a new minor
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* number for it.
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* Minor numbers are limited and tracked globally in binderfs_minors. The
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* function will stash a struct binder_device for the specific binder
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* device in i_private of the inode.
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* It will go on to allocate a new inode from the super block of the
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* filesystem mount, stash a struct binder_device in its i_private field
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* and attach a dentry to that inode.
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*
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* Return: 0 on success, negative errno on failure
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*/
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static int binderfs_binder_device_create(struct inode *ref_inode,
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struct binderfs_device __user *userp,
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struct binderfs_device *req)
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{
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int minor, ret;
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struct dentry *dentry, *root;
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struct binder_device *device;
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char *name = NULL;
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size_t name_len;
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struct inode *inode = NULL;
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struct super_block *sb = ref_inode->i_sb;
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struct binderfs_info *info = sb->s_fs_info;
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#if defined(CONFIG_IPC_NS)
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bool use_reserve = (info->ipc_ns == &init_ipc_ns);
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#else
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bool use_reserve = true;
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#endif
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/* Reserve new minor number for the new device. */
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mutex_lock(&binderfs_minors_mutex);
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if (++info->device_count <= info->mount_opts.max)
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minor = ida_alloc_max(&binderfs_minors,
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use_reserve ? BINDERFS_MAX_MINOR :
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BINDERFS_MAX_MINOR_CAPPED,
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GFP_KERNEL);
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else
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minor = -ENOSPC;
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if (minor < 0) {
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--info->device_count;
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mutex_unlock(&binderfs_minors_mutex);
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return minor;
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}
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mutex_unlock(&binderfs_minors_mutex);
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ret = -ENOMEM;
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device = kzalloc(sizeof(*device), GFP_KERNEL);
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if (!device)
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goto err;
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inode = new_inode(sb);
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if (!inode)
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goto err;
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inode->i_ino = minor + INODE_OFFSET;
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inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
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init_special_inode(inode, S_IFCHR | 0600,
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MKDEV(MAJOR(binderfs_dev), minor));
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inode->i_fop = &binder_fops;
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inode->i_uid = info->root_uid;
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inode->i_gid = info->root_gid;
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req->name[BINDERFS_MAX_NAME] = '\0'; /* NUL-terminate */
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name_len = strlen(req->name);
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/* Make sure to include terminating NUL byte */
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name = kmemdup(req->name, name_len + 1, GFP_KERNEL);
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if (!name)
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goto err;
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device->binderfs_inode = inode;
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device->context.binder_context_mgr_uid = INVALID_UID;
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device->context.name = name;
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device->miscdev.name = name;
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device->miscdev.minor = minor;
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mutex_init(&device->context.context_mgr_node_lock);
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req->major = MAJOR(binderfs_dev);
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req->minor = minor;
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ret = copy_to_user(userp, req, sizeof(*req));
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if (ret) {
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ret = -EFAULT;
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goto err;
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}
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root = sb->s_root;
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inode_lock(d_inode(root));
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/* look it up */
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dentry = lookup_one_len(name, root, name_len);
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if (IS_ERR(dentry)) {
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inode_unlock(d_inode(root));
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ret = PTR_ERR(dentry);
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goto err;
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}
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if (d_really_is_positive(dentry)) {
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/* already exists */
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dput(dentry);
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inode_unlock(d_inode(root));
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ret = -EEXIST;
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goto err;
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}
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inode->i_private = device;
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d_instantiate(dentry, inode);
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fsnotify_create(root->d_inode, dentry);
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inode_unlock(d_inode(root));
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return 0;
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err:
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kfree(name);
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kfree(device);
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mutex_lock(&binderfs_minors_mutex);
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--info->device_count;
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ida_free(&binderfs_minors, minor);
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mutex_unlock(&binderfs_minors_mutex);
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iput(inode);
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return ret;
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}
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/**
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* binderfs_ctl_ioctl - handle binder device node allocation requests
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*
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* The request handler for the binder-control device. All requests operate on
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* the binderfs mount the binder-control device resides in:
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* - BINDER_CTL_ADD
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* Allocate a new binder device.
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*
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* Return: 0 on success, negative errno on failure
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*/
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static long binder_ctl_ioctl(struct file *file, unsigned int cmd,
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unsigned long arg)
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{
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int ret = -EINVAL;
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struct inode *inode = file_inode(file);
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struct binderfs_device __user *device = (struct binderfs_device __user *)arg;
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struct binderfs_device device_req;
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switch (cmd) {
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case BINDER_CTL_ADD:
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ret = copy_from_user(&device_req, device, sizeof(device_req));
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if (ret) {
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ret = -EFAULT;
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break;
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}
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ret = binderfs_binder_device_create(inode, device, &device_req);
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break;
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default:
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break;
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}
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return ret;
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}
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static void binderfs_evict_inode(struct inode *inode)
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{
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struct binder_device *device = inode->i_private;
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struct binderfs_info *info = BINDERFS_I(inode);
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clear_inode(inode);
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if (!device)
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return;
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mutex_lock(&binderfs_minors_mutex);
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--info->device_count;
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ida_free(&binderfs_minors, device->miscdev.minor);
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mutex_unlock(&binderfs_minors_mutex);
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kfree(device->context.name);
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kfree(device);
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}
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/**
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* binderfs_parse_mount_opts - parse binderfs mount options
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* @data: options to set (can be NULL in which case defaults are used)
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*/
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static int binderfs_parse_mount_opts(char *data,
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struct binderfs_mount_opts *opts)
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{
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char *p;
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opts->max = BINDERFS_MAX_MINOR;
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while ((p = strsep(&data, ",")) != NULL) {
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substring_t args[MAX_OPT_ARGS];
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int token;
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int max_devices;
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if (!*p)
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continue;
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token = match_token(p, tokens, args);
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switch (token) {
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case Opt_max:
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if (match_int(&args[0], &max_devices) ||
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(max_devices < 0 ||
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(max_devices > BINDERFS_MAX_MINOR)))
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return -EINVAL;
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opts->max = max_devices;
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break;
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default:
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pr_err("Invalid mount options\n");
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return -EINVAL;
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}
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}
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return 0;
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}
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static int binderfs_remount(struct super_block *sb, int *flags, char *data)
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{
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struct binderfs_info *info = sb->s_fs_info;
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return binderfs_parse_mount_opts(data, &info->mount_opts);
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}
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static int binderfs_show_mount_opts(struct seq_file *seq, struct dentry *root)
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{
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struct binderfs_info *info;
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info = root->d_sb->s_fs_info;
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if (info->mount_opts.max <= BINDERFS_MAX_MINOR)
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seq_printf(seq, ",max=%d", info->mount_opts.max);
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return 0;
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}
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static const struct super_operations binderfs_super_ops = {
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.evict_inode = binderfs_evict_inode,
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.remount_fs = binderfs_remount,
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.show_options = binderfs_show_mount_opts,
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.statfs = simple_statfs,
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};
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static inline bool is_binderfs_control_device(const struct dentry *dentry)
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{
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struct binderfs_info *info = dentry->d_sb->s_fs_info;
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return info->control_dentry == dentry;
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}
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static int binderfs_rename(struct inode *old_dir, struct dentry *old_dentry,
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struct inode *new_dir, struct dentry *new_dentry,
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unsigned int flags)
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{
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if (is_binderfs_control_device(old_dentry) ||
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is_binderfs_control_device(new_dentry))
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return -EPERM;
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return simple_rename(old_dir, old_dentry, new_dir, new_dentry, flags);
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}
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static int binderfs_unlink(struct inode *dir, struct dentry *dentry)
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{
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if (is_binderfs_control_device(dentry))
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return -EPERM;
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return simple_unlink(dir, dentry);
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}
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static const struct file_operations binder_ctl_fops = {
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.owner = THIS_MODULE,
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.open = nonseekable_open,
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.unlocked_ioctl = binder_ctl_ioctl,
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.compat_ioctl = binder_ctl_ioctl,
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.llseek = noop_llseek,
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};
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/**
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* binderfs_binder_ctl_create - create a new binder-control device
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* @sb: super block of the binderfs mount
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*
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* This function creates a new binder-control device node in the binderfs mount
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* referred to by @sb.
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*
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* Return: 0 on success, negative errno on failure
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*/
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static int binderfs_binder_ctl_create(struct super_block *sb)
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{
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int minor, ret;
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struct dentry *dentry;
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struct binder_device *device;
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struct inode *inode = NULL;
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struct dentry *root = sb->s_root;
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struct binderfs_info *info = sb->s_fs_info;
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#if defined(CONFIG_IPC_NS)
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bool use_reserve = (info->ipc_ns == &init_ipc_ns);
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#else
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bool use_reserve = true;
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#endif
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device = kzalloc(sizeof(*device), GFP_KERNEL);
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if (!device)
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return -ENOMEM;
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/* If we have already created a binder-control node, return. */
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if (info->control_dentry) {
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ret = 0;
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goto out;
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}
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ret = -ENOMEM;
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inode = new_inode(sb);
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if (!inode)
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goto out;
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/* Reserve a new minor number for the new device. */
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mutex_lock(&binderfs_minors_mutex);
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minor = ida_alloc_max(&binderfs_minors,
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use_reserve ? BINDERFS_MAX_MINOR :
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BINDERFS_MAX_MINOR_CAPPED,
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GFP_KERNEL);
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mutex_unlock(&binderfs_minors_mutex);
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if (minor < 0) {
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ret = minor;
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goto out;
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}
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inode->i_ino = SECOND_INODE;
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inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
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init_special_inode(inode, S_IFCHR | 0600,
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MKDEV(MAJOR(binderfs_dev), minor));
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inode->i_fop = &binder_ctl_fops;
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inode->i_uid = info->root_uid;
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inode->i_gid = info->root_gid;
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device->binderfs_inode = inode;
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device->miscdev.minor = minor;
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dentry = d_alloc_name(root, "binder-control");
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if (!dentry)
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goto out;
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inode->i_private = device;
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info->control_dentry = dentry;
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d_add(dentry, inode);
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return 0;
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out:
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kfree(device);
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iput(inode);
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return ret;
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}
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static const struct inode_operations binderfs_dir_inode_operations = {
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.lookup = simple_lookup,
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.rename = binderfs_rename,
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.unlink = binderfs_unlink,
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};
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static int binderfs_fill_super(struct super_block *sb, void *data, int silent)
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{
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int ret;
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struct binderfs_info *info;
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struct inode *inode = NULL;
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sb->s_blocksize = PAGE_SIZE;
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sb->s_blocksize_bits = PAGE_SHIFT;
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/*
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* The binderfs filesystem can be mounted by userns root in a
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* non-initial userns. By default such mounts have the SB_I_NODEV flag
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* set in s_iflags to prevent security issues where userns root can
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* just create random device nodes via mknod() since it owns the
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* filesystem mount. But binderfs does not allow to create any files
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* including devices nodes. The only way to create binder devices nodes
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* is through the binder-control device which userns root is explicitly
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* allowed to do. So removing the SB_I_NODEV flag from s_iflags is both
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* necessary and safe.
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*/
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sb->s_iflags &= ~SB_I_NODEV;
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sb->s_iflags |= SB_I_NOEXEC;
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sb->s_magic = BINDERFS_SUPER_MAGIC;
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sb->s_op = &binderfs_super_ops;
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sb->s_time_gran = 1;
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sb->s_fs_info = kzalloc(sizeof(struct binderfs_info), GFP_KERNEL);
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if (!sb->s_fs_info)
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return -ENOMEM;
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info = sb->s_fs_info;
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info->ipc_ns = get_ipc_ns(current->nsproxy->ipc_ns);
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ret = binderfs_parse_mount_opts(data, &info->mount_opts);
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if (ret)
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return ret;
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info->root_gid = make_kgid(sb->s_user_ns, 0);
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if (!gid_valid(info->root_gid))
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info->root_gid = GLOBAL_ROOT_GID;
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info->root_uid = make_kuid(sb->s_user_ns, 0);
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if (!uid_valid(info->root_uid))
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info->root_uid = GLOBAL_ROOT_UID;
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inode = new_inode(sb);
|
|
if (!inode)
|
|
return -ENOMEM;
|
|
|
|
inode->i_ino = FIRST_INODE;
|
|
inode->i_fop = &simple_dir_operations;
|
|
inode->i_mode = S_IFDIR | 0755;
|
|
inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
|
|
inode->i_op = &binderfs_dir_inode_operations;
|
|
set_nlink(inode, 2);
|
|
|
|
sb->s_root = d_make_root(inode);
|
|
if (!sb->s_root)
|
|
return -ENOMEM;
|
|
|
|
return binderfs_binder_ctl_create(sb);
|
|
}
|
|
|
|
static struct dentry *binderfs_mount(struct file_system_type *fs_type,
|
|
int flags, const char *dev_name,
|
|
void *data)
|
|
{
|
|
return mount_nodev(fs_type, flags, data, binderfs_fill_super);
|
|
}
|
|
|
|
static void binderfs_kill_super(struct super_block *sb)
|
|
{
|
|
struct binderfs_info *info = sb->s_fs_info;
|
|
|
|
kill_litter_super(sb);
|
|
|
|
if (info && info->ipc_ns)
|
|
put_ipc_ns(info->ipc_ns);
|
|
|
|
kfree(info);
|
|
}
|
|
|
|
static struct file_system_type binder_fs_type = {
|
|
.name = "binder",
|
|
.mount = binderfs_mount,
|
|
.kill_sb = binderfs_kill_super,
|
|
.fs_flags = FS_USERNS_MOUNT,
|
|
};
|
|
|
|
int __init init_binderfs(void)
|
|
{
|
|
int ret;
|
|
|
|
/* Allocate new major number for binderfs. */
|
|
ret = alloc_chrdev_region(&binderfs_dev, 0, BINDERFS_MAX_MINOR,
|
|
"binder");
|
|
if (ret)
|
|
return ret;
|
|
|
|
ret = register_filesystem(&binder_fs_type);
|
|
if (ret) {
|
|
unregister_chrdev_region(binderfs_dev, BINDERFS_MAX_MINOR);
|
|
return ret;
|
|
}
|
|
|
|
return ret;
|
|
}
|