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-rw-r--r--drivers/android/binderfs.c564
1 files changed, 564 insertions, 0 deletions
diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c
new file mode 100644
index 000000000000..6a2185eb66c5
--- /dev/null
+++ b/drivers/android/binderfs.c
@@ -0,0 +1,564 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <linux/compiler_types.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/fsnotify.h>
+#include <linux/gfp.h>
+#include <linux/idr.h>
+#include <linux/init.h>
+#include <linux/ipc_namespace.h>
+#include <linux/kdev_t.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/namei.h>
+#include <linux/magic.h>
+#include <linux/major.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/mount.h>
+#include <linux/parser.h>
+#include <linux/radix-tree.h>
+#include <linux/sched.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+#include <linux/spinlock_types.h>
+#include <linux/stddef.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/uaccess.h>
+#include <linux/user_namespace.h>
+#include <linux/xarray.h>
+#include <uapi/asm-generic/errno-base.h>
+#include <uapi/linux/android/binder.h>
+#include <uapi/linux/android/binderfs.h>
+
+#include "binder_internal.h"
+
+#define FIRST_INODE 1
+#define SECOND_INODE 2
+#define INODE_OFFSET 3
+#define INTSTRLEN 21
+#define BINDERFS_MAX_MINOR (1U << MINORBITS)
+/* Ensure that the initial ipc namespace always has devices available. */
+#define BINDERFS_MAX_MINOR_CAPPED (BINDERFS_MAX_MINOR - 4)
+
+static dev_t binderfs_dev;
+static DEFINE_MUTEX(binderfs_minors_mutex);
+static DEFINE_IDA(binderfs_minors);
+
+/**
+ * binderfs_mount_opts - mount options for binderfs
+ * @max: maximum number of allocatable binderfs binder devices
+ */
+struct binderfs_mount_opts {
+ int max;
+};
+
+enum {
+ Opt_max,
+ Opt_err
+};
+
+static const match_table_t tokens = {
+ { Opt_max, "max=%d" },
+ { Opt_err, NULL }
+};
+
+/**
+ * binderfs_info - information about a binderfs mount
+ * @ipc_ns: The ipc namespace the binderfs mount belongs to.
+ * @control_dentry: This records the dentry of this binderfs mount
+ * binder-control device.
+ * @root_uid: uid that needs to be used when a new binder device is
+ * created.
+ * @root_gid: gid that needs to be used when a new binder device is
+ * created.
+ * @mount_opts: The mount options in use.
+ * @device_count: The current number of allocated binder devices.
+ */
+struct binderfs_info {
+ struct ipc_namespace *ipc_ns;
+ struct dentry *control_dentry;
+ kuid_t root_uid;
+ kgid_t root_gid;
+ struct binderfs_mount_opts mount_opts;
+ int device_count;
+};
+
+static inline struct binderfs_info *BINDERFS_I(const struct inode *inode)
+{
+ return inode->i_sb->s_fs_info;
+}
+
+bool is_binderfs_device(const struct inode *inode)
+{
+ if (inode->i_sb->s_magic == BINDERFS_SUPER_MAGIC)
+ return true;
+
+ return false;
+}
+
+/**
+ * binderfs_binder_device_create - allocate inode from super block of a
+ * binderfs mount
+ * @ref_inode: inode from wich the super block will be taken
+ * @userp: buffer to copy information about new device for userspace to
+ * @req: struct binderfs_device as copied from userspace
+ *
+ * This function allocates a new binder_device and reserves a new minor
+ * number for it.
+ * Minor numbers are limited and tracked globally in binderfs_minors. The
+ * function will stash a struct binder_device for the specific binder
+ * device in i_private of the inode.
+ * It will go on to allocate a new inode from the super block of the
+ * filesystem mount, stash a struct binder_device in its i_private field
+ * and attach a dentry to that inode.
+ *
+ * Return: 0 on success, negative errno on failure
+ */
+static int binderfs_binder_device_create(struct inode *ref_inode,
+ struct binderfs_device __user *userp,
+ struct binderfs_device *req)
+{
+ int minor, ret;
+ struct dentry *dentry, *root;
+ struct binder_device *device;
+ char *name = NULL;
+ size_t name_len;
+ struct inode *inode = NULL;
+ struct super_block *sb = ref_inode->i_sb;
+ struct binderfs_info *info = sb->s_fs_info;
+#if defined(CONFIG_IPC_NS)
+ bool use_reserve = (info->ipc_ns == &init_ipc_ns);
+#else
+ bool use_reserve = true;
+#endif
+
+ /* Reserve new minor number for the new device. */
+ mutex_lock(&binderfs_minors_mutex);
+ if (++info->device_count <= info->mount_opts.max)
+ minor = ida_alloc_max(&binderfs_minors,
+ use_reserve ? BINDERFS_MAX_MINOR :
+ BINDERFS_MAX_MINOR_CAPPED,
+ GFP_KERNEL);
+ else
+ minor = -ENOSPC;
+ if (minor < 0) {
+ --info->device_count;
+ mutex_unlock(&binderfs_minors_mutex);
+ return minor;
+ }
+ mutex_unlock(&binderfs_minors_mutex);
+
+ ret = -ENOMEM;
+ device = kzalloc(sizeof(*device), GFP_KERNEL);
+ if (!device)
+ goto err;
+
+ inode = new_inode(sb);
+ if (!inode)
+ goto err;
+
+ inode->i_ino = minor + INODE_OFFSET;
+ inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
+ init_special_inode(inode, S_IFCHR | 0600,
+ MKDEV(MAJOR(binderfs_dev), minor));
+ inode->i_fop = &binder_fops;
+ inode->i_uid = info->root_uid;
+ inode->i_gid = info->root_gid;
+
+ req->name[BINDERFS_MAX_NAME] = '\0'; /* NUL-terminate */
+ name_len = strlen(req->name);
+ /* Make sure to include terminating NUL byte */
+ name = kmemdup(req->name, name_len + 1, GFP_KERNEL);
+ if (!name)
+ goto err;
+
+ device->binderfs_inode = inode;
+ device->context.binder_context_mgr_uid = INVALID_UID;
+ device->context.name = name;
+ device->miscdev.name = name;
+ device->miscdev.minor = minor;
+ mutex_init(&device->context.context_mgr_node_lock);
+
+ req->major = MAJOR(binderfs_dev);
+ req->minor = minor;
+
+ ret = copy_to_user(userp, req, sizeof(*req));
+ if (ret) {
+ ret = -EFAULT;
+ goto err;
+ }
+
+ root = sb->s_root;
+ inode_lock(d_inode(root));
+
+ /* look it up */
+ dentry = lookup_one_len(name, root, name_len);
+ if (IS_ERR(dentry)) {
+ inode_unlock(d_inode(root));
+ ret = PTR_ERR(dentry);
+ goto err;
+ }
+
+ if (d_really_is_positive(dentry)) {
+ /* already exists */
+ dput(dentry);
+ inode_unlock(d_inode(root));
+ ret = -EEXIST;
+ goto err;
+ }
+
+ inode->i_private = device;
+ d_instantiate(dentry, inode);
+ fsnotify_create(root->d_inode, dentry);
+ inode_unlock(d_inode(root));
+
+ return 0;
+
+err:
+ kfree(name);
+ kfree(device);
+ mutex_lock(&binderfs_minors_mutex);
+ --info->device_count;
+ ida_free(&binderfs_minors, minor);
+ mutex_unlock(&binderfs_minors_mutex);
+ iput(inode);
+
+ return ret;
+}
+
+/**
+ * binderfs_ctl_ioctl - handle binder device node allocation requests
+ *
+ * The request handler for the binder-control device. All requests operate on
+ * the binderfs mount the binder-control device resides in:
+ * - BINDER_CTL_ADD
+ * Allocate a new binder device.
+ *
+ * Return: 0 on success, negative errno on failure
+ */
+static long binder_ctl_ioctl(struct file *file, unsigned int cmd,
+ unsigned long arg)
+{
+ int ret = -EINVAL;
+ struct inode *inode = file_inode(file);
+ struct binderfs_device __user *device = (struct binderfs_device __user *)arg;
+ struct binderfs_device device_req;
+
+ switch (cmd) {
+ case BINDER_CTL_ADD:
+ ret = copy_from_user(&device_req, device, sizeof(device_req));
+ if (ret) {
+ ret = -EFAULT;
+ break;
+ }
+
+ ret = binderfs_binder_device_create(inode, device, &device_req);
+ break;
+ default:
+ break;
+ }
+
+ return ret;
+}
+
+static void binderfs_evict_inode(struct inode *inode)
+{
+ struct binder_device *device = inode->i_private;
+ struct binderfs_info *info = BINDERFS_I(inode);
+
+ clear_inode(inode);
+
+ if (!device)
+ return;
+
+ mutex_lock(&binderfs_minors_mutex);
+ --info->device_count;
+ ida_free(&binderfs_minors, device->miscdev.minor);
+ mutex_unlock(&binderfs_minors_mutex);
+
+ kfree(device->context.name);
+ kfree(device);
+}
+
+/**
+ * binderfs_parse_mount_opts - parse binderfs mount options
+ * @data: options to set (can be NULL in which case defaults are used)
+ */
+static int binderfs_parse_mount_opts(char *data,
+ struct binderfs_mount_opts *opts)
+{
+ char *p;
+ opts->max = BINDERFS_MAX_MINOR;
+
+ while ((p = strsep(&data, ",")) != NULL) {
+ substring_t args[MAX_OPT_ARGS];
+ int token;
+ int max_devices;
+
+ if (!*p)
+ continue;
+
+ token = match_token(p, tokens, args);
+ switch (token) {
+ case Opt_max:
+ if (match_int(&args[0], &max_devices) ||
+ (max_devices < 0 ||
+ (max_devices > BINDERFS_MAX_MINOR)))
+ return -EINVAL;
+
+ opts->max = max_devices;
+ break;
+ default:
+ pr_err("Invalid mount options\n");
+ return -EINVAL;
+ }
+ }
+
+ return 0;
+}
+
+static int binderfs_remount(struct super_block *sb, int *flags, char *data)
+{
+ struct binderfs_info *info = sb->s_fs_info;
+ return binderfs_parse_mount_opts(data, &info->mount_opts);
+}
+
+static int binderfs_show_mount_opts(struct seq_file *seq, struct dentry *root)
+{
+ struct binderfs_info *info;
+
+ info = root->d_sb->s_fs_info;
+ if (info->mount_opts.max <= BINDERFS_MAX_MINOR)
+ seq_printf(seq, ",max=%d", info->mount_opts.max);
+
+ return 0;
+}
+
+static const struct super_operations binderfs_super_ops = {
+ .evict_inode = binderfs_evict_inode,
+ .remount_fs = binderfs_remount,
+ .show_options = binderfs_show_mount_opts,
+ .statfs = simple_statfs,
+};
+
+static inline bool is_binderfs_control_device(const struct dentry *dentry)
+{
+ struct binderfs_info *info = dentry->d_sb->s_fs_info;
+ return info->control_dentry == dentry;
+}
+
+static int binderfs_rename(struct inode *old_dir, struct dentry *old_dentry,
+ struct inode *new_dir, struct dentry *new_dentry,
+ unsigned int flags)
+{
+ if (is_binderfs_control_device(old_dentry) ||
+ is_binderfs_control_device(new_dentry))
+ return -EPERM;
+
+ return simple_rename(old_dir, old_dentry, new_dir, new_dentry, flags);
+}
+
+static int binderfs_unlink(struct inode *dir, struct dentry *dentry)
+{
+ if (is_binderfs_control_device(dentry))
+ return -EPERM;
+
+ return simple_unlink(dir, dentry);
+}
+
+static const struct file_operations binder_ctl_fops = {
+ .owner = THIS_MODULE,
+ .open = nonseekable_open,
+ .unlocked_ioctl = binder_ctl_ioctl,
+ .compat_ioctl = binder_ctl_ioctl,
+ .llseek = noop_llseek,
+};
+
+/**
+ * binderfs_binder_ctl_create - create a new binder-control device
+ * @sb: super block of the binderfs mount
+ *
+ * This function creates a new binder-control device node in the binderfs mount
+ * referred to by @sb.
+ *
+ * Return: 0 on success, negative errno on failure
+ */
+static int binderfs_binder_ctl_create(struct super_block *sb)
+{
+ int minor, ret;
+ struct dentry *dentry;
+ struct binder_device *device;
+ struct inode *inode = NULL;
+ struct dentry *root = sb->s_root;
+ struct binderfs_info *info = sb->s_fs_info;
+
+ device = kzalloc(sizeof(*device), GFP_KERNEL);
+ if (!device)
+ return -ENOMEM;
+
+ /* If we have already created a binder-control node, return. */
+ if (info->control_dentry) {
+ ret = 0;
+ goto out;
+ }
+
+ ret = -ENOMEM;
+ inode = new_inode(sb);
+ if (!inode)
+ goto out;
+
+ /* Reserve a new minor number for the new device. */
+ mutex_lock(&binderfs_minors_mutex);
+ minor = ida_alloc_max(&binderfs_minors, BINDERFS_MAX_MINOR, GFP_KERNEL);
+ mutex_unlock(&binderfs_minors_mutex);
+ if (minor < 0) {
+ ret = minor;
+ goto out;
+ }
+
+ inode->i_ino = SECOND_INODE;
+ inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
+ init_special_inode(inode, S_IFCHR | 0600,
+ MKDEV(MAJOR(binderfs_dev), minor));
+ inode->i_fop = &binder_ctl_fops;
+ inode->i_uid = info->root_uid;
+ inode->i_gid = info->root_gid;
+
+ device->binderfs_inode = inode;
+ device->miscdev.minor = minor;
+
+ dentry = d_alloc_name(root, "binder-control");
+ if (!dentry)
+ goto out;
+
+ inode->i_private = device;
+ info->control_dentry = dentry;
+ d_add(dentry, inode);
+
+ return 0;
+
+out:
+ kfree(device);
+ iput(inode);
+
+ return ret;
+}
+
+static const struct inode_operations binderfs_dir_inode_operations = {
+ .lookup = simple_lookup,
+ .rename = binderfs_rename,
+ .unlink = binderfs_unlink,
+};
+
+static int binderfs_fill_super(struct super_block *sb, void *data, int silent)
+{
+ int ret;
+ struct binderfs_info *info;
+ struct inode *inode = NULL;
+
+ sb->s_blocksize = PAGE_SIZE;
+ sb->s_blocksize_bits = PAGE_SHIFT;
+
+ /*
+ * The binderfs filesystem can be mounted by userns root in a
+ * non-initial userns. By default such mounts have the SB_I_NODEV flag
+ * set in s_iflags to prevent security issues where userns root can
+ * just create random device nodes via mknod() since it owns the
+ * filesystem mount. But binderfs does not allow to create any files
+ * including devices nodes. The only way to create binder devices nodes
+ * is through the binder-control device which userns root is explicitly
+ * allowed to do. So removing the SB_I_NODEV flag from s_iflags is both
+ * necessary and safe.
+ */
+ sb->s_iflags &= ~SB_I_NODEV;
+ sb->s_iflags |= SB_I_NOEXEC;
+ sb->s_magic = BINDERFS_SUPER_MAGIC;
+ sb->s_op = &binderfs_super_ops;
+ sb->s_time_gran = 1;
+
+ sb->s_fs_info = kzalloc(sizeof(struct binderfs_info), GFP_KERNEL);
+ if (!sb->s_fs_info)
+ return -ENOMEM;
+ info = sb->s_fs_info;
+
+ info->ipc_ns = get_ipc_ns(current->nsproxy->ipc_ns);
+
+ ret = binderfs_parse_mount_opts(data, &info->mount_opts);
+ if (ret)
+ return ret;
+
+ info->root_gid = make_kgid(sb->s_user_ns, 0);
+ if (!gid_valid(info->root_gid))
+ info->root_gid = GLOBAL_ROOT_GID;
+ info->root_uid = make_kuid(sb->s_user_ns, 0);
+ if (!uid_valid(info->root_uid))
+ info->root_uid = GLOBAL_ROOT_UID;
+
+ 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,
+};
+
+static 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;
+}
+
+device_initcall(init_binderfs);
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