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1// SPDX-License-Identifier: GPL-2.02 3#include <linux/compiler_types.h>4#include <linux/errno.h>5#include <linux/fs.h>6#include <linux/fsnotify.h>7#include <linux/gfp.h>8#include <linux/idr.h>9#include <linux/init.h>10#include <linux/ipc_namespace.h>11#include <linux/kdev_t.h>12#include <linux/kernel.h>13#include <linux/list.h>14#include <linux/namei.h>15#include <linux/magic.h>16#include <linux/major.h>17#include <linux/miscdevice.h>18#include <linux/module.h>19#include <linux/mutex.h>20#include <linux/mount.h>21#include <linux/fs_parser.h>22#include <linux/sched.h>23#include <linux/seq_file.h>24#include <linux/slab.h>25#include <linux/spinlock_types.h>26#include <linux/stddef.h>27#include <linux/string.h>28#include <linux/types.h>29#include <linux/uaccess.h>30#include <linux/user_namespace.h>31#include <linux/xarray.h>32#include <uapi/linux/android/binder.h>33#include <uapi/linux/android/binderfs.h>34 35#include "binder_internal.h"36 37#define FIRST_INODE 138#define SECOND_INODE 239#define INODE_OFFSET 340#define BINDERFS_MAX_MINOR (1U << MINORBITS)41/* Ensure that the initial ipc namespace always has devices available. */42#define BINDERFS_MAX_MINOR_CAPPED (BINDERFS_MAX_MINOR - 4)43 44static dev_t binderfs_dev;45static DEFINE_MUTEX(binderfs_minors_mutex);46static DEFINE_IDA(binderfs_minors);47 48enum binderfs_param {49 Opt_max,50 Opt_stats_mode,51};52 53enum binderfs_stats_mode {54 binderfs_stats_mode_unset,55 binderfs_stats_mode_global,56};57 58struct binder_features {59 bool oneway_spam_detection;60 bool extended_error;61 bool freeze_notification;62};63 64static const struct constant_table binderfs_param_stats[] = {65 { "global", binderfs_stats_mode_global },66 {}67};68 69static const struct fs_parameter_spec binderfs_fs_parameters[] = {70 fsparam_u32("max", Opt_max),71 fsparam_enum("stats", Opt_stats_mode, binderfs_param_stats),72 {}73};74 75static struct binder_features binder_features = {76 .oneway_spam_detection = true,77 .extended_error = true,78 .freeze_notification = true,79};80 81static inline struct binderfs_info *BINDERFS_SB(const struct super_block *sb)82{83 return sb->s_fs_info;84}85 86bool is_binderfs_device(const struct inode *inode)87{88 if (inode->i_sb->s_magic == BINDERFS_SUPER_MAGIC)89 return true;90 91 return false;92}93 94/**95 * binderfs_binder_device_create - allocate inode from super block of a96 * binderfs mount97 * @ref_inode: inode from which the super block will be taken98 * @userp: buffer to copy information about new device for userspace to99 * @req: struct binderfs_device as copied from userspace100 *101 * This function allocates a new binder_device and reserves a new minor102 * number for it.103 * Minor numbers are limited and tracked globally in binderfs_minors. The104 * function will stash a struct binder_device for the specific binder105 * device in i_private of the inode.106 * It will go on to allocate a new inode from the super block of the107 * filesystem mount, stash a struct binder_device in its i_private field108 * and attach a dentry to that inode.109 *110 * Return: 0 on success, negative errno on failure111 */112static int binderfs_binder_device_create(struct inode *ref_inode,113 struct binderfs_device __user *userp,114 struct binderfs_device *req)115{116 int minor, ret;117 struct dentry *dentry, *root;118 struct binder_device *device;119 char *name = NULL;120 size_t name_len;121 struct inode *inode = NULL;122 struct super_block *sb = ref_inode->i_sb;123 struct binderfs_info *info = sb->s_fs_info;124#if defined(CONFIG_IPC_NS)125 bool use_reserve = (info->ipc_ns == &init_ipc_ns);126#else127 bool use_reserve = true;128#endif129 130 /* Reserve new minor number for the new device. */131 mutex_lock(&binderfs_minors_mutex);132 if (++info->device_count <= info->mount_opts.max)133 minor = ida_alloc_max(&binderfs_minors,134 use_reserve ? BINDERFS_MAX_MINOR :135 BINDERFS_MAX_MINOR_CAPPED,136 GFP_KERNEL);137 else138 minor = -ENOSPC;139 if (minor < 0) {140 --info->device_count;141 mutex_unlock(&binderfs_minors_mutex);142 return minor;143 }144 mutex_unlock(&binderfs_minors_mutex);145 146 ret = -ENOMEM;147 device = kzalloc(sizeof(*device), GFP_KERNEL);148 if (!device)149 goto err;150 151 inode = new_inode(sb);152 if (!inode)153 goto err;154 155 inode->i_ino = minor + INODE_OFFSET;156 simple_inode_init_ts(inode);157 init_special_inode(inode, S_IFCHR | 0600,158 MKDEV(MAJOR(binderfs_dev), minor));159 inode->i_fop = &binder_fops;160 inode->i_uid = info->root_uid;161 inode->i_gid = info->root_gid;162 163 req->name[BINDERFS_MAX_NAME] = '\0'; /* NUL-terminate */164 name_len = strlen(req->name);165 /* Make sure to include terminating NUL byte */166 name = kmemdup(req->name, name_len + 1, GFP_KERNEL);167 if (!name)168 goto err;169 170 refcount_set(&device->ref, 1);171 device->binderfs_inode = inode;172 device->context.binder_context_mgr_uid = INVALID_UID;173 device->context.name = name;174 device->miscdev.name = name;175 device->miscdev.minor = minor;176 mutex_init(&device->context.context_mgr_node_lock);177 178 req->major = MAJOR(binderfs_dev);179 req->minor = minor;180 181 if (userp && copy_to_user(userp, req, sizeof(*req))) {182 ret = -EFAULT;183 goto err;184 }185 186 root = sb->s_root;187 inode_lock(d_inode(root));188 189 /* look it up */190 dentry = lookup_one_len(name, root, name_len);191 if (IS_ERR(dentry)) {192 inode_unlock(d_inode(root));193 ret = PTR_ERR(dentry);194 goto err;195 }196 197 if (d_really_is_positive(dentry)) {198 /* already exists */199 dput(dentry);200 inode_unlock(d_inode(root));201 ret = -EEXIST;202 goto err;203 }204 205 inode->i_private = device;206 d_instantiate(dentry, inode);207 fsnotify_create(root->d_inode, dentry);208 inode_unlock(d_inode(root));209 210 return 0;211 212err:213 kfree(name);214 kfree(device);215 mutex_lock(&binderfs_minors_mutex);216 --info->device_count;217 ida_free(&binderfs_minors, minor);218 mutex_unlock(&binderfs_minors_mutex);219 iput(inode);220 221 return ret;222}223 224/**225 * binder_ctl_ioctl - handle binder device node allocation requests226 *227 * The request handler for the binder-control device. All requests operate on228 * the binderfs mount the binder-control device resides in:229 * - BINDER_CTL_ADD230 * Allocate a new binder device.231 *232 * Return: %0 on success, negative errno on failure.233 */234static long binder_ctl_ioctl(struct file *file, unsigned int cmd,235 unsigned long arg)236{237 int ret = -EINVAL;238 struct inode *inode = file_inode(file);239 struct binderfs_device __user *device = (struct binderfs_device __user *)arg;240 struct binderfs_device device_req;241 242 switch (cmd) {243 case BINDER_CTL_ADD:244 ret = copy_from_user(&device_req, device, sizeof(device_req));245 if (ret) {246 ret = -EFAULT;247 break;248 }249 250 ret = binderfs_binder_device_create(inode, device, &device_req);251 break;252 default:253 break;254 }255 256 return ret;257}258 259static void binderfs_evict_inode(struct inode *inode)260{261 struct binder_device *device = inode->i_private;262 struct binderfs_info *info = BINDERFS_SB(inode->i_sb);263 264 clear_inode(inode);265 266 if (!S_ISCHR(inode->i_mode) || !device)267 return;268 269 mutex_lock(&binderfs_minors_mutex);270 --info->device_count;271 ida_free(&binderfs_minors, device->miscdev.minor);272 mutex_unlock(&binderfs_minors_mutex);273 274 if (refcount_dec_and_test(&device->ref)) {275 kfree(device->context.name);276 kfree(device);277 }278}279 280static int binderfs_fs_context_parse_param(struct fs_context *fc,281 struct fs_parameter *param)282{283 int opt;284 struct binderfs_mount_opts *ctx = fc->fs_private;285 struct fs_parse_result result;286 287 opt = fs_parse(fc, binderfs_fs_parameters, param, &result);288 if (opt < 0)289 return opt;290 291 switch (opt) {292 case Opt_max:293 if (result.uint_32 > BINDERFS_MAX_MINOR)294 return invalfc(fc, "Bad value for '%s'", param->key);295 296 ctx->max = result.uint_32;297 break;298 case Opt_stats_mode:299 if (!capable(CAP_SYS_ADMIN))300 return -EPERM;301 302 ctx->stats_mode = result.uint_32;303 break;304 default:305 return invalfc(fc, "Unsupported parameter '%s'", param->key);306 }307 308 return 0;309}310 311static int binderfs_fs_context_reconfigure(struct fs_context *fc)312{313 struct binderfs_mount_opts *ctx = fc->fs_private;314 struct binderfs_info *info = BINDERFS_SB(fc->root->d_sb);315 316 if (info->mount_opts.stats_mode != ctx->stats_mode)317 return invalfc(fc, "Binderfs stats mode cannot be changed during a remount");318 319 info->mount_opts.stats_mode = ctx->stats_mode;320 info->mount_opts.max = ctx->max;321 return 0;322}323 324static int binderfs_show_options(struct seq_file *seq, struct dentry *root)325{326 struct binderfs_info *info = BINDERFS_SB(root->d_sb);327 328 if (info->mount_opts.max <= BINDERFS_MAX_MINOR)329 seq_printf(seq, ",max=%d", info->mount_opts.max);330 331 switch (info->mount_opts.stats_mode) {332 case binderfs_stats_mode_unset:333 break;334 case binderfs_stats_mode_global:335 seq_printf(seq, ",stats=global");336 break;337 }338 339 return 0;340}341 342static const struct super_operations binderfs_super_ops = {343 .evict_inode = binderfs_evict_inode,344 .show_options = binderfs_show_options,345 .statfs = simple_statfs,346};347 348static inline bool is_binderfs_control_device(const struct dentry *dentry)349{350 struct binderfs_info *info = dentry->d_sb->s_fs_info;351 352 return info->control_dentry == dentry;353}354 355static int binderfs_rename(struct mnt_idmap *idmap,356 struct inode *old_dir, struct dentry *old_dentry,357 struct inode *new_dir, struct dentry *new_dentry,358 unsigned int flags)359{360 if (is_binderfs_control_device(old_dentry) ||361 is_binderfs_control_device(new_dentry))362 return -EPERM;363 364 return simple_rename(idmap, old_dir, old_dentry, new_dir,365 new_dentry, flags);366}367 368static int binderfs_unlink(struct inode *dir, struct dentry *dentry)369{370 if (is_binderfs_control_device(dentry))371 return -EPERM;372 373 return simple_unlink(dir, dentry);374}375 376static const struct file_operations binder_ctl_fops = {377 .owner = THIS_MODULE,378 .open = nonseekable_open,379 .unlocked_ioctl = binder_ctl_ioctl,380 .compat_ioctl = binder_ctl_ioctl,381 .llseek = noop_llseek,382};383 384/**385 * binderfs_binder_ctl_create - create a new binder-control device386 * @sb: super block of the binderfs mount387 *388 * This function creates a new binder-control device node in the binderfs mount389 * referred to by @sb.390 *391 * Return: 0 on success, negative errno on failure392 */393static int binderfs_binder_ctl_create(struct super_block *sb)394{395 int minor, ret;396 struct dentry *dentry;397 struct binder_device *device;398 struct inode *inode = NULL;399 struct dentry *root = sb->s_root;400 struct binderfs_info *info = sb->s_fs_info;401#if defined(CONFIG_IPC_NS)402 bool use_reserve = (info->ipc_ns == &init_ipc_ns);403#else404 bool use_reserve = true;405#endif406 407 device = kzalloc(sizeof(*device), GFP_KERNEL);408 if (!device)409 return -ENOMEM;410 411 /* If we have already created a binder-control node, return. */412 if (info->control_dentry) {413 ret = 0;414 goto out;415 }416 417 ret = -ENOMEM;418 inode = new_inode(sb);419 if (!inode)420 goto out;421 422 /* Reserve a new minor number for the new device. */423 mutex_lock(&binderfs_minors_mutex);424 minor = ida_alloc_max(&binderfs_minors,425 use_reserve ? BINDERFS_MAX_MINOR :426 BINDERFS_MAX_MINOR_CAPPED,427 GFP_KERNEL);428 mutex_unlock(&binderfs_minors_mutex);429 if (minor < 0) {430 ret = minor;431 goto out;432 }433 434 inode->i_ino = SECOND_INODE;435 simple_inode_init_ts(inode);436 init_special_inode(inode, S_IFCHR | 0600,437 MKDEV(MAJOR(binderfs_dev), minor));438 inode->i_fop = &binder_ctl_fops;439 inode->i_uid = info->root_uid;440 inode->i_gid = info->root_gid;441 442 refcount_set(&device->ref, 1);443 device->binderfs_inode = inode;444 device->miscdev.minor = minor;445 446 dentry = d_alloc_name(root, "binder-control");447 if (!dentry)448 goto out;449 450 inode->i_private = device;451 info->control_dentry = dentry;452 d_add(dentry, inode);453 454 return 0;455 456out:457 kfree(device);458 iput(inode);459 460 return ret;461}462 463static const struct inode_operations binderfs_dir_inode_operations = {464 .lookup = simple_lookup,465 .rename = binderfs_rename,466 .unlink = binderfs_unlink,467};468 469static struct inode *binderfs_make_inode(struct super_block *sb, int mode)470{471 struct inode *ret;472 473 ret = new_inode(sb);474 if (ret) {475 ret->i_ino = iunique(sb, BINDERFS_MAX_MINOR + INODE_OFFSET);476 ret->i_mode = mode;477 simple_inode_init_ts(ret);478 }479 return ret;480}481 482static struct dentry *binderfs_create_dentry(struct dentry *parent,483 const char *name)484{485 struct dentry *dentry;486 487 dentry = lookup_one_len(name, parent, strlen(name));488 if (IS_ERR(dentry))489 return dentry;490 491 /* Return error if the file/dir already exists. */492 if (d_really_is_positive(dentry)) {493 dput(dentry);494 return ERR_PTR(-EEXIST);495 }496 497 return dentry;498}499 500void binderfs_remove_file(struct dentry *dentry)501{502 struct inode *parent_inode;503 504 parent_inode = d_inode(dentry->d_parent);505 inode_lock(parent_inode);506 if (simple_positive(dentry)) {507 dget(dentry);508 simple_unlink(parent_inode, dentry);509 d_delete(dentry);510 dput(dentry);511 }512 inode_unlock(parent_inode);513}514 515struct dentry *binderfs_create_file(struct dentry *parent, const char *name,516 const struct file_operations *fops,517 void *data)518{519 struct dentry *dentry;520 struct inode *new_inode, *parent_inode;521 struct super_block *sb;522 523 parent_inode = d_inode(parent);524 inode_lock(parent_inode);525 526 dentry = binderfs_create_dentry(parent, name);527 if (IS_ERR(dentry))528 goto out;529 530 sb = parent_inode->i_sb;531 new_inode = binderfs_make_inode(sb, S_IFREG | 0444);532 if (!new_inode) {533 dput(dentry);534 dentry = ERR_PTR(-ENOMEM);535 goto out;536 }537 538 new_inode->i_fop = fops;539 new_inode->i_private = data;540 d_instantiate(dentry, new_inode);541 fsnotify_create(parent_inode, dentry);542 543out:544 inode_unlock(parent_inode);545 return dentry;546}547 548static struct dentry *binderfs_create_dir(struct dentry *parent,549 const char *name)550{551 struct dentry *dentry;552 struct inode *new_inode, *parent_inode;553 struct super_block *sb;554 555 parent_inode = d_inode(parent);556 inode_lock(parent_inode);557 558 dentry = binderfs_create_dentry(parent, name);559 if (IS_ERR(dentry))560 goto out;561 562 sb = parent_inode->i_sb;563 new_inode = binderfs_make_inode(sb, S_IFDIR | 0755);564 if (!new_inode) {565 dput(dentry);566 dentry = ERR_PTR(-ENOMEM);567 goto out;568 }569 570 new_inode->i_fop = &simple_dir_operations;571 new_inode->i_op = &simple_dir_inode_operations;572 573 set_nlink(new_inode, 2);574 d_instantiate(dentry, new_inode);575 inc_nlink(parent_inode);576 fsnotify_mkdir(parent_inode, dentry);577 578out:579 inode_unlock(parent_inode);580 return dentry;581}582 583static int binder_features_show(struct seq_file *m, void *unused)584{585 bool *feature = m->private;586 587 seq_printf(m, "%d\n", *feature);588 589 return 0;590}591DEFINE_SHOW_ATTRIBUTE(binder_features);592 593static int init_binder_features(struct super_block *sb)594{595 struct dentry *dentry, *dir;596 597 dir = binderfs_create_dir(sb->s_root, "features");598 if (IS_ERR(dir))599 return PTR_ERR(dir);600 601 dentry = binderfs_create_file(dir, "oneway_spam_detection",602 &binder_features_fops,603 &binder_features.oneway_spam_detection);604 if (IS_ERR(dentry))605 return PTR_ERR(dentry);606 607 dentry = binderfs_create_file(dir, "extended_error",608 &binder_features_fops,609 &binder_features.extended_error);610 if (IS_ERR(dentry))611 return PTR_ERR(dentry);612 613 dentry = binderfs_create_file(dir, "freeze_notification",614 &binder_features_fops,615 &binder_features.freeze_notification);616 if (IS_ERR(dentry))617 return PTR_ERR(dentry);618 619 return 0;620}621 622static int init_binder_logs(struct super_block *sb)623{624 struct dentry *binder_logs_root_dir, *dentry, *proc_log_dir;625 const struct binder_debugfs_entry *db_entry;626 struct binderfs_info *info;627 int ret = 0;628 629 binder_logs_root_dir = binderfs_create_dir(sb->s_root,630 "binder_logs");631 if (IS_ERR(binder_logs_root_dir)) {632 ret = PTR_ERR(binder_logs_root_dir);633 goto out;634 }635 636 binder_for_each_debugfs_entry(db_entry) {637 dentry = binderfs_create_file(binder_logs_root_dir,638 db_entry->name,639 db_entry->fops,640 db_entry->data);641 if (IS_ERR(dentry)) {642 ret = PTR_ERR(dentry);643 goto out;644 }645 }646 647 proc_log_dir = binderfs_create_dir(binder_logs_root_dir, "proc");648 if (IS_ERR(proc_log_dir)) {649 ret = PTR_ERR(proc_log_dir);650 goto out;651 }652 info = sb->s_fs_info;653 info->proc_log_dir = proc_log_dir;654 655out:656 return ret;657}658 659static int binderfs_fill_super(struct super_block *sb, struct fs_context *fc)660{661 int ret;662 struct binderfs_info *info;663 struct binderfs_mount_opts *ctx = fc->fs_private;664 struct inode *inode = NULL;665 struct binderfs_device device_info = {};666 const char *name;667 size_t len;668 669 sb->s_blocksize = PAGE_SIZE;670 sb->s_blocksize_bits = PAGE_SHIFT;671 672 /*673 * The binderfs filesystem can be mounted by userns root in a674 * non-initial userns. By default such mounts have the SB_I_NODEV flag675 * set in s_iflags to prevent security issues where userns root can676 * just create random device nodes via mknod() since it owns the677 * filesystem mount. But binderfs does not allow to create any files678 * including devices nodes. The only way to create binder devices nodes679 * is through the binder-control device which userns root is explicitly680 * allowed to do. So removing the SB_I_NODEV flag from s_iflags is both681 * necessary and safe.682 */683 sb->s_iflags &= ~SB_I_NODEV;684 sb->s_iflags |= SB_I_NOEXEC;685 sb->s_magic = BINDERFS_SUPER_MAGIC;686 sb->s_op = &binderfs_super_ops;687 sb->s_time_gran = 1;688 689 sb->s_fs_info = kzalloc(sizeof(struct binderfs_info), GFP_KERNEL);690 if (!sb->s_fs_info)691 return -ENOMEM;692 info = sb->s_fs_info;693 694 info->ipc_ns = get_ipc_ns(current->nsproxy->ipc_ns);695 696 info->root_gid = make_kgid(sb->s_user_ns, 0);697 if (!gid_valid(info->root_gid))698 info->root_gid = GLOBAL_ROOT_GID;699 info->root_uid = make_kuid(sb->s_user_ns, 0);700 if (!uid_valid(info->root_uid))701 info->root_uid = GLOBAL_ROOT_UID;702 info->mount_opts.max = ctx->max;703 info->mount_opts.stats_mode = ctx->stats_mode;704 705 inode = new_inode(sb);706 if (!inode)707 return -ENOMEM;708 709 inode->i_ino = FIRST_INODE;710 inode->i_fop = &simple_dir_operations;711 inode->i_mode = S_IFDIR | 0755;712 simple_inode_init_ts(inode);713 inode->i_op = &binderfs_dir_inode_operations;714 set_nlink(inode, 2);715 716 sb->s_root = d_make_root(inode);717 if (!sb->s_root)718 return -ENOMEM;719 720 ret = binderfs_binder_ctl_create(sb);721 if (ret)722 return ret;723 724 name = binder_devices_param;725 for (len = strcspn(name, ","); len > 0; len = strcspn(name, ",")) {726 strscpy(device_info.name, name, len + 1);727 ret = binderfs_binder_device_create(inode, NULL, &device_info);728 if (ret)729 return ret;730 name += len;731 if (*name == ',')732 name++;733 }734 735 ret = init_binder_features(sb);736 if (ret)737 return ret;738 739 if (info->mount_opts.stats_mode == binderfs_stats_mode_global)740 return init_binder_logs(sb);741 742 return 0;743}744 745static int binderfs_fs_context_get_tree(struct fs_context *fc)746{747 return get_tree_nodev(fc, binderfs_fill_super);748}749 750static void binderfs_fs_context_free(struct fs_context *fc)751{752 struct binderfs_mount_opts *ctx = fc->fs_private;753 754 kfree(ctx);755}756 757static const struct fs_context_operations binderfs_fs_context_ops = {758 .free = binderfs_fs_context_free,759 .get_tree = binderfs_fs_context_get_tree,760 .parse_param = binderfs_fs_context_parse_param,761 .reconfigure = binderfs_fs_context_reconfigure,762};763 764static int binderfs_init_fs_context(struct fs_context *fc)765{766 struct binderfs_mount_opts *ctx;767 768 ctx = kzalloc(sizeof(struct binderfs_mount_opts), GFP_KERNEL);769 if (!ctx)770 return -ENOMEM;771 772 ctx->max = BINDERFS_MAX_MINOR;773 ctx->stats_mode = binderfs_stats_mode_unset;774 775 fc->fs_private = ctx;776 fc->ops = &binderfs_fs_context_ops;777 778 return 0;779}780 781static void binderfs_kill_super(struct super_block *sb)782{783 struct binderfs_info *info = sb->s_fs_info;784 785 /*786 * During inode eviction struct binderfs_info is needed.787 * So first wipe the super_block then free struct binderfs_info.788 */789 kill_litter_super(sb);790 791 if (info && info->ipc_ns)792 put_ipc_ns(info->ipc_ns);793 794 kfree(info);795}796 797static struct file_system_type binder_fs_type = {798 .name = "binder",799 .init_fs_context = binderfs_init_fs_context,800 .parameters = binderfs_fs_parameters,801 .kill_sb = binderfs_kill_super,802 .fs_flags = FS_USERNS_MOUNT,803};804 805int __init init_binderfs(void)806{807 int ret;808 const char *name;809 size_t len;810 811 /* Verify that the default binderfs device names are valid. */812 name = binder_devices_param;813 for (len = strcspn(name, ","); len > 0; len = strcspn(name, ",")) {814 if (len > BINDERFS_MAX_NAME)815 return -E2BIG;816 name += len;817 if (*name == ',')818 name++;819 }820 821 /* Allocate new major number for binderfs. */822 ret = alloc_chrdev_region(&binderfs_dev, 0, BINDERFS_MAX_MINOR,823 "binder");824 if (ret)825 return ret;826 827 ret = register_filesystem(&binder_fs_type);828 if (ret) {829 unregister_chrdev_region(binderfs_dev, BINDERFS_MAX_MINOR);830 return ret;831 }832 833 return ret;834}835