// SPDX-License-Identifier: GPL-2.0-only /* * inode.c - part of tracefs, a pseudo file system for activating tracing * * Based on debugfs by: Greg Kroah-Hartman * * Copyright (C) 2014 Red Hat Inc, author: Steven Rostedt * * tracefs is the file system that is used by the tracing infrastructure. */ #include #include #include #include #include #include #include #include #include #include #include #include #include "internal.h" #define TRACEFS_DEFAULT_MODE 0700 static struct kmem_cache *tracefs_inode_cachep __ro_after_init; static struct vfsmount *tracefs_mount; static int tracefs_mount_count; static bool tracefs_registered; /* * Keep track of all tracefs_inodes in order to update their * flags if necessary on a remount. */ static DEFINE_SPINLOCK(tracefs_inode_lock); static LIST_HEAD(tracefs_inodes); static struct inode *tracefs_alloc_inode(struct super_block *sb) { struct tracefs_inode *ti; unsigned long flags; ti = kmem_cache_alloc(tracefs_inode_cachep, GFP_KERNEL); if (!ti) return NULL; spin_lock_irqsave(&tracefs_inode_lock, flags); list_add_rcu(&ti->list, &tracefs_inodes); spin_unlock_irqrestore(&tracefs_inode_lock, flags); return &ti->vfs_inode; } static void tracefs_free_inode_rcu(struct rcu_head *rcu) { struct tracefs_inode *ti; ti = container_of(rcu, struct tracefs_inode, rcu); kmem_cache_free(tracefs_inode_cachep, ti); } static void tracefs_free_inode(struct inode *inode) { struct tracefs_inode *ti = get_tracefs(inode); unsigned long flags; spin_lock_irqsave(&tracefs_inode_lock, flags); list_del_rcu(&ti->list); spin_unlock_irqrestore(&tracefs_inode_lock, flags); call_rcu(&ti->rcu, tracefs_free_inode_rcu); } static ssize_t default_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos) { return 0; } static ssize_t default_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { return count; } static const struct file_operations tracefs_file_operations = { .read = default_read_file, .write = default_write_file, .open = simple_open, .llseek = noop_llseek, }; static struct tracefs_dir_ops { int (*mkdir)(const char *name); int (*rmdir)(const char *name); } tracefs_ops __ro_after_init; static char *get_dname(struct dentry *dentry) { const char *dname; char *name; int len = dentry->d_name.len; dname = dentry->d_name.name; name = kmalloc(len + 1, GFP_KERNEL); if (!name) return NULL; memcpy(name, dname, len); name[len] = 0; return name; } static int tracefs_syscall_mkdir(struct mnt_idmap *idmap, struct inode *inode, struct dentry *dentry, umode_t mode) { struct tracefs_inode *ti; char *name; int ret; name = get_dname(dentry); if (!name) return -ENOMEM; /* * This is a new directory that does not take the default of * the rootfs. It becomes the default permissions for all the * files and directories underneath it. */ ti = get_tracefs(inode); ti->flags |= TRACEFS_INSTANCE_INODE; ti->private = inode; /* * The mkdir call can call the generic functions that create * the files within the tracefs system. It is up to the individual * mkdir routine to handle races. */ inode_unlock(inode); ret = tracefs_ops.mkdir(name); inode_lock(inode); kfree(name); return ret; } static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry) { char *name; int ret; name = get_dname(dentry); if (!name) return -ENOMEM; /* * The rmdir call can call the generic functions that create * the files within the tracefs system. It is up to the individual * rmdir routine to handle races. * This time we need to unlock not only the parent (inode) but * also the directory that is being deleted. */ inode_unlock(inode); inode_unlock(d_inode(dentry)); ret = tracefs_ops.rmdir(name); inode_lock_nested(inode, I_MUTEX_PARENT); inode_lock(d_inode(dentry)); kfree(name); return ret; } static void set_tracefs_inode_owner(struct inode *inode) { struct tracefs_inode *ti = get_tracefs(inode); struct inode *root_inode = ti->private; kuid_t uid; kgid_t gid; uid = root_inode->i_uid; gid = root_inode->i_gid; /* * If the root is not the mount point, then check the root's * permissions. If it was never set, then default to the * mount point. */ if (root_inode != d_inode(root_inode->i_sb->s_root)) { struct tracefs_inode *rti; rti = get_tracefs(root_inode); root_inode = d_inode(root_inode->i_sb->s_root); if (!(rti->flags & TRACEFS_UID_PERM_SET)) uid = root_inode->i_uid; if (!(rti->flags & TRACEFS_GID_PERM_SET)) gid = root_inode->i_gid; } /* * If this inode has never been referenced, then update * the permissions to the superblock. */ if (!(ti->flags & TRACEFS_UID_PERM_SET)) inode->i_uid = uid; if (!(ti->flags & TRACEFS_GID_PERM_SET)) inode->i_gid = gid; } static int tracefs_permission(struct mnt_idmap *idmap, struct inode *inode, int mask) { set_tracefs_inode_owner(inode); return generic_permission(idmap, inode, mask); } static int tracefs_getattr(struct mnt_idmap *idmap, const struct path *path, struct kstat *stat, u32 request_mask, unsigned int flags) { struct inode *inode = d_backing_inode(path->dentry); set_tracefs_inode_owner(inode); generic_fillattr(idmap, request_mask, inode, stat); return 0; } static int tracefs_setattr(struct mnt_idmap *idmap, struct dentry *dentry, struct iattr *attr) { unsigned int ia_valid = attr->ia_valid; struct inode *inode = d_inode(dentry); struct tracefs_inode *ti = get_tracefs(inode); if (ia_valid & ATTR_UID) ti->flags |= TRACEFS_UID_PERM_SET; if (ia_valid & ATTR_GID) ti->flags |= TRACEFS_GID_PERM_SET; return simple_setattr(idmap, dentry, attr); } static const struct inode_operations tracefs_instance_dir_inode_operations = { .lookup = simple_lookup, .mkdir = tracefs_syscall_mkdir, .rmdir = tracefs_syscall_rmdir, .permission = tracefs_permission, .getattr = tracefs_getattr, .setattr = tracefs_setattr, }; static const struct inode_operations tracefs_dir_inode_operations = { .lookup = simple_lookup, .permission = tracefs_permission, .getattr = tracefs_getattr, .setattr = tracefs_setattr, }; static const struct inode_operations tracefs_file_inode_operations = { .permission = tracefs_permission, .getattr = tracefs_getattr, .setattr = tracefs_setattr, }; struct inode *tracefs_get_inode(struct super_block *sb) { struct inode *inode = new_inode(sb); if (inode) { inode->i_ino = get_next_ino(); simple_inode_init_ts(inode); } return inode; } struct tracefs_fs_info { kuid_t uid; kgid_t gid; umode_t mode; /* Opt_* bitfield. */ unsigned int opts; }; enum { Opt_uid, Opt_gid, Opt_mode, }; static const struct fs_parameter_spec tracefs_param_specs[] = { fsparam_gid ("gid", Opt_gid), fsparam_u32oct ("mode", Opt_mode), fsparam_uid ("uid", Opt_uid), {} }; static int tracefs_parse_param(struct fs_context *fc, struct fs_parameter *param) { struct tracefs_fs_info *opts = fc->s_fs_info; struct fs_parse_result result; int opt; opt = fs_parse(fc, tracefs_param_specs, param, &result); if (opt < 0) return opt; switch (opt) { case Opt_uid: opts->uid = result.uid; break; case Opt_gid: opts->gid = result.gid; break; case Opt_mode: opts->mode = result.uint_32 & S_IALLUGO; break; /* * We might like to report bad mount options here; * but traditionally tracefs has ignored all mount options */ } opts->opts |= BIT(opt); return 0; } static int tracefs_apply_options(struct super_block *sb, bool remount) { struct tracefs_fs_info *fsi = sb->s_fs_info; struct inode *inode = d_inode(sb->s_root); struct tracefs_inode *ti; bool update_uid, update_gid; umode_t tmp_mode; /* * On remount, only reset mode/uid/gid if they were provided as mount * options. */ if (!remount || fsi->opts & BIT(Opt_mode)) { tmp_mode = READ_ONCE(inode->i_mode) & ~S_IALLUGO; tmp_mode |= fsi->mode; WRITE_ONCE(inode->i_mode, tmp_mode); } if (!remount || fsi->opts & BIT(Opt_uid)) inode->i_uid = fsi->uid; if (!remount || fsi->opts & BIT(Opt_gid)) inode->i_gid = fsi->gid; if (remount && (fsi->opts & BIT(Opt_uid) || fsi->opts & BIT(Opt_gid))) { update_uid = fsi->opts & BIT(Opt_uid); update_gid = fsi->opts & BIT(Opt_gid); rcu_read_lock(); list_for_each_entry_rcu(ti, &tracefs_inodes, list) { if (update_uid) { ti->flags &= ~TRACEFS_UID_PERM_SET; ti->vfs_inode.i_uid = fsi->uid; } if (update_gid) { ti->flags &= ~TRACEFS_GID_PERM_SET; ti->vfs_inode.i_gid = fsi->gid; } /* * Note, the above ti->vfs_inode updates are * used in eventfs_remount() so they must come * before calling it. */ if (ti->flags & TRACEFS_EVENT_INODE) eventfs_remount(ti, update_uid, update_gid); } rcu_read_unlock(); } return 0; } static int tracefs_reconfigure(struct fs_context *fc) { struct super_block *sb = fc->root->d_sb; struct tracefs_fs_info *sb_opts = sb->s_fs_info; struct tracefs_fs_info *new_opts = fc->s_fs_info; sync_filesystem(sb); /* structure copy of new mount options to sb */ *sb_opts = *new_opts; return tracefs_apply_options(sb, true); } static int tracefs_show_options(struct seq_file *m, struct dentry *root) { struct tracefs_fs_info *fsi = root->d_sb->s_fs_info; if (!uid_eq(fsi->uid, GLOBAL_ROOT_UID)) seq_printf(m, ",uid=%u", from_kuid_munged(&init_user_ns, fsi->uid)); if (!gid_eq(fsi->gid, GLOBAL_ROOT_GID)) seq_printf(m, ",gid=%u", from_kgid_munged(&init_user_ns, fsi->gid)); if (fsi->mode != TRACEFS_DEFAULT_MODE) seq_printf(m, ",mode=%o", fsi->mode); return 0; } static int tracefs_drop_inode(struct inode *inode) { struct tracefs_inode *ti = get_tracefs(inode); /* * This inode is being freed and cannot be used for * eventfs. Clear the flag so that it doesn't call into * eventfs during the remount flag updates. The eventfs_inode * gets freed after an RCU cycle, so the content will still * be safe if the iteration is going on now. */ ti->flags &= ~TRACEFS_EVENT_INODE; return 1; } static const struct super_operations tracefs_super_operations = { .alloc_inode = tracefs_alloc_inode, .free_inode = tracefs_free_inode, .drop_inode = tracefs_drop_inode, .statfs = simple_statfs, .show_options = tracefs_show_options, }; /* * It would be cleaner if eventfs had its own dentry ops. * * Note that d_revalidate is called potentially under RCU, * so it can't take the eventfs mutex etc. It's fine - if * we open a file just as it's marked dead, things will * still work just fine, and just see the old stale case. */ static void tracefs_d_release(struct dentry *dentry) { if (dentry->d_fsdata) eventfs_d_release(dentry); } static int tracefs_d_revalidate(struct dentry *dentry, unsigned int flags) { struct eventfs_inode *ei = dentry->d_fsdata; return !(ei && ei->is_freed); } static const struct dentry_operations tracefs_dentry_operations = { .d_revalidate = tracefs_d_revalidate, .d_release = tracefs_d_release, }; static int tracefs_fill_super(struct super_block *sb, struct fs_context *fc) { static const struct tree_descr trace_files[] = {{""}}; int err; err = simple_fill_super(sb, TRACEFS_MAGIC, trace_files); if (err) return err; sb->s_op = &tracefs_super_operations; sb->s_d_op = &tracefs_dentry_operations; tracefs_apply_options(sb, false); return 0; } static int tracefs_get_tree(struct fs_context *fc) { return get_tree_single(fc, tracefs_fill_super); } static void tracefs_free_fc(struct fs_context *fc) { kfree(fc->s_fs_info); } static const struct fs_context_operations tracefs_context_ops = { .free = tracefs_free_fc, .parse_param = tracefs_parse_param, .get_tree = tracefs_get_tree, .reconfigure = tracefs_reconfigure, }; static int tracefs_init_fs_context(struct fs_context *fc) { struct tracefs_fs_info *fsi; fsi = kzalloc(sizeof(struct tracefs_fs_info), GFP_KERNEL); if (!fsi) return -ENOMEM; fsi->mode = TRACEFS_DEFAULT_MODE; fc->s_fs_info = fsi; fc->ops = &tracefs_context_ops; return 0; } static struct file_system_type trace_fs_type = { .owner = THIS_MODULE, .name = "tracefs", .init_fs_context = tracefs_init_fs_context, .parameters = tracefs_param_specs, .kill_sb = kill_litter_super, }; MODULE_ALIAS_FS("tracefs"); struct dentry *tracefs_start_creating(const char *name, struct dentry *parent) { struct dentry *dentry; int error; pr_debug("tracefs: creating file '%s'\n",name); error = simple_pin_fs(&trace_fs_type, &tracefs_mount, &tracefs_mount_count); if (error) return ERR_PTR(error); /* If the parent is not specified, we create it in the root. * We need the root dentry to do this, which is in the super * block. A pointer to that is in the struct vfsmount that we * have around. */ if (!parent) parent = tracefs_mount->mnt_root; inode_lock(d_inode(parent)); if (unlikely(IS_DEADDIR(d_inode(parent)))) dentry = ERR_PTR(-ENOENT); else dentry = lookup_one_len(name, parent, strlen(name)); if (!IS_ERR(dentry) && d_inode(dentry)) { dput(dentry); dentry = ERR_PTR(-EEXIST); } if (IS_ERR(dentry)) { inode_unlock(d_inode(parent)); simple_release_fs(&tracefs_mount, &tracefs_mount_count); } return dentry; } struct dentry *tracefs_failed_creating(struct dentry *dentry) { inode_unlock(d_inode(dentry->d_parent)); dput(dentry); simple_release_fs(&tracefs_mount, &tracefs_mount_count); return NULL; } struct dentry *tracefs_end_creating(struct dentry *dentry) { inode_unlock(d_inode(dentry->d_parent)); return dentry; } /* Find the inode that this will use for default */ static struct inode *instance_inode(struct dentry *parent, struct inode *inode) { struct tracefs_inode *ti; /* If parent is NULL then use root inode */ if (!parent) return d_inode(inode->i_sb->s_root); /* Find the inode that is flagged as an instance or the root inode */ while (!IS_ROOT(parent)) { ti = get_tracefs(d_inode(parent)); if (ti->flags & TRACEFS_INSTANCE_INODE) break; parent = parent->d_parent; } return d_inode(parent); } /** * tracefs_create_file - create a file in the tracefs filesystem * @name: a pointer to a string containing the name of the file to create. * @mode: the permission that the file should have. * @parent: a pointer to the parent dentry for this file. This should be a * directory dentry if set. If this parameter is NULL, then the * file will be created in the root of the tracefs filesystem. * @data: a pointer to something that the caller will want to get to later * on. The inode.i_private pointer will point to this value on * the open() call. * @fops: a pointer to a struct file_operations that should be used for * this file. * * This is the basic "create a file" function for tracefs. It allows for a * wide range of flexibility in creating a file, or a directory (if you want * to create a directory, the tracefs_create_dir() function is * recommended to be used instead.) * * This function will return a pointer to a dentry if it succeeds. This * pointer must be passed to the tracefs_remove() function when the file is * to be removed (no automatic cleanup happens if your module is unloaded, * you are responsible here.) If an error occurs, %NULL will be returned. * * If tracefs is not enabled in the kernel, the value -%ENODEV will be * returned. */ struct dentry *tracefs_create_file(const char *name, umode_t mode, struct dentry *parent, void *data, const struct file_operations *fops) { struct tracefs_inode *ti; struct dentry *dentry; struct inode *inode; if (security_locked_down(LOCKDOWN_TRACEFS)) return NULL; if (!(mode & S_IFMT)) mode |= S_IFREG; BUG_ON(!S_ISREG(mode)); dentry = tracefs_start_creating(name, parent); if (IS_ERR(dentry)) return NULL; inode = tracefs_get_inode(dentry->d_sb); if (unlikely(!inode)) return tracefs_failed_creating(dentry); ti = get_tracefs(inode); ti->private = instance_inode(parent, inode); inode->i_mode = mode; inode->i_op = &tracefs_file_inode_operations; inode->i_fop = fops ? fops : &tracefs_file_operations; inode->i_private = data; inode->i_uid = d_inode(dentry->d_parent)->i_uid; inode->i_gid = d_inode(dentry->d_parent)->i_gid; d_instantiate(dentry, inode); fsnotify_create(d_inode(dentry->d_parent), dentry); return tracefs_end_creating(dentry); } static struct dentry *__create_dir(const char *name, struct dentry *parent, const struct inode_operations *ops) { struct tracefs_inode *ti; struct dentry *dentry = tracefs_start_creating(name, parent); struct inode *inode; if (IS_ERR(dentry)) return NULL; inode = tracefs_get_inode(dentry->d_sb); if (unlikely(!inode)) return tracefs_failed_creating(dentry); /* Do not set bits for OTH */ inode->i_mode = S_IFDIR | S_IRWXU | S_IRUSR| S_IRGRP | S_IXUSR | S_IXGRP; inode->i_op = ops; inode->i_fop = &simple_dir_operations; inode->i_uid = d_inode(dentry->d_parent)->i_uid; inode->i_gid = d_inode(dentry->d_parent)->i_gid; ti = get_tracefs(inode); ti->private = instance_inode(parent, inode); /* directory inodes start off with i_nlink == 2 (for "." entry) */ inc_nlink(inode); d_instantiate(dentry, inode); inc_nlink(d_inode(dentry->d_parent)); fsnotify_mkdir(d_inode(dentry->d_parent), dentry); return tracefs_end_creating(dentry); } /** * tracefs_create_dir - create a directory in the tracefs filesystem * @name: a pointer to a string containing the name of the directory to * create. * @parent: a pointer to the parent dentry for this file. This should be a * directory dentry if set. If this parameter is NULL, then the * directory will be created in the root of the tracefs filesystem. * * This function creates a directory in tracefs with the given name. * * This function will return a pointer to a dentry if it succeeds. This * pointer must be passed to the tracefs_remove() function when the file is * to be removed. If an error occurs, %NULL will be returned. * * If tracing is not enabled in the kernel, the value -%ENODEV will be * returned. */ struct dentry *tracefs_create_dir(const char *name, struct dentry *parent) { if (security_locked_down(LOCKDOWN_TRACEFS)) return NULL; return __create_dir(name, parent, &tracefs_dir_inode_operations); } /** * tracefs_create_instance_dir - create the tracing instances directory * @name: The name of the instances directory to create * @parent: The parent directory that the instances directory will exist * @mkdir: The function to call when a mkdir is performed. * @rmdir: The function to call when a rmdir is performed. * * Only one instances directory is allowed. * * The instances directory is special as it allows for mkdir and rmdir * to be done by userspace. When a mkdir or rmdir is performed, the inode * locks are released and the methods passed in (@mkdir and @rmdir) are * called without locks and with the name of the directory being created * within the instances directory. * * Returns the dentry of the instances directory. */ __init struct dentry *tracefs_create_instance_dir(const char *name, struct dentry *parent, int (*mkdir)(const char *name), int (*rmdir)(const char *name)) { struct dentry *dentry; /* Only allow one instance of the instances directory. */ if (WARN_ON(tracefs_ops.mkdir || tracefs_ops.rmdir)) return NULL; dentry = __create_dir(name, parent, &tracefs_instance_dir_inode_operations); if (!dentry) return NULL; tracefs_ops.mkdir = mkdir; tracefs_ops.rmdir = rmdir; return dentry; } static void remove_one(struct dentry *victim) { simple_release_fs(&tracefs_mount, &tracefs_mount_count); } /** * tracefs_remove - recursively removes a directory * @dentry: a pointer to a the dentry of the directory to be removed. * * This function recursively removes a directory tree in tracefs that * was previously created with a call to another tracefs function * (like tracefs_create_file() or variants thereof.) */ void tracefs_remove(struct dentry *dentry) { if (IS_ERR_OR_NULL(dentry)) return; simple_pin_fs(&trace_fs_type, &tracefs_mount, &tracefs_mount_count); simple_recursive_removal(dentry, remove_one); simple_release_fs(&tracefs_mount, &tracefs_mount_count); } /** * tracefs_initialized - Tells whether tracefs has been registered */ bool tracefs_initialized(void) { return tracefs_registered; } static void init_once(void *foo) { struct tracefs_inode *ti = (struct tracefs_inode *) foo; /* inode_init_once() calls memset() on the vfs_inode portion */ inode_init_once(&ti->vfs_inode); /* Zero out the rest */ memset_after(ti, 0, vfs_inode); } static int __init tracefs_init(void) { int retval; tracefs_inode_cachep = kmem_cache_create("tracefs_inode_cache", sizeof(struct tracefs_inode), 0, (SLAB_RECLAIM_ACCOUNT| SLAB_ACCOUNT), init_once); if (!tracefs_inode_cachep) return -ENOMEM; retval = sysfs_create_mount_point(kernel_kobj, "tracing"); if (retval) return -EINVAL; retval = register_filesystem(&trace_fs_type); if (!retval) tracefs_registered = true; return retval; } core_initcall(tracefs_init);