/* * fs/inotify_user.c - inotify support for userspace * * Authors: * John McCutchan <ttb@tentacle.dhs.org> * Robert Love <rml@novell.com> * * Copyright (C) 2005 John McCutchan * Copyright 2006 Hewlett-Packard Development Company, L.P. * * Copyright (C) 2009 Eric Paris <Red Hat Inc> * inotify was largely rewriten to make use of the fsnotify infrastructure * * This program is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License as published by the * Free Software Foundation; either version 2, or (at your option) any * later version. * * This program is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. */ #include <linux/file.h> #include <linux/fs.h> /* struct inode */ #include <linux/fsnotify_backend.h> #include <linux/idr.h> #include <linux/init.h> /* module_init */ #include <linux/inotify.h> #include <linux/kernel.h> /* roundup() */ #include <linux/magic.h> /* superblock magic number */ #include <linux/mount.h> /* mntget */ #include <linux/namei.h> /* LOOKUP_FOLLOW */ #include <linux/path.h> /* struct path */ #include <linux/sched.h> /* struct user */ #include <linux/slab.h> /* struct kmem_cache */ #include <linux/syscalls.h> #include <linux/types.h> #include <linux/uaccess.h> #include <linux/poll.h> #include <linux/wait.h> #include "inotify.h" #include <asm/ioctls.h> static struct vfsmount *inotify_mnt __read_mostly; /* these are configurable via /proc/sys/fs/inotify/ */ static int inotify_max_user_instances __read_mostly; static int inotify_max_queued_events __read_mostly; int inotify_max_user_watches __read_mostly; static struct kmem_cache *inotify_inode_mark_cachep __read_mostly; struct kmem_cache *event_priv_cachep __read_mostly; /* * When inotify registers a new group it increments this and uses that * value as an offset to set the fsnotify group "name" and priority. */ static atomic_t inotify_grp_num; #ifdef CONFIG_SYSCTL #include <linux/sysctl.h> static int zero; ctl_table inotify_table[] = { { .ctl_name = INOTIFY_MAX_USER_INSTANCES, .procname = "max_user_instances", .data = &inotify_max_user_instances, .maxlen = sizeof(int), .mode = 0644, .proc_handler = &proc_dointvec_minmax, .strategy = &sysctl_intvec, .extra1 = &zero, }, { .ctl_name = INOTIFY_MAX_USER_WATCHES, .procname = "max_user_watches", .data = &inotify_max_user_watches, .maxlen = sizeof(int), .mode = 0644, .proc_handler = &proc_dointvec_minmax, .strategy = &sysctl_intvec, .extra1 = &zero, }, { .ctl_name = INOTIFY_MAX_QUEUED_EVENTS, .procname = "max_queued_events", .data = &inotify_max_queued_events, .maxlen = sizeof(int), .mode = 0644, .proc_handler = &proc_dointvec_minmax, .strategy = &sysctl_intvec, .extra1 = &zero }, { .ctl_name = 0 } }; #endif /* CONFIG_SYSCTL */ static inline __u32 inotify_arg_to_mask(u32 arg) { __u32 mask; /* everything should accept their own ignored and cares about children */ mask = (FS_IN_IGNORED | FS_EVENT_ON_CHILD); /* mask off the flags used to open the fd */ mask |= (arg & (IN_ALL_EVENTS | IN_ONESHOT)); return mask; } static inline u32 inotify_mask_to_arg(__u32 mask) { return mask & (IN_ALL_EVENTS | IN_ISDIR | IN_UNMOUNT | IN_IGNORED | IN_Q_OVERFLOW); } /* intofiy userspace file descriptor functions */ static unsigned int inotify_poll(struct file *file, poll_table *wait) { struct fsnotify_group *group = file->private_data; int ret = 0; poll_wait(file, &group->notification_waitq, wait); mutex_lock(&group->notification_mutex); if (!fsnotify_notify_queue_is_empty(group)) ret = POLLIN | POLLRDNORM; mutex_unlock(&group->notification_mutex); return ret; } /* * Get an inotify_kernel_event if one exists and is small * enough to fit in "count". Return an error pointer if * not large enough. * * Called with the group->notification_mutex held. */ static struct fsnotify_event *get_one_event(struct fsnotify_group *group, size_t count) { size_t event_size = sizeof(struct inotify_event); struct fsnotify_event *event; if (fsnotify_notify_queue_is_empty(group)) return NULL; event = fsnotify_peek_notify_event(group); if (event->name_len) event_size += roundup(event->name_len + 1, event_size); if (event_size > count) return ERR_PTR(-EINVAL); /* held the notification_mutex the whole time, so this is the * same event we peeked above */ fsnotify_remove_notify_event(group); return event; } /* * Copy an event to user space, returning how much we copied. * * We already checked that the event size is smaller than the * buffer we had in "get_one_event()" above. */ static ssize_t copy_event_to_user(struct fsnotify_group *group, struct fsnotify_event *event, char __user *buf) { struct inotify_event inotify_event; struct fsnotify_event_private_data *fsn_priv; struct inotify_event_private_data *priv; size_t event_size = sizeof(struct inotify_event); size_t name_len = 0; /* we get the inotify watch descriptor from the event private data */ spin_lock(&event->lock); fsn_priv = fsnotify_remove_priv_from_event(group, event); spin_unlock(&event->lock); if (!fsn_priv) inotify_event.wd = -1; else { priv = container_of(fsn_priv, struct inotify_event_private_data, fsnotify_event_priv_data); inotify_event.wd = priv->wd; inotify_free_event_priv(fsn_priv); } /* * round up event->name_len so it is a multiple of event_size * plus an extra byte for the terminating '\0'. */ if (event->name_len) name_len = roundup(event->name_len + 1, event_size); inotify_event.len = name_len; inotify_event.mask = inotify_mask_to_arg(event->mask); inotify_event.cookie = event->sync_cookie; /* send the main event */ if (copy_to_user(buf, &inotify_event, event_size)) return -EFAULT; buf += event_size; /* * fsnotify only stores the pathname, so here we have to send the pathname * and then pad that pathname out to a multiple of sizeof(inotify_event) * with zeros. I get my zeros from the nul_inotify_event. */ if (name_len) { unsigned int len_to_zero = name_len - event->name_len; /* copy the path name */ if (copy_to_user(buf, event->file_name, event->name_len)) return -EFAULT; buf += event->name_len; /* fill userspace with 0's */ if (clear_user(buf, len_to_zero)) return -EFAULT; buf += len_to_zero; event_size += name_len; } return event_size; } static ssize_t inotify_read(struct file *file, char __user *buf, size_t count, loff_t *pos) { struct fsnotify_group *group; struct fsnotify_event *kevent; char __user *start; int ret; DEFINE_WAIT(wait); start = buf; group = file->private_data; while (1) { prepare_to_wait(&group->notification_waitq, &wait, TASK_INTERRUPTIBLE); mutex_lock(&group->notification_mutex); kevent = get_one_event(group, count); mutex_unlock(&group->notification_mutex); if (kevent) { ret = PTR_ERR(kevent); if (IS_ERR(kevent)) break; ret = copy_event_to_user(group, kevent, buf); fsnotify_put_event(kevent); if (ret < 0) break; buf += ret; count -= ret; continue; } ret = -EAGAIN; if (file->f_flags & O_NONBLOCK) break; ret = -EINTR; if (signal_pending(current)) break; if (start != buf) break; schedule(); } finish_wait(&group->notification_waitq, &wait); if (start != buf && ret != -EFAULT) ret = buf - start; return ret; } static int inotify_fasync(int fd, struct file *file, int on) { struct fsnotify_group *group = file->private_data; return fasync_helper(fd, file, on, &group->inotify_data.fa) >= 0 ? 0 : -EIO; } static int inotify_release(struct inode *ignored, struct file *file) { struct fsnotify_group *group = file->private_data; struct user_struct *user = group->inotify_data.user; fsnotify_clear_marks_by_group(group); /* free this group, matching get was inotify_init->fsnotify_obtain_group */ fsnotify_put_group(group); atomic_dec(&user->inotify_devs); return 0; } static long inotify_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { struct fsnotify_group *group; struct fsnotify_event_holder *holder; struct fsnotify_event *event; void __user *p; int ret = -ENOTTY; size_t send_len = 0; group = file->private_data; p = (void __user *) arg; switch (cmd) { case FIONREAD: mutex_lock(&group->notification_mutex); list_for_each_entry(holder, &group->notification_list, event_list) { event = holder->event; send_len += sizeof(struct inotify_event); if (event->name_len) send_len += roundup(event->name_len + 1, sizeof(struct inotify_event)); } mutex_unlock(&group->notification_mutex); ret = put_user(send_len, (int __user *) p); break; } return ret; } static const struct file_operations inotify_fops = { .poll = inotify_poll, .read = inotify_read, .fasync = inotify_fasync, .release = inotify_release, .unlocked_ioctl = inotify_ioctl, .compat_ioctl = inotify_ioctl, }; /* * find_inode - resolve a user-given path to a specific inode */ static int inotify_find_inode(const char __user *dirname, struct path *path, unsigned flags) { int error; error = user_path_at(AT_FDCWD, dirname, flags, path); if (error) return error; /* you can only watch an inode if you have read permissions on it */ error = inode_permission(path->dentry->d_inode, MAY_READ); if (error) path_put(path); return error; } /* * Remove the mark from the idr (if present) and drop the reference * on the mark because it was in the idr. */ static void inotify_remove_from_idr(struct fsnotify_group *group, struct inotify_inode_mark_entry *ientry) { struct idr *idr; struct fsnotify_mark_entry *entry; struct inotify_inode_mark_entry *found_ientry; int wd; spin_lock(&group->inotify_data.idr_lock); idr = &group->inotify_data.idr; wd = ientry->wd; if (wd == -1) goto out; entry = idr_find(&group->inotify_data.idr, wd); if (unlikely(!entry)) goto out; found_ientry = container_of(entry, struct inotify_inode_mark_entry, fsn_entry); if (unlikely(found_ientry != ientry)) { /* We found an entry in the idr with the right wd, but it's * not the entry we were told to remove. eparis seriously * fucked up somewhere. */ WARN_ON(1); ientry->wd = -1; goto out; } /* One ref for being in the idr, one ref held by the caller */ BUG_ON(atomic_read(&entry->refcnt) < 2); idr_remove(idr, wd); ientry->wd = -1; /* removed from the idr, drop that ref */ fsnotify_put_mark(entry); out: spin_unlock(&group->inotify_data.idr_lock); } /* * Send IN_IGNORED for this wd, remove this wd from the idr. */ void inotify_ignored_and_remove_idr(struct fsnotify_mark_entry *entry, struct fsnotify_group *group) { struct inotify_inode_mark_entry *ientry; struct fsnotify_event *ignored_event; struct inotify_event_private_data *event_priv; struct fsnotify_event_private_data *fsn_event_priv; int ret; ignored_event = fsnotify_create_event(NULL, FS_IN_IGNORED, NULL, FSNOTIFY_EVENT_NONE, NULL, 0, GFP_NOFS); if (!ignored_event) return; ientry = container_of(entry, struct inotify_inode_mark_entry, fsn_entry); event_priv = kmem_cache_alloc(event_priv_cachep, GFP_NOFS); if (unlikely(!event_priv)) goto skip_send_ignore; fsn_event_priv = &event_priv->fsnotify_event_priv_data; fsn_event_priv->group = group; event_priv->wd = ientry->wd; ret = fsnotify_add_notify_event(group, ignored_event, fsn_event_priv); if (ret) inotify_free_event_priv(fsn_event_priv); skip_send_ignore: /* matches the reference taken when the event was created */ fsnotify_put_event(ignored_event); /* remove this entry from the idr */ inotify_remove_from_idr(group, ientry); atomic_dec(&group->inotify_data.user->inotify_watches); } /* ding dong the mark is dead */ static void inotify_free_mark(struct fsnotify_mark_entry *entry) { struct inotify_inode_mark_entry *ientry = (struct inotify_inode_mark_entry *)entry; kmem_cache_free(inotify_inode_mark_cachep, ientry); } static int inotify_update_existing_watch(struct fsnotify_group *group, struct inode *inode, u32 arg) { struct fsnotify_mark_entry *entry; struct inotify_inode_mark_entry *ientry; __u32 old_mask, new_mask; __u32 mask; int add = (arg & IN_MASK_ADD); int ret; /* don't allow invalid bits: we don't want flags set */ mask = inotify_arg_to_mask(arg); if (unlikely(!mask)) return -EINVAL; spin_lock(&inode->i_lock); entry = fsnotify_find_mark_entry(group, inode); spin_unlock(&inode->i_lock); if (!entry) return -ENOENT; ientry = container_of(entry, struct inotify_inode_mark_entry, fsn_entry); spin_lock(&entry->lock); old_mask = entry->mask; if (add) { entry->mask |= mask; new_mask = entry->mask; } else { entry->mask = mask; new_mask = entry->mask; } spin_unlock(&entry->lock); if (old_mask != new_mask) { /* more bits in old than in new? */ int dropped = (old_mask & ~new_mask); /* more bits in this entry than the inode's mask? */ int do_inode = (new_mask & ~inode->i_fsnotify_mask); /* more bits in this entry than the group? */ int do_group = (new_mask & ~group->mask); /* update the inode with this new entry */ if (dropped || do_inode) fsnotify_recalc_inode_mask(inode); /* update the group mask with the new mask */ if (dropped || do_group) fsnotify_recalc_group_mask(group); } /* return the wd */ ret = ientry->wd; /* match the get from fsnotify_find_mark_entry() */ fsnotify_put_mark(entry); return ret; } static int inotify_new_watch(struct fsnotify_group *group, struct inode *inode, u32 arg) { struct inotify_inode_mark_entry *tmp_ientry; __u32 mask; int ret; /* don't allow invalid bits: we don't want flags set */ mask = inotify_arg_to_mask(arg); if (unlikely(!mask)) return -EINVAL; tmp_ientry = kmem_cache_alloc(inotify_inode_mark_cachep, GFP_KERNEL); if (unlikely(!tmp_ientry)) return -ENOMEM; fsnotify_init_mark(&tmp_ientry->fsn_entry, inotify_free_mark); tmp_ientry->fsn_entry.mask = mask; tmp_ientry->wd = -1; ret = -ENOSPC; if (atomic_read(&group->inotify_data.user->inotify_watches) >= inotify_max_user_watches) goto out_err; retry: ret = -ENOMEM; if (unlikely(!idr_pre_get(&group->inotify_data.idr, GFP_KERNEL))) goto out_err; spin_lock(&group->inotify_data.idr_lock); ret = idr_get_new_above(&group->inotify_data.idr, &tmp_ientry->fsn_entry, group->inotify_data.last_wd, &tmp_ientry->wd); spin_unlock(&group->inotify_data.idr_lock); if (ret) { /* idr was out of memory allocate and try again */ if (ret == -EAGAIN) goto retry; goto out_err; } /* we put the mark on the idr, take a reference */ fsnotify_get_mark(&tmp_ientry->fsn_entry); /* we are on the idr, now get on the inode */ ret = fsnotify_add_mark(&tmp_ientry->fsn_entry, group, inode); if (ret) { /* we failed to get on the inode, get off the idr */ inotify_remove_from_idr(group, tmp_ientry); goto out_err; } /* update the idr hint, who cares about races, it's just a hint */ group->inotify_data.last_wd = tmp_ientry->wd; /* increment the number of watches the user has */ atomic_inc(&group->inotify_data.user->inotify_watches); /* return the watch descriptor for this new entry */ ret = tmp_ientry->wd; /* match the ref from fsnotify_init_markentry() */ fsnotify_put_mark(&tmp_ientry->fsn_entry); /* if this mark added a new event update the group mask */ if (mask & ~group->mask) fsnotify_recalc_group_mask(group); out_err: if (ret < 0) kmem_cache_free(inotify_inode_mark_cachep, tmp_ientry); return ret; } static int inotify_update_watch(struct fsnotify_group *group, struct inode *inode, u32 arg) { int ret = 0; retry: /* try to update and existing watch with the new arg */ ret = inotify_update_existing_watch(group, inode, arg); /* no mark present, try to add a new one */ if (ret == -ENOENT) ret = inotify_new_watch(group, inode, arg); /* * inotify_new_watch could race with another thread which did an * inotify_new_watch between the update_existing and the add watch * here, go back and try to update an existing mark again. */ if (ret == -EEXIST) goto retry; return ret; } static struct fsnotify_group *inotify_new_group(struct user_struct *user, unsigned int max_events) { struct fsnotify_group *group; unsigned int grp_num; /* fsnotify_obtain_group took a reference to group, we put this when we kill the file in the end */ grp_num = (INOTIFY_GROUP_NUM - atomic_inc_return(&inotify_grp_num)); group = fsnotify_obtain_group(grp_num, 0, &inotify_fsnotify_ops); if (IS_ERR(group)) return group; group->max_events = max_events; spin_lock_init(&group->inotify_data.idr_lock); idr_init(&group->inotify_data.idr); group->inotify_data.last_wd = 1; group->inotify_data.user = user; group->inotify_data.fa = NULL; return group; } /* inotify syscalls */ SYSCALL_DEFINE1(inotify_init1, int, flags) { struct fsnotify_group *group; struct user_struct *user; struct file *filp; int fd, ret; /* Check the IN_* constants for consistency. */ BUILD_BUG_ON(IN_CLOEXEC != O_CLOEXEC); BUILD_BUG_ON(IN_NONBLOCK != O_NONBLOCK); if (flags & ~(IN_CLOEXEC | IN_NONBLOCK)) return -EINVAL; fd = get_unused_fd_flags(flags & O_CLOEXEC); if (fd < 0) return fd; filp = get_empty_filp(); if (!filp) { ret = -ENFILE; goto out_put_fd; } user = get_current_user(); if (unlikely(atomic_read(&user->inotify_devs) >= inotify_max_user_instances)) { ret = -EMFILE; goto out_free_uid; } /* fsnotify_obtain_group took a reference to group, we put this when we kill the file in the end */ group = inotify_new_group(user, inotify_max_queued_events); if (IS_ERR(group)) { ret = PTR_ERR(group); goto out_free_uid; } filp->f_op = &inotify_fops; filp->f_path.mnt = mntget(inotify_mnt); filp->f_path.dentry = dget(inotify_mnt->mnt_root); filp->f_mapping = filp->f_path.dentry->d_inode->i_mapping; filp->f_mode = FMODE_READ; filp->f_flags = O_RDONLY | (flags & O_NONBLOCK); filp->private_data = group; atomic_inc(&user->inotify_devs); fd_install(fd, filp); return fd; out_free_uid: free_uid(user); put_filp(filp); out_put_fd: put_unused_fd(fd); return ret; } SYSCALL_DEFINE0(inotify_init) { return sys_inotify_init1(0); } SYSCALL_DEFINE3(inotify_add_watch, int, fd, const char __user *, pathname, u32, mask) { struct fsnotify_group *group; struct inode *inode; struct path path; struct file *filp; int ret, fput_needed; unsigned flags = 0; filp = fget_light(fd, &fput_needed); if (unlikely(!filp)) return -EBADF; /* verify that this is indeed an inotify instance */ if (unlikely(filp->f_op != &inotify_fops)) { ret = -EINVAL; goto fput_and_out; } if (!(mask & IN_DONT_FOLLOW)) flags |= LOOKUP_FOLLOW; if (mask & IN_ONLYDIR) flags |= LOOKUP_DIRECTORY; ret = inotify_find_inode(pathname, &path, flags); if (ret) goto fput_and_out; /* inode held in place by reference to path; group by fget on fd */ inode = path.dentry->d_inode; group = filp->private_data; /* create/update an inode mark */ ret = inotify_update_watch(group, inode, mask); if (unlikely(ret)) goto path_put_and_out; path_put_and_out: path_put(&path); fput_and_out: fput_light(filp, fput_needed); return ret; } SYSCALL_DEFINE2(inotify_rm_watch, int, fd, __s32, wd) { struct fsnotify_group *group; struct fsnotify_mark_entry *entry; struct file *filp; int ret = 0, fput_needed; filp = fget_light(fd, &fput_needed); if (unlikely(!filp)) return -EBADF; /* verify that this is indeed an inotify instance */ if (unlikely(filp->f_op != &inotify_fops)) { ret = -EINVAL; goto out; } group = filp->private_data; spin_lock(&group->inotify_data.idr_lock); entry = idr_find(&group->inotify_data.idr, wd); if (unlikely(!entry)) { spin_unlock(&group->inotify_data.idr_lock); ret = -EINVAL; goto out; } fsnotify_get_mark(entry); spin_unlock(&group->inotify_data.idr_lock); fsnotify_destroy_mark_by_entry(entry); fsnotify_put_mark(entry); out: fput_light(filp, fput_needed); return ret; } static int inotify_get_sb(struct file_system_type *fs_type, int flags, const char *dev_name, void *data, struct vfsmount *mnt) { return get_sb_pseudo(fs_type, "inotify", NULL, INOTIFYFS_SUPER_MAGIC, mnt); } static struct file_system_type inotify_fs_type = { .name = "inotifyfs", .get_sb = inotify_get_sb, .kill_sb = kill_anon_super, }; /* * inotify_user_setup - Our initialization function. Note that we cannnot return * error because we have compiled-in VFS hooks. So an (unlikely) failure here * must result in panic(). */ static int __init inotify_user_setup(void) { int ret; ret = register_filesystem(&inotify_fs_type); if (unlikely(ret)) panic("inotify: register_filesystem returned %d!\n", ret); inotify_mnt = kern_mount(&inotify_fs_type); if (IS_ERR(inotify_mnt)) panic("inotify: kern_mount ret %ld!\n", PTR_ERR(inotify_mnt)); inotify_inode_mark_cachep = KMEM_CACHE(inotify_inode_mark_entry, SLAB_PANIC); event_priv_cachep = KMEM_CACHE(inotify_event_private_data, SLAB_PANIC); inotify_max_queued_events = 16384; inotify_max_user_instances = 128; inotify_max_user_watches = 8192; return 0; } module_init(inotify_user_setup);