/* * 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. * * 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/kernel.h> #include <linux/sched.h> #include <linux/slab.h> #include <linux/fs.h> #include <linux/file.h> #include <linux/mount.h> #include <linux/namei.h> #include <linux/poll.h> #include <linux/init.h> #include <linux/list.h> #include <linux/inotify.h> #include <linux/syscalls.h> #include <linux/magic.h> #include <asm/ioctls.h> static struct kmem_cache *watch_cachep __read_mostly; static struct kmem_cache *event_cachep __read_mostly; static struct vfsmount *inotify_mnt __read_mostly; /* these are configurable via /proc/sys/fs/inotify/ */ int inotify_max_user_instances __read_mostly; int inotify_max_user_watches __read_mostly; int inotify_max_queued_events __read_mostly; /* * Lock ordering: * * inotify_dev->up_mutex (ensures we don't re-add the same watch) * inode->inotify_mutex (protects inode's watch list) * inotify_handle->mutex (protects inotify_handle's watch list) * inotify_dev->ev_mutex (protects device's event queue) */ /* * Lifetimes of the main data structures: * * inotify_device: Lifetime is managed by reference count, from * sys_inotify_init() until release. Additional references can bump the count * via get_inotify_dev() and drop the count via put_inotify_dev(). * * inotify_user_watch: Lifetime is from create_watch() to the receipt of an * IN_IGNORED event from inotify, or when using IN_ONESHOT, to receipt of the * first event, or to inotify_destroy(). */ /* * struct inotify_device - represents an inotify instance * * This structure is protected by the mutex 'mutex'. */ struct inotify_device { wait_queue_head_t wq; /* wait queue for i/o */ struct mutex ev_mutex; /* protects event queue */ struct mutex up_mutex; /* synchronizes watch updates */ struct list_head events; /* list of queued events */ atomic_t count; /* reference count */ struct user_struct *user; /* user who opened this dev */ struct inotify_handle *ih; /* inotify handle */ struct fasync_struct *fa; /* async notification */ unsigned int queue_size; /* size of the queue (bytes) */ unsigned int event_count; /* number of pending events */ unsigned int max_events; /* maximum number of events */ }; /* * struct inotify_kernel_event - An inotify event, originating from a watch and * queued for user-space. A list of these is attached to each instance of the * device. In read(), this list is walked and all events that can fit in the * buffer are returned. * * Protected by dev->ev_mutex of the device in which we are queued. */ struct inotify_kernel_event { struct inotify_event event; /* the user-space event */ struct list_head list; /* entry in inotify_device's list */ char *name; /* filename, if any */ }; /* * struct inotify_user_watch - our version of an inotify_watch, we add * a reference to the associated inotify_device. */ struct inotify_user_watch { struct inotify_device *dev; /* associated device */ struct inotify_watch wdata; /* inotify watch data */ }; #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 void get_inotify_dev(struct inotify_device *dev) { atomic_inc(&dev->count); } static inline void put_inotify_dev(struct inotify_device *dev) { if (atomic_dec_and_test(&dev->count)) { atomic_dec(&dev->user->inotify_devs); free_uid(dev->user); kfree(dev); } } /* * free_inotify_user_watch - cleans up the watch and its references */ static void free_inotify_user_watch(struct inotify_watch *w) { struct inotify_user_watch *watch; struct inotify_device *dev; watch = container_of(w, struct inotify_user_watch, wdata); dev = watch->dev; atomic_dec(&dev->user->inotify_watches); put_inotify_dev(dev); kmem_cache_free(watch_cachep, watch); } /* * kernel_event - create a new kernel event with the given parameters * * This function can sleep. */ static struct inotify_kernel_event * kernel_event(s32 wd, u32 mask, u32 cookie, const char *name) { struct inotify_kernel_event *kevent; kevent = kmem_cache_alloc(event_cachep, GFP_NOFS); if (unlikely(!kevent)) return NULL; /* we hand this out to user-space, so zero it just in case */ memset(&kevent->event, 0, sizeof(struct inotify_event)); kevent->event.wd = wd; kevent->event.mask = mask; kevent->event.cookie = cookie; INIT_LIST_HEAD(&kevent->list); if (name) { size_t len, rem, event_size = sizeof(struct inotify_event); /* * We need to pad the filename so as to properly align an * array of inotify_event structures. Because the structure is * small and the common case is a small filename, we just round * up to the next multiple of the structure's sizeof. This is * simple and safe for all architectures. */ len = strlen(name) + 1; rem = event_size - len; if (len > event_size) { rem = event_size - (len % event_size); if (len % event_size == 0) rem = 0; } kevent->name = kmalloc(len + rem, GFP_KERNEL); if (unlikely(!kevent->name)) { kmem_cache_free(event_cachep, kevent); return NULL; } memcpy(kevent->name, name, len); if (rem) memset(kevent->name + len, 0, rem); kevent->event.len = len + rem; } else { kevent->event.len = 0; kevent->name = NULL; } return kevent; } /* * inotify_dev_get_event - return the next event in the given dev's queue * * Caller must hold dev->ev_mutex. */ static inline struct inotify_kernel_event * inotify_dev_get_event(struct inotify_device *dev) { return list_entry(dev->events.next, struct inotify_kernel_event, list); } /* * inotify_dev_get_last_event - return the last event in the given dev's queue * * Caller must hold dev->ev_mutex. */ static inline struct inotify_kernel_event * inotify_dev_get_last_event(struct inotify_device *dev) { if (list_empty(&dev->events)) return NULL; return list_entry(dev->events.prev, struct inotify_kernel_event, list); } /* * inotify_dev_queue_event - event handler registered with core inotify, adds * a new event to the given device * * Can sleep (calls kernel_event()). */ static void inotify_dev_queue_event(struct inotify_watch *w, u32 wd, u32 mask, u32 cookie, const char *name, struct inode *ignored) { struct inotify_user_watch *watch; struct inotify_device *dev; struct inotify_kernel_event *kevent, *last; watch = container_of(w, struct inotify_user_watch, wdata); dev = watch->dev; mutex_lock(&dev->ev_mutex); /* we can safely put the watch as we don't reference it while * generating the event */ if (mask & IN_IGNORED || w->mask & IN_ONESHOT) put_inotify_watch(w); /* final put */ /* coalescing: drop this event if it is a dupe of the previous */ last = inotify_dev_get_last_event(dev); if (last && last->event.mask == mask && last->event.wd == wd && last->event.cookie == cookie) { const char *lastname = last->name; if (!name && !lastname) goto out; if (name && lastname && !strcmp(lastname, name)) goto out; } /* the queue overflowed and we already sent the Q_OVERFLOW event */ if (unlikely(dev->event_count > dev->max_events)) goto out; /* if the queue overflows, we need to notify user space */ if (unlikely(dev->event_count == dev->max_events)) kevent = kernel_event(-1, IN_Q_OVERFLOW, cookie, NULL); else kevent = kernel_event(wd, mask, cookie, name); if (unlikely(!kevent)) goto out; /* queue the event and wake up anyone waiting */ dev->event_count++; dev->queue_size += sizeof(struct inotify_event) + kevent->event.len; list_add_tail(&kevent->list, &dev->events); wake_up_interruptible(&dev->wq); kill_fasync(&dev->fa, SIGIO, POLL_IN); out: mutex_unlock(&dev->ev_mutex); } /* * remove_kevent - cleans up and ultimately frees the given kevent * * Caller must hold dev->ev_mutex. */ static void remove_kevent(struct inotify_device *dev, struct inotify_kernel_event *kevent) { list_del(&kevent->list); dev->event_count--; dev->queue_size -= sizeof(struct inotify_event) + kevent->event.len; kfree(kevent->name); kmem_cache_free(event_cachep, kevent); } /* * inotify_dev_event_dequeue - destroy an event on the given device * * Caller must hold dev->ev_mutex. */ static void inotify_dev_event_dequeue(struct inotify_device *dev) { if (!list_empty(&dev->events)) { struct inotify_kernel_event *kevent; kevent = inotify_dev_get_event(dev); remove_kevent(dev, kevent); } } /* * find_inode - resolve a user-given path to a specific inode and return a nd */ static int find_inode(const char __user *dirname, struct nameidata *nd, unsigned flags) { int error; error = __user_walk(dirname, flags, nd); if (error) return error; /* you can only watch an inode if you have read permissions on it */ error = vfs_permission(nd, MAY_READ); if (error) path_release(nd); return error; } /* * create_watch - creates a watch on the given device. * * Callers must hold dev->up_mutex. */ static int create_watch(struct inotify_device *dev, struct inode *inode, u32 mask) { struct inotify_user_watch *watch; int ret; if (atomic_read(&dev->user->inotify_watches) >= inotify_max_user_watches) return -ENOSPC; watch = kmem_cache_alloc(watch_cachep, GFP_KERNEL); if (unlikely(!watch)) return -ENOMEM; /* save a reference to device and bump the count to make it official */ get_inotify_dev(dev); watch->dev = dev; atomic_inc(&dev->user->inotify_watches); inotify_init_watch(&watch->wdata); ret = inotify_add_watch(dev->ih, &watch->wdata, inode, mask); if (ret < 0) free_inotify_user_watch(&watch->wdata); return ret; } /* Device Interface */ static unsigned int inotify_poll(struct file *file, poll_table *wait) { struct inotify_device *dev = file->private_data; int ret = 0; poll_wait(file, &dev->wq, wait); mutex_lock(&dev->ev_mutex); if (!list_empty(&dev->events)) ret = POLLIN | POLLRDNORM; mutex_unlock(&dev->ev_mutex); return ret; } static ssize_t inotify_read(struct file *file, char __user *buf, size_t count, loff_t *pos) { size_t event_size = sizeof (struct inotify_event); struct inotify_device *dev; char __user *start; int ret; DEFINE_WAIT(wait); start = buf; dev = file->private_data; while (1) { int events; prepare_to_wait(&dev->wq, &wait, TASK_INTERRUPTIBLE); mutex_lock(&dev->ev_mutex); events = !list_empty(&dev->events); mutex_unlock(&dev->ev_mutex); if (events) { ret = 0; break; } if (file->f_flags & O_NONBLOCK) { ret = -EAGAIN; break; } if (signal_pending(current)) { ret = -EINTR; break; } schedule(); } finish_wait(&dev->wq, &wait); if (ret) return ret; mutex_lock(&dev->ev_mutex); while (1) { struct inotify_kernel_event *kevent; ret = buf - start; if (list_empty(&dev->events)) break; kevent = inotify_dev_get_event(dev); if (event_size + kevent->event.len > count) { if (ret == 0 && count > 0) { /* * could not get a single event because we * didn't have enough buffer space. */ ret = -EINVAL; } break; } if (copy_to_user(buf, &kevent->event, event_size)) { ret = -EFAULT; break; } buf += event_size; count -= event_size; if (kevent->name) { if (copy_to_user(buf, kevent->name, kevent->event.len)){ ret = -EFAULT; break; } buf += kevent->event.len; count -= kevent->event.len; } remove_kevent(dev, kevent); } mutex_unlock(&dev->ev_mutex); return ret; } static int inotify_fasync(int fd, struct file *file, int on) { struct inotify_device *dev = file->private_data; return fasync_helper(fd, file, on, &dev->fa) >= 0 ? 0 : -EIO; } static int inotify_release(struct inode *ignored, struct file *file) { struct inotify_device *dev = file->private_data; inotify_destroy(dev->ih); /* destroy all of the events on this device */ mutex_lock(&dev->ev_mutex); while (!list_empty(&dev->events)) inotify_dev_event_dequeue(dev); mutex_unlock(&dev->ev_mutex); if (file->f_flags & FASYNC) inotify_fasync(-1, file, 0); /* free this device: the put matching the get in inotify_init() */ put_inotify_dev(dev); return 0; } static long inotify_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { struct inotify_device *dev; void __user *p; int ret = -ENOTTY; dev = file->private_data; p = (void __user *) arg; switch (cmd) { case FIONREAD: ret = put_user(dev->queue_size, (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, }; static const struct inotify_operations inotify_user_ops = { .handle_event = inotify_dev_queue_event, .destroy_watch = free_inotify_user_watch, }; asmlinkage long sys_inotify_init(void) { struct inotify_device *dev; struct inotify_handle *ih; struct user_struct *user; struct file *filp; int fd, ret; fd = get_unused_fd(); if (fd < 0) return fd; filp = get_empty_filp(); if (!filp) { ret = -ENFILE; goto out_put_fd; } user = get_uid(current->user); if (unlikely(atomic_read(&user->inotify_devs) >= inotify_max_user_instances)) { ret = -EMFILE; goto out_free_uid; } dev = kmalloc(sizeof(struct inotify_device), GFP_KERNEL); if (unlikely(!dev)) { ret = -ENOMEM; goto out_free_uid; } ih = inotify_init(&inotify_user_ops); if (unlikely(IS_ERR(ih))) { ret = PTR_ERR(ih); goto out_free_dev; } dev->ih = ih; dev->fa = NULL; 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; filp->private_data = dev; INIT_LIST_HEAD(&dev->events); init_waitqueue_head(&dev->wq); mutex_init(&dev->ev_mutex); mutex_init(&dev->up_mutex); dev->event_count = 0; dev->queue_size = 0; dev->max_events = inotify_max_queued_events; dev->user = user; atomic_set(&dev->count, 0); get_inotify_dev(dev); atomic_inc(&user->inotify_devs); fd_install(fd, filp); return fd; out_free_dev: kfree(dev); out_free_uid: free_uid(user); put_filp(filp); out_put_fd: put_unused_fd(fd); return ret; } asmlinkage long sys_inotify_add_watch(int fd, const char __user *path, u32 mask) { struct inode *inode; struct inotify_device *dev; struct nameidata nd; 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 = find_inode(path, &nd, flags); if (unlikely(ret)) goto fput_and_out; /* inode held in place by reference to nd; dev by fget on fd */ inode = nd.dentry->d_inode; dev = filp->private_data; mutex_lock(&dev->up_mutex); ret = inotify_find_update_watch(dev->ih, inode, mask); if (ret == -ENOENT) ret = create_watch(dev, inode, mask); mutex_unlock(&dev->up_mutex); path_release(&nd); fput_and_out: fput_light(filp, fput_needed); return ret; } asmlinkage long sys_inotify_rm_watch(int fd, u32 wd) { struct file *filp; struct inotify_device *dev; int ret, 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; } dev = filp->private_data; /* we free our watch data when we get IN_IGNORED */ ret = inotify_rm_wd(dev->ih, wd); 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_max_queued_events = 16384; inotify_max_user_instances = 128; inotify_max_user_watches = 8192; watch_cachep = kmem_cache_create("inotify_watch_cache", sizeof(struct inotify_user_watch), 0, SLAB_PANIC, NULL); event_cachep = kmem_cache_create("inotify_event_cache", sizeof(struct inotify_kernel_event), 0, SLAB_PANIC, NULL); return 0; } module_init(inotify_user_setup);