blob: 982a412ac5bc95d7665bc15d48b1e529ec0c5b20 [file] [log] [blame]
/*
* 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;
/* this just sits here and wastes global memory. used to just pad userspace messages with zeros */
static struct inotify_event nul_inotify_event;
/* 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;
static struct fsnotify_event *inotify_ignored_event;
/*
* 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);
event_size += roundup(event->name_len, 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;
/* 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 */
name_len = roundup(event->name_len, 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 from nul_inotify_event */
if (copy_to_user(buf, &nul_inotify_event, 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;
fsnotify_clear_marks_by_group(group);
/* free this group, matching get was inotify_init->fsnotify_obtain_group */
fsnotify_put_group(group);
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);
send_len += roundup(event->name_len,
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;
}
/*
* When, for whatever reason, inotify is done with a mark (or what used to be a
* watch) we need to remove that watch from the idr and we need to send IN_IGNORED
* for the given wd.
*
* There is a bit of recursion here. The loop looks like:
* inotify_destroy_mark_entry -> fsnotify_destroy_mark_by_entry ->
* inotify_freeing_mark -> inotify_destory_mark_entry -> restart
* But the loop is broken in 2 places. fsnotify_destroy_mark_by_entry sets
* entry->group = NULL before the call to inotify_freeing_mark, so the if (egroup)
* test below will not call back to fsnotify again. But even if that test wasn't
* there this would still be safe since fsnotify_destroy_mark_by_entry() is
* safe from recursion.
*/
void inotify_destroy_mark_entry(struct fsnotify_mark_entry *entry, struct fsnotify_group *group)
{
struct inotify_inode_mark_entry *ientry;
struct inotify_event_private_data *event_priv;
struct fsnotify_event_private_data *fsn_event_priv;
struct fsnotify_group *egroup;
struct idr *idr;
spin_lock(&entry->lock);
egroup = entry->group;
/* if egroup we aren't really done and something might still send events
* for this inode, on the callback we'll send the IN_IGNORED */
if (egroup) {
spin_unlock(&entry->lock);
fsnotify_destroy_mark_by_entry(entry);
return;
}
spin_unlock(&entry->lock);
ientry = container_of(entry, struct inotify_inode_mark_entry, fsn_entry);
event_priv = kmem_cache_alloc(event_priv_cachep, GFP_KERNEL);
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;
fsnotify_add_notify_event(group, inotify_ignored_event, fsn_event_priv);
/* did the private data get added? */
if (list_empty(&fsn_event_priv->event_list))
inotify_free_event_priv(fsn_event_priv);
skip_send_ignore:
/* remove this entry from the idr */
spin_lock(&group->inotify_data.idr_lock);
idr = &group->inotify_data.idr;
idr_remove(idr, ientry->wd);
spin_unlock(&group->inotify_data.idr_lock);
/* removed from idr, drop that reference */
fsnotify_put_mark(entry);
}
/* 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_watch(struct fsnotify_group *group, struct inode *inode, u32 arg)
{
struct fsnotify_mark_entry *entry = NULL;
struct inotify_inode_mark_entry *ientry;
int ret = 0;
int add = (arg & IN_MASK_ADD);
__u32 mask;
__u32 old_mask, new_mask;
/* don't allow invalid bits: we don't want flags set */
mask = inotify_arg_to_mask(arg);
if (unlikely(!mask))
return -EINVAL;
ientry = kmem_cache_alloc(inotify_inode_mark_cachep, GFP_KERNEL);
if (unlikely(!ientry))
return -ENOMEM;
/* we set the mask at the end after attaching it */
fsnotify_init_mark(&ientry->fsn_entry, inotify_free_mark);
ientry->wd = 0;
find_entry:
spin_lock(&inode->i_lock);
entry = fsnotify_find_mark_entry(group, inode);
spin_unlock(&inode->i_lock);
if (entry) {
kmem_cache_free(inotify_inode_mark_cachep, ientry);
ientry = container_of(entry, struct inotify_inode_mark_entry, fsn_entry);
} else {
if (atomic_read(&group->inotify_data.user->inotify_watches) >= inotify_max_user_watches) {
ret = -ENOSPC;
goto out_err;
}
ret = fsnotify_add_mark(&ientry->fsn_entry, group, inode);
if (ret == -EEXIST)
goto find_entry;
else if (ret)
goto out_err;
entry = &ientry->fsn_entry;
retry:
ret = -ENOMEM;
if (unlikely(!idr_pre_get(&group->inotify_data.idr, GFP_KERNEL)))
goto out_err;
spin_lock(&group->inotify_data.idr_lock);
/* if entry is added to the idr we keep the reference obtained
* through fsnotify_mark_add. remember to drop this reference
* when entry is removed from idr */
ret = idr_get_new_above(&group->inotify_data.idr, entry,
++group->inotify_data.last_wd,
&ientry->wd);
spin_unlock(&group->inotify_data.idr_lock);
if (ret) {
if (ret == -EAGAIN)
goto retry;
goto out_err;
}
atomic_inc(&group->inotify_data.user->inotify_watches);
}
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 ientry->wd;
out_err:
/* see this isn't supposed to happen, just kill the watch */
if (entry) {
fsnotify_destroy_mark_by_entry(entry);
fsnotify_put_mark(entry);
}
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 = 0;
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);
inotify_destroy_mark_entry(entry, group);
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_ignored_event = fsnotify_create_event(NULL, FS_IN_IGNORED, NULL, FSNOTIFY_EVENT_NONE, NULL, 0);
if (!inotify_ignored_event)
panic("unable to allocate the inotify ignored event\n");
inotify_max_queued_events = 16384;
inotify_max_user_instances = 128;
inotify_max_user_watches = 8192;
return 0;
}
module_init(inotify_user_setup);