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#include <linux/fanotify.h>
#include <linux/fcntl.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/anon_inodes.h>
#include <linux/fsnotify_backend.h>
#include <linux/init.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/poll.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/types.h>
#include <linux/uaccess.h>
#include <asm/ioctls.h>
extern const struct fsnotify_ops fanotify_fsnotify_ops;
static struct kmem_cache *fanotify_mark_cache __read_mostly;
/*
* Get an fsnotify notification event if one exists and is small
* enough to fit in "count". Return an error pointer if the count
* is not large enough.
*
* Called with the group->notification_mutex held.
*/
static struct fsnotify_event *get_one_event(struct fsnotify_group *group,
size_t count)
{
BUG_ON(!mutex_is_locked(&group->notification_mutex));
pr_debug("%s: group=%p count=%zd\n", __func__, group, count);
if (fsnotify_notify_queue_is_empty(group))
return NULL;
if (FAN_EVENT_METADATA_LEN > count)
return ERR_PTR(-EINVAL);
/* held the notification_mutex the whole time, so this is the
* same event we peeked above */
return fsnotify_remove_notify_event(group);
}
static int create_fd(struct fsnotify_group *group, struct fsnotify_event *event)
{
int client_fd;
struct dentry *dentry;
struct vfsmount *mnt;
struct file *new_file;
pr_debug("%s: group=%p event=%p\n", __func__, group, event);
client_fd = get_unused_fd();
if (client_fd < 0)
return client_fd;
if (event->data_type != FSNOTIFY_EVENT_PATH) {
WARN_ON(1);
put_unused_fd(client_fd);
return -EINVAL;
}
/*
* we need a new file handle for the userspace program so it can read even if it was
* originally opened O_WRONLY.
*/
dentry = dget(event->path.dentry);
mnt = mntget(event->path.mnt);
/* it's possible this event was an overflow event. in that case dentry and mnt
* are NULL; That's fine, just don't call dentry open */
if (dentry && mnt)
new_file = dentry_open(dentry, mnt,
O_RDONLY | O_LARGEFILE | FMODE_NONOTIFY,
current_cred());
else
new_file = ERR_PTR(-EOVERFLOW);
if (IS_ERR(new_file)) {
/*
* we still send an event even if we can't open the file. this
* can happen when say tasks are gone and we try to open their
* /proc files or we try to open a WRONLY file like in sysfs
* we just send the errno to userspace since there isn't much
* else we can do.
*/
put_unused_fd(client_fd);
client_fd = PTR_ERR(new_file);
} else {
fd_install(client_fd, new_file);
}
return client_fd;
}
static ssize_t fill_event_metadata(struct fsnotify_group *group,
struct fanotify_event_metadata *metadata,
struct fsnotify_event *event)
{
pr_debug("%s: group=%p metadata=%p event=%p\n", __func__,
group, metadata, event);
metadata->event_len = FAN_EVENT_METADATA_LEN;
metadata->vers = FANOTIFY_METADATA_VERSION;
metadata->mask = event->mask & FAN_ALL_OUTGOING_EVENTS;
metadata->pid = pid_vnr(event->tgid);
metadata->fd = create_fd(group, event);
return metadata->fd;
}
static ssize_t copy_event_to_user(struct fsnotify_group *group,
struct fsnotify_event *event,
char __user *buf)
{
struct fanotify_event_metadata fanotify_event_metadata;
int ret;
pr_debug("%s: group=%p event=%p\n", __func__, group, event);
ret = fill_event_metadata(group, &fanotify_event_metadata, event);
if (ret < 0)
return ret;
if (copy_to_user(buf, &fanotify_event_metadata, FAN_EVENT_METADATA_LEN))
return -EFAULT;
return FAN_EVENT_METADATA_LEN;
}
/* intofiy userspace file descriptor functions */
static unsigned int fanotify_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;
}
static ssize_t fanotify_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;
pr_debug("%s: group=%p\n", __func__, group);
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 fanotify_release(struct inode *ignored, struct file *file)
{
struct fsnotify_group *group = file->private_data;
pr_debug("%s: file=%p group=%p\n", __func__, file, group);
/* matches the fanotify_init->fsnotify_alloc_group */
fsnotify_put_group(group);
return 0;
}
static long fanotify_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
struct fsnotify_group *group;
struct fsnotify_event_holder *holder;
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)
send_len += FAN_EVENT_METADATA_LEN;
mutex_unlock(&group->notification_mutex);
ret = put_user(send_len, (int __user *) p);
break;
}
return ret;
}
static const struct file_operations fanotify_fops = {
.poll = fanotify_poll,
.read = fanotify_read,
.fasync = NULL,
.release = fanotify_release,
.unlocked_ioctl = fanotify_ioctl,
.compat_ioctl = fanotify_ioctl,
};
static void fanotify_free_mark(struct fsnotify_mark *fsn_mark)
{
kmem_cache_free(fanotify_mark_cache, fsn_mark);
}
static int fanotify_find_path(int dfd, const char __user *filename,
struct path *path, unsigned int flags)
{
int ret;
pr_debug("%s: dfd=%d filename=%p flags=%x\n", __func__,
dfd, filename, flags);
if (filename == NULL) {
struct file *file;
int fput_needed;
ret = -EBADF;
file = fget_light(dfd, &fput_needed);
if (!file)
goto out;
ret = -ENOTDIR;
if ((flags & FAN_MARK_ONLYDIR) &&
!(S_ISDIR(file->f_path.dentry->d_inode->i_mode))) {
fput_light(file, fput_needed);
goto out;
}
*path = file->f_path;
path_get(path);
fput_light(file, fput_needed);
} else {
unsigned int lookup_flags = 0;
if (!(flags & FAN_MARK_DONT_FOLLOW))
lookup_flags |= LOOKUP_FOLLOW;
if (flags & FAN_MARK_ONLYDIR)
lookup_flags |= LOOKUP_DIRECTORY;
ret = user_path_at(dfd, filename, lookup_flags, path);
if (ret)
goto out;
}
/* you can only watch an inode if you have read permissions on it */
ret = inode_permission(path->dentry->d_inode, MAY_READ);
if (ret)
path_put(path);
out:
return ret;
}
static __u32 fanotify_mark_remove_from_mask(struct fsnotify_mark *fsn_mark, __u32 mask)
{
__u32 oldmask;
spin_lock(&fsn_mark->lock);
oldmask = fsn_mark->mask;
fsn_mark->mask = oldmask & ~mask;
spin_unlock(&fsn_mark->lock);
if (!(oldmask & ~mask))
fsnotify_destroy_mark(fsn_mark);
return mask & oldmask;
}
static int fanotify_remove_vfsmount_mark(struct fsnotify_group *group,
struct vfsmount *mnt, __u32 mask)
{
struct fsnotify_mark *fsn_mark = NULL;
__u32 removed;
fsn_mark = fsnotify_find_vfsmount_mark(group, mnt);
if (!fsn_mark)
return -ENOENT;
removed = fanotify_mark_remove_from_mask(fsn_mark, mask);
fsnotify_put_mark(fsn_mark);
if (removed & group->mask)
fsnotify_recalc_group_mask(group);
if (removed & mnt->mnt_fsnotify_mask)
fsnotify_recalc_vfsmount_mask(mnt);
return 0;
}
static int fanotify_remove_inode_mark(struct fsnotify_group *group,
struct inode *inode, __u32 mask)
{
struct fsnotify_mark *fsn_mark = NULL;
__u32 removed;
fsn_mark = fsnotify_find_inode_mark(group, inode);
if (!fsn_mark)
return -ENOENT;
removed = fanotify_mark_remove_from_mask(fsn_mark, mask);
/* matches the fsnotify_find_inode_mark() */
fsnotify_put_mark(fsn_mark);
if (removed & group->mask)
fsnotify_recalc_group_mask(group);
if (removed & inode->i_fsnotify_mask)
fsnotify_recalc_inode_mask(inode);
return 0;
}
static __u32 fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark, __u32 mask)
{
__u32 oldmask;
spin_lock(&fsn_mark->lock);
oldmask = fsn_mark->mask;
fsn_mark->mask = oldmask | mask;
spin_unlock(&fsn_mark->lock);
return mask & ~oldmask;
}
static int fanotify_add_vfsmount_mark(struct fsnotify_group *group,
struct vfsmount *mnt, __u32 mask)
{
struct fsnotify_mark *fsn_mark;
__u32 added;
fsn_mark = fsnotify_find_vfsmount_mark(group, mnt);
if (!fsn_mark) {
int ret;
fsn_mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
if (!fsn_mark)
return -ENOMEM;
fsnotify_init_mark(fsn_mark, fanotify_free_mark);
ret = fsnotify_add_mark(fsn_mark, group, NULL, mnt, 0);
if (ret) {
fanotify_free_mark(fsn_mark);
return ret;
}
}
added = fanotify_mark_add_to_mask(fsn_mark, mask);
fsnotify_put_mark(fsn_mark);
if (added) {
if (added & ~group->mask)
fsnotify_recalc_group_mask(group);
if (added & ~mnt->mnt_fsnotify_mask)
fsnotify_recalc_vfsmount_mask(mnt);
}
return 0;
}
static int fanotify_add_inode_mark(struct fsnotify_group *group,
struct inode *inode, __u32 mask)
{
struct fsnotify_mark *fsn_mark;
__u32 added;
pr_debug("%s: group=%p inode=%p\n", __func__, group, inode);
fsn_mark = fsnotify_find_inode_mark(group, inode);
if (!fsn_mark) {
int ret;
fsn_mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
if (!fsn_mark)
return -ENOMEM;
fsnotify_init_mark(fsn_mark, fanotify_free_mark);
ret = fsnotify_add_mark(fsn_mark, group, inode, NULL, 0);
if (ret) {
fanotify_free_mark(fsn_mark);
return ret;
}
}
added = fanotify_mark_add_to_mask(fsn_mark, mask);
fsnotify_put_mark(fsn_mark);
if (added) {
if (added & ~group->mask)
fsnotify_recalc_group_mask(group);
if (added & ~inode->i_fsnotify_mask)
fsnotify_recalc_inode_mask(inode);
}
return 0;
}
/* fanotify syscalls */
SYSCALL_DEFINE3(fanotify_init, unsigned int, flags, unsigned int, event_f_flags,
unsigned int, priority)
{
struct fsnotify_group *group;
int f_flags, fd;
pr_debug("%s: flags=%d event_f_flags=%d priority=%d\n",
__func__, flags, event_f_flags, priority);
if (event_f_flags)
return -EINVAL;
if (priority)
return -EINVAL;
if (!capable(CAP_SYS_ADMIN))
return -EACCES;
if (flags & ~FAN_ALL_INIT_FLAGS)
return -EINVAL;
f_flags = (O_RDONLY | FMODE_NONOTIFY);
if (flags & FAN_CLOEXEC)
f_flags |= O_CLOEXEC;
if (flags & FAN_NONBLOCK)
f_flags |= O_NONBLOCK;
/* fsnotify_alloc_group takes a ref. Dropped in fanotify_release */
group = fsnotify_alloc_group(&fanotify_fsnotify_ops);
if (IS_ERR(group))
return PTR_ERR(group);
fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);
if (fd < 0)
goto out_put_group;
return fd;
out_put_group:
fsnotify_put_group(group);
return fd;
}
SYSCALL_DEFINE(fanotify_mark)(int fanotify_fd, unsigned int flags,
__u64 mask, int dfd,
const char __user * pathname)
{
struct inode *inode = NULL;
struct vfsmount *mnt = NULL;
struct fsnotify_group *group;
struct file *filp;
struct path path;
int ret, fput_needed;
pr_debug("%s: fanotify_fd=%d flags=%x dfd=%d pathname=%p mask=%llx\n",
__func__, fanotify_fd, flags, dfd, pathname, mask);
/* we only use the lower 32 bits as of right now. */
if (mask & ((__u64)0xffffffff << 32))
return -EINVAL;
if (flags & ~FAN_ALL_MARK_FLAGS)
return -EINVAL;
switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE)) {
case FAN_MARK_ADD:
case FAN_MARK_REMOVE:
break;
default:
return -EINVAL;
}
if (mask & ~(FAN_ALL_EVENTS | FAN_EVENT_ON_CHILD))
return -EINVAL;
filp = fget_light(fanotify_fd, &fput_needed);
if (unlikely(!filp))
return -EBADF;
/* verify that this is indeed an fanotify instance */
ret = -EINVAL;
if (unlikely(filp->f_op != &fanotify_fops))
goto fput_and_out;
ret = fanotify_find_path(dfd, pathname, &path, flags);
if (ret)
goto fput_and_out;
/* inode held in place by reference to path; group by fget on fd */
if (!(flags & FAN_MARK_MOUNT))
inode = path.dentry->d_inode;
else
mnt = path.mnt;
group = filp->private_data;
/* create/update an inode mark */
switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE)) {
case FAN_MARK_ADD:
if (flags & FAN_MARK_MOUNT)
ret = fanotify_add_vfsmount_mark(group, mnt, mask);
else
ret = fanotify_add_inode_mark(group, inode, mask);
break;
case FAN_MARK_REMOVE:
if (flags & FAN_MARK_MOUNT)
ret = fanotify_remove_vfsmount_mark(group, mnt, mask);
else
ret = fanotify_remove_inode_mark(group, inode, mask);
break;
default:
ret = -EINVAL;
}
path_put(&path);
fput_and_out:
fput_light(filp, fput_needed);
return ret;
}
#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
asmlinkage long SyS_fanotify_mark(long fanotify_fd, long flags, __u64 mask,
long dfd, long pathname)
{
return SYSC_fanotify_mark((int) fanotify_fd, (unsigned int) flags,
mask, (int) dfd,
(const char __user *) pathname);
}
SYSCALL_ALIAS(sys_fanotify_mark, SyS_fanotify_mark);
#endif
/*
* fanotify_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 fanotify_user_setup(void)
{
fanotify_mark_cache = KMEM_CACHE(fsnotify_mark, SLAB_PANIC);
return 0;
}
device_initcall(fanotify_user_setup);
|