linux/fs/notify/fanotify/fanotify_user.c
Eric Paris 90b1e7a578 fsnotify: allow marks to not pin inodes in core
inotify marks must pin inodes in core.  dnotify doesn't technically need to
since they are closed when the directory is closed.  fanotify also need to
pin inodes in core as it works today.  But the next step is to introduce
the concept of 'ignored masks' which is actually a mask of events for an
inode of no interest.  I claim that these should be liberally sent to the
kernel and should not pin the inode in core.  If the inode is brought back
in the listener will get an event it may have thought excluded, but this is
not a serious situation and one any listener should deal with.

This patch lays the ground work for non-pinning inode marks by using lazy
inode pinning.  We do not pin a mark until it has a non-zero mask entry.  If a
listener new sets a mask we never pin the inode.

Signed-off-by: Eric Paris <eparis@redhat.com>
2010-07-28 09:58:59 -04:00

574 lines
14 KiB
C

#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;
fsnotify_set_mark_mask_locked(fsn_mark, (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;
fsnotify_set_mark_mask_locked(fsn_mark, (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);