fanotify_user.c

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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/slab.h>
#include <linux/types.h>
#include <linux/uaccess.h>

#include <asm/ioctls.h>

#include "../../mount.h"

#define FANOTIFY_DEFAULT_MAX_EVENTS 16384
#define FANOTIFY_DEFAULT_MAX_MARKS  8192
#define FANOTIFY_DEFAULT_MAX_LISTENERS  128

extern const struct fsnotify_ops fanotify_fsnotify_ops;

static struct kmem_cache *fanotify_mark_cache __read_mostly;
static struct kmem_cache *fanotify_response_event_cache __read_mostly;

struct fanotify_response_event {
    struct list_head list;
    __s32 fd;
    struct fsnotify_event *event;
};

/*
 * 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,
            struct file **file)
{
    int client_fd;
    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.
     */
    /* 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 (event->path.dentry && event->path.mnt)
        new_file = dentry_open(&event->path,
                       group->fanotify_data.f_flags | 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 {
        *file = new_file;
    }

    return client_fd;
}

static int fill_event_metadata(struct fsnotify_group *group,
                   struct fanotify_event_metadata *metadata,
                   struct fsnotify_event *event,
                   struct file **file)
{
    int ret = 0;

    pr_debug("%s: group=%p metadata=%p event=%p\n", __func__,
         group, metadata, event);

    *file = NULL;
    metadata->event_len = FAN_EVENT_METADATA_LEN;
    metadata->metadata_len = FAN_EVENT_METADATA_LEN;
    metadata->vers = FANOTIFY_METADATA_VERSION;
    metadata->mask = event->mask & FAN_ALL_OUTGOING_EVENTS;
    metadata->pid = pid_vnr(event->tgid);
    if (unlikely(event->mask & FAN_Q_OVERFLOW))
        metadata->fd = FAN_NOFD;
    else {
        metadata->fd = create_fd(group, event, file);
        if (metadata->fd < 0)
            ret = metadata->fd;
    }

    return ret;
}

#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
static struct fanotify_response_event *dequeue_re(struct fsnotify_group *group,
                          __s32 fd)
{
    struct fanotify_response_event *re, *return_re = NULL;

    mutex_lock(&group->fanotify_data.access_mutex);
    list_for_each_entry(re, &group->fanotify_data.access_list, list) {
        if (re->fd != fd)
            continue;

        list_del_init(&re->list);
        return_re = re;
        break;
    }
    mutex_unlock(&group->fanotify_data.access_mutex);

    pr_debug("%s: found return_re=%p\n", __func__, return_re);

    return return_re;
}

static int process_access_response(struct fsnotify_group *group,
                   struct fanotify_response *response_struct)
{
    struct fanotify_response_event *re;
    __s32 fd = response_struct->fd;
    __u32 response = response_struct->response;

    pr_debug("%s: group=%p fd=%d response=%d\n", __func__, group,
         fd, response);
    /*
     * make sure the response is valid, if invalid we do nothing and either
     * userspace can send a valid response or we will clean it up after the
     * timeout
     */
    switch (response) {
    case FAN_ALLOW:
    case FAN_DENY:
        break;
    default:
        return -EINVAL;
    }

    if (fd < 0)
        return -EINVAL;

    re = dequeue_re(group, fd);
    if (!re)
        return -ENOENT;

    re->event->response = response;

    wake_up(&group->fanotify_data.access_waitq);

    kmem_cache_free(fanotify_response_event_cache, re);

    return 0;
}

static int prepare_for_access_response(struct fsnotify_group *group,
                       struct fsnotify_event *event,
                       __s32 fd)
{
    struct fanotify_response_event *re;

    if (!(event->mask & FAN_ALL_PERM_EVENTS))
        return 0;

    re = kmem_cache_alloc(fanotify_response_event_cache, GFP_KERNEL);
    if (!re)
        return -ENOMEM;

    re->event = event;
    re->fd = fd;

    mutex_lock(&group->fanotify_data.access_mutex);

    if (atomic_read(&group->fanotify_data.bypass_perm)) {
        mutex_unlock(&group->fanotify_data.access_mutex);
        kmem_cache_free(fanotify_response_event_cache, re);
        event->response = FAN_ALLOW;
        return 0;
    }
        
    list_add_tail(&re->list, &group->fanotify_data.access_list);
    mutex_unlock(&group->fanotify_data.access_mutex);

    return 0;
}

#else
static int prepare_for_access_response(struct fsnotify_group *group,
                       struct fsnotify_event *event,
                       __s32 fd)
{
    return 0;
}

#endif

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;
    struct file *f;
    int fd, ret;

    pr_debug("%s: group=%p event=%p\n", __func__, group, event);

    ret = fill_event_metadata(group, &fanotify_event_metadata, event, &f);
    if (ret < 0)
        goto out;

    fd = fanotify_event_metadata.fd;
    ret = -EFAULT;
    if (copy_to_user(buf, &fanotify_event_metadata,
             fanotify_event_metadata.event_len))
        goto out_close_fd;

    ret = prepare_for_access_response(group, event, fd);
    if (ret)
        goto out_close_fd;

    if (fd != FAN_NOFD)
        fd_install(fd, f);
    return fanotify_event_metadata.event_len;

out_close_fd:
    if (fd != FAN_NOFD) {
        put_unused_fd(fd);
        fput(f);
    }
out:
#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
    if (event->mask & FAN_ALL_PERM_EVENTS) {
        event->response = FAN_DENY;
        wake_up(&group->fanotify_data.access_waitq);
    }
#endif
    return ret;
}

/* 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 = -ERESTARTSYS;
        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 ssize_t fanotify_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
{
#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
    struct fanotify_response response = { .fd = -1, .response = -1 };
    struct fsnotify_group *group;
    int ret;

    group = file->private_data;

    if (count > sizeof(response))
        count = sizeof(response);

    pr_debug("%s: group=%p count=%zu\n", __func__, group, count);

    if (copy_from_user(&response, buf, count))
        return -EFAULT;

    ret = process_access_response(group, &response);
    if (ret < 0)
        count = ret;

    return count;
#else
    return -EINVAL;
#endif
}

static int fanotify_release(struct inode *ignored, struct file *file)
{
    struct fsnotify_group *group = file->private_data;

#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
    struct fanotify_response_event *re, *lre;

    mutex_lock(&group->fanotify_data.access_mutex);

    atomic_inc(&group->fanotify_data.bypass_perm);

    list_for_each_entry_safe(re, lre, &group->fanotify_data.access_list, list) {
        pr_debug("%s: found group=%p re=%p event=%p\n", __func__, group,
             re, re->event);

        list_del_init(&re->list);
        re->event->response = FAN_ALLOW;

        kmem_cache_free(fanotify_response_event_cache, re);
    }
    mutex_unlock(&group->fanotify_data.access_mutex);

    wake_up(&group->fanotify_data.access_waitq);
#endif
    /* 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,
    .write      = fanotify_write,
    .fasync     = NULL,
    .release    = fanotify_release,
    .unlocked_ioctl = fanotify_ioctl,
    .compat_ioctl   = fanotify_ioctl,
    .llseek     = noop_llseek,
};

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 fd f = fdget(dfd);

        ret = -EBADF;
        if (!f.file)
            goto out;

        ret = -ENOTDIR;
        if ((flags & FAN_MARK_ONLYDIR) &&
            !(S_ISDIR(f.file->f_path.dentry->d_inode->i_mode))) {
            fdput(f);
            goto out;
        }

        *path = f.file->f_path;
        path_get(path);
        fdput(f);
    } 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,
                        unsigned int flags)
{
    __u32 oldmask;

    spin_lock(&fsn_mark->lock);
    if (!(flags & FAN_MARK_IGNORED_MASK)) {
        oldmask = fsn_mark->mask;
        fsnotify_set_mark_mask_locked(fsn_mark, (oldmask & ~mask));
    } else {
        oldmask = fsn_mark->ignored_mask;
        fsnotify_set_mark_ignored_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,
                     unsigned int flags)
{
    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, flags);
    fsnotify_put_mark(fsn_mark);
    if (removed & real_mount(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,
                      unsigned int flags)
{
    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, flags);
    /* matches the fsnotify_find_inode_mark() */
    fsnotify_put_mark(fsn_mark);
    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,
                       unsigned int flags)
{
    __u32 oldmask = -1;

    spin_lock(&fsn_mark->lock);
    if (!(flags & FAN_MARK_IGNORED_MASK)) {
        oldmask = fsn_mark->mask;
        fsnotify_set_mark_mask_locked(fsn_mark, (oldmask | mask));
    } else {
        __u32 tmask = fsn_mark->ignored_mask | mask;
        fsnotify_set_mark_ignored_mask_locked(fsn_mark, tmask);
        if (flags & FAN_MARK_IGNORED_SURV_MODIFY)
            fsn_mark->flags |= FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY;
    }

    if (!(flags & FAN_MARK_ONDIR)) {
        __u32 tmask = fsn_mark->ignored_mask | FAN_ONDIR;
        fsnotify_set_mark_ignored_mask_locked(fsn_mark, tmask);
    }

    spin_unlock(&fsn_mark->lock);

    return mask & ~oldmask;
}

static int fanotify_add_vfsmount_mark(struct fsnotify_group *group,
                      struct vfsmount *mnt, __u32 mask,
                      unsigned int flags)
{
    struct fsnotify_mark *fsn_mark;
    __u32 added;
    int ret = 0;

    fsn_mark = fsnotify_find_vfsmount_mark(group, mnt);
    if (!fsn_mark) {
        if (atomic_read(&group->num_marks) > group->fanotify_data.max_marks)
            return -ENOSPC;

        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)
            goto err;
    }
    added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);

    if (added & ~real_mount(mnt)->mnt_fsnotify_mask)
        fsnotify_recalc_vfsmount_mask(mnt);
err:
    fsnotify_put_mark(fsn_mark);
    return ret;
}

static int fanotify_add_inode_mark(struct fsnotify_group *group,
                   struct inode *inode, __u32 mask,
                   unsigned int flags)
{
    struct fsnotify_mark *fsn_mark;
    __u32 added;
    int ret = 0;

    pr_debug("%s: group=%p inode=%p\n", __func__, group, inode);

    /*
     * If some other task has this inode open for write we should not add
     * an ignored mark, unless that ignored mark is supposed to survive
     * modification changes anyway.
     */
    if ((flags & FAN_MARK_IGNORED_MASK) &&
        !(flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
        (atomic_read(&inode->i_writecount) > 0))
        return 0;

    fsn_mark = fsnotify_find_inode_mark(group, inode);
    if (!fsn_mark) {
        if (atomic_read(&group->num_marks) > group->fanotify_data.max_marks)
            return -ENOSPC;

        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)
            goto err;
    }
    added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);

    if (added & ~inode->i_fsnotify_mask)
        fsnotify_recalc_inode_mask(inode);
err:
    fsnotify_put_mark(fsn_mark);
    return ret;
}

/* fanotify syscalls */
SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
{
    struct fsnotify_group *group;
    int f_flags, fd;
    struct user_struct *user;

    pr_debug("%s: flags=%d event_f_flags=%d\n",
        __func__, flags, event_f_flags);

    if (!capable(CAP_SYS_ADMIN))
        return -EPERM;

    if (flags & ~FAN_ALL_INIT_FLAGS)
        return -EINVAL;

    user = get_current_user();
    if (atomic_read(&user->fanotify_listeners) > FANOTIFY_DEFAULT_MAX_LISTENERS) {
        free_uid(user);
        return -EMFILE;
    }

    f_flags = O_RDWR | 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)) {
        free_uid(user);
        return PTR_ERR(group);
    }

    group->fanotify_data.user = user;
    atomic_inc(&user->fanotify_listeners);

    group->fanotify_data.f_flags = event_f_flags;
#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
    mutex_init(&group->fanotify_data.access_mutex);
    init_waitqueue_head(&group->fanotify_data.access_waitq);
    INIT_LIST_HEAD(&group->fanotify_data.access_list);
    atomic_set(&group->fanotify_data.bypass_perm, 0);
#endif
    switch (flags & FAN_ALL_CLASS_BITS) {
    case FAN_CLASS_NOTIF:
        group->priority = FS_PRIO_0;
        break;
    case FAN_CLASS_CONTENT:
        group->priority = FS_PRIO_1;
        break;
    case FAN_CLASS_PRE_CONTENT:
        group->priority = FS_PRIO_2;
        break;
    default:
        fd = -EINVAL;
        goto out_put_group;
    }

    if (flags & FAN_UNLIMITED_QUEUE) {
        fd = -EPERM;
        if (!capable(CAP_SYS_ADMIN))
            goto out_put_group;
        group->max_events = UINT_MAX;
    } else {
        group->max_events = FANOTIFY_DEFAULT_MAX_EVENTS;
    }

    if (flags & FAN_UNLIMITED_MARKS) {
        fd = -EPERM;
        if (!capable(CAP_SYS_ADMIN))
            goto out_put_group;
        group->fanotify_data.max_marks = UINT_MAX;
    } else {
        group->fanotify_data.max_marks = FANOTIFY_DEFAULT_MAX_MARKS;
    }

    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 fd f;
    struct path path;
    int ret;

    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 | FAN_MARK_FLUSH)) {
    case FAN_MARK_ADD:      /* fallthrough */
    case FAN_MARK_REMOVE:
        if (!mask)
            return -EINVAL;
    case FAN_MARK_FLUSH:
        break;
    default:
        return -EINVAL;
    }

    if (mask & FAN_ONDIR) {
        flags |= FAN_MARK_ONDIR;
        mask &= ~FAN_ONDIR;
    }

#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
    if (mask & ~(FAN_ALL_EVENTS | FAN_ALL_PERM_EVENTS | FAN_EVENT_ON_CHILD))
#else
    if (mask & ~(FAN_ALL_EVENTS | FAN_EVENT_ON_CHILD))
#endif
        return -EINVAL;

    f = fdget(fanotify_fd);
    if (unlikely(!f.file))
        return -EBADF;

    /* verify that this is indeed an fanotify instance */
    ret = -EINVAL;
    if (unlikely(f.file->f_op != &fanotify_fops))
        goto fput_and_out;
    group = f.file->private_data;

    /*
     * group->priority == FS_PRIO_0 == FAN_CLASS_NOTIF.  These are not
     * allowed to set permissions events.
     */
    ret = -EINVAL;
    if (mask & FAN_ALL_PERM_EVENTS &&
        group->priority == FS_PRIO_0)
        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;

    /* create/update an inode mark */
    switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE | FAN_MARK_FLUSH)) {
    case FAN_MARK_ADD:
        if (flags & FAN_MARK_MOUNT)
            ret = fanotify_add_vfsmount_mark(group, mnt, mask, flags);
        else
            ret = fanotify_add_inode_mark(group, inode, mask, flags);
        break;
    case FAN_MARK_REMOVE:
        if (flags & FAN_MARK_MOUNT)
            ret = fanotify_remove_vfsmount_mark(group, mnt, mask, flags);
        else
            ret = fanotify_remove_inode_mark(group, inode, mask, flags);
        break;
    case FAN_MARK_FLUSH:
        if (flags & FAN_MARK_MOUNT)
            fsnotify_clear_vfsmount_marks_by_group(group);
        else
            fsnotify_clear_inode_marks_by_group(group);
        break;
    default:
        ret = -EINVAL;
    }

    path_put(&path);
fput_and_out:
    fdput(f);
    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 cannot 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);
    fanotify_response_event_cache = KMEM_CACHE(fanotify_response_event,
                           SLAB_PANIC);

    return 0;
}
device_initcall(fanotify_user_setup);