// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * 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 rewritten to make use of the fsnotify infrastructure
 */

#include <linux/dcache.h> /* d_unlinked */
#include <linux/fs.h> /* struct inode */
#include <linux/fsnotify_backend.h>
#include <linux/inotify.h>
#include <linux/path.h> /* struct path */
#include <linux/slab.h> /* kmem_* */
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/sched/user.h>
#include <linux/sched/mm.h>

#include "inotify.h"

/*
 * Check if 2 events contain the same information.
 */
static bool event_compare(struct fsnotify_event *old_fsn,
                          struct fsnotify_event *new_fsn)
{
        struct inotify_event_info *old, *new;

        old = INOTIFY_E(old_fsn);
        new = INOTIFY_E(new_fsn);
        if (old->mask & FS_IN_IGNORED)
                return false;
        if ((old->mask == new->mask) &&
            (old->wd == new->wd) &&
            (old->name_len == new->name_len) &&
            (!old->name_len || !strcmp(old->name, new->name)))
                return true;
        return false;
}

static int inotify_merge(struct fsnotify_group *group,
                         struct fsnotify_event *event)
{
        struct list_head *list = &group->notification_list;
        struct fsnotify_event *last_event;

        last_event = list_entry(list->prev, struct fsnotify_event, list);
        return event_compare(last_event, event);
}

int inotify_handle_inode_event(struct fsnotify_mark *inode_mark, u32 mask,
                               struct inode *inode, struct inode *dir,
                               const struct qstr *name, u32 cookie)
{
        struct inotify_inode_mark *i_mark;
        struct inotify_event_info *event;
        struct fsnotify_event *fsn_event;
        struct fsnotify_group *group = inode_mark->group;
        int ret;
        int len = 0, wd;
        int alloc_len = sizeof(struct inotify_event_info);
        struct mem_cgroup *old_memcg;

        if (name) {
                len = name->len;
                alloc_len += len + 1;
        }

        pr_debug("%s: group=%p mark=%p mask=%x\n", __func__, group, inode_mark,
                 mask);

        i_mark = container_of(inode_mark, struct inotify_inode_mark,
                              fsn_mark);

        /*
         * We can be racing with mark being detached. Don't report event with
         * invalid wd.
         */
        wd = READ_ONCE(i_mark->wd);
        if (wd == -1)
                return 0;
        /*
         * Whoever is interested in the event, pays for the allocation. Do not
         * trigger OOM killer in the target monitoring memcg as it may have
         * security repercussion.
         */
        old_memcg = set_active_memcg(group->memcg);
        event = kmalloc(alloc_len, GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL);
        set_active_memcg(old_memcg);

        if (unlikely(!event)) {
                /*
                 * Treat lost event due to ENOMEM the same way as queue
                 * overflow to let userspace know event was lost.
                 */
                fsnotify_queue_overflow(group);
                return -ENOMEM;
        }

        /*
         * We now report FS_ISDIR flag with MOVE_SELF and DELETE_SELF events
         * for fanotify. inotify never reported IN_ISDIR with those events.
         * It looks like an oversight, but to avoid the risk of breaking
         * existing inotify programs, mask the flag out from those events.
         */
        if (mask & (IN_MOVE_SELF | IN_DELETE_SELF))
                mask &= ~IN_ISDIR;

        fsn_event = &event->fse;
        fsnotify_init_event(fsn_event);
        event->mask = mask;
        event->wd = wd;
        event->sync_cookie = cookie;
        event->name_len = len;
        if (len)
                strscpy(event->name, name->name, event->name_len + 1);

        ret = fsnotify_add_event(group, fsn_event, inotify_merge);
        if (ret) {
                /* Our event wasn't used in the end. Free it. */
                fsnotify_destroy_event(group, fsn_event);
        }

        if (inode_mark->flags & FSNOTIFY_MARK_FLAG_IN_ONESHOT)
                fsnotify_destroy_mark(inode_mark, group);

        return 0;
}

static void inotify_freeing_mark(struct fsnotify_mark *fsn_mark, struct fsnotify_group *group)
{
        inotify_ignored_and_remove_idr(fsn_mark, group);
}

/*
 * This is NEVER supposed to be called.  Inotify marks should either have been
 * removed from the idr when the watch was removed or in the
 * fsnotify_destroy_mark_by_group() call when the inotify instance was being
 * torn down.  This is only called if the idr is about to be freed but there
 * are still marks in it.
 */
static int idr_callback(int id, void *p, void *data)
{
        struct fsnotify_mark *fsn_mark;
        struct inotify_inode_mark *i_mark;
        static bool warned = false;

        if (warned)
                return 0;

        warned = true;
        fsn_mark = p;
        i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);

        WARN(1, "inotify closing but id=%d for fsn_mark=%p in group=%p still in "
                "idr.  Probably leaking memory\n", id, p, data);

        /*
         * I'm taking the liberty of assuming that the mark in question is a
         * valid address and I'm dereferencing it.  This might help to figure
         * out why we got here and the panic is no worse than the original
         * BUG() that was here.
         */
        if (fsn_mark)
                printk(KERN_WARNING "fsn_mark->group=%p wd=%d\n",
                        fsn_mark->group, i_mark->wd);
        return 0;
}

static void inotify_free_group_priv(struct fsnotify_group *group)
{
        /* ideally the idr is empty and we won't hit the BUG in the callback */
        idr_for_each(&group->inotify_data.idr, idr_callback, group);
        idr_destroy(&group->inotify_data.idr);
        if (group->inotify_data.ucounts)
                dec_inotify_instances(group->inotify_data.ucounts);
}

static void inotify_free_event(struct fsnotify_group *group,
                               struct fsnotify_event *fsn_event)
{
        kfree(INOTIFY_E(fsn_event));
}

/* ding dong the mark is dead */
static void inotify_free_mark(struct fsnotify_mark *fsn_mark)
{
        struct inotify_inode_mark *i_mark;

        i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);

        kmem_cache_free(inotify_inode_mark_cachep, i_mark);
}

const struct fsnotify_ops inotify_fsnotify_ops = {
        .handle_inode_event = inotify_handle_inode_event,
        .free_group_priv = inotify_free_group_priv,
        .free_event = inotify_free_event,
        .freeing_mark = inotify_freeing_mark,
        .free_mark = inotify_free_mark,
};