text: // 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 rewriten 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;
  	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);
  
  	/*
  	 * 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 = i_mark->wd;
  	event->sync_cookie = cookie;
  	event->name_len = len;
  	if (len)
  		strcpy(event->name, name->name);
  
  	ret = fsnotify_add_event(group, fsn_event, inotify_merge, NULL);
  	if (ret) {
  		/* Our event wasn't used in the end. Free it. */
  		fsnotify_destroy_event(group, fsn_event);
  	}
  
  	if (inode_mark->mask & 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_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,
  };
  