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12703dbfeb
Implement a function that can be called when a group is being shutdown
to stop queueing new events to the group. Fanotify will use this.
Fixes: 5838d4442b ("fanotify: fix double free of pending permission events")
Link: http://lkml.kernel.org/r/1473797711-14111-2-git-send-email-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
147 lines
4.0 KiB
C
147 lines
4.0 KiB
C
/*
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* Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; see the file COPYING. If not, write to
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* the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <linux/list.h>
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#include <linux/mutex.h>
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#include <linux/slab.h>
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#include <linux/srcu.h>
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#include <linux/rculist.h>
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#include <linux/wait.h>
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#include <linux/fsnotify_backend.h>
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#include "fsnotify.h"
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#include <linux/atomic.h>
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/*
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* Final freeing of a group
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*/
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static void fsnotify_final_destroy_group(struct fsnotify_group *group)
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{
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if (group->ops->free_group_priv)
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group->ops->free_group_priv(group);
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kfree(group);
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}
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/*
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* Stop queueing new events for this group. Once this function returns
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* fsnotify_add_event() will not add any new events to the group's queue.
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*/
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void fsnotify_group_stop_queueing(struct fsnotify_group *group)
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{
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mutex_lock(&group->notification_mutex);
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group->shutdown = true;
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mutex_unlock(&group->notification_mutex);
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}
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/*
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* Trying to get rid of a group. Remove all marks, flush all events and release
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* the group reference.
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* Note that another thread calling fsnotify_clear_marks_by_group() may still
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* hold a ref to the group.
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*/
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void fsnotify_destroy_group(struct fsnotify_group *group)
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{
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/*
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* Stop queueing new events. The code below is careful enough to not
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* require this but fanotify needs to stop queuing events even before
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* fsnotify_destroy_group() is called and this makes the other callers
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* of fsnotify_destroy_group() to see the same behavior.
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*/
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fsnotify_group_stop_queueing(group);
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/* clear all inode marks for this group, attach them to destroy_list */
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fsnotify_detach_group_marks(group);
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/*
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* Wait for fsnotify_mark_srcu period to end and free all marks in
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* destroy_list
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*/
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fsnotify_mark_destroy_list();
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/*
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* Since we have waited for fsnotify_mark_srcu in
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* fsnotify_mark_destroy_list() there can be no outstanding event
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* notification against this group. So clearing the notification queue
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* of all events is reliable now.
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*/
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fsnotify_flush_notify(group);
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/*
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* Destroy overflow event (we cannot use fsnotify_destroy_event() as
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* that deliberately ignores overflow events.
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*/
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if (group->overflow_event)
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group->ops->free_event(group->overflow_event);
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fsnotify_put_group(group);
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}
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/*
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* Get reference to a group.
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*/
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void fsnotify_get_group(struct fsnotify_group *group)
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{
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atomic_inc(&group->refcnt);
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}
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/*
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* Drop a reference to a group. Free it if it's through.
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*/
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void fsnotify_put_group(struct fsnotify_group *group)
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{
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if (atomic_dec_and_test(&group->refcnt))
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fsnotify_final_destroy_group(group);
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}
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/*
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* Create a new fsnotify_group and hold a reference for the group returned.
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*/
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struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
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{
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struct fsnotify_group *group;
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group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL);
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if (!group)
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return ERR_PTR(-ENOMEM);
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/* set to 0 when there a no external references to this group */
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atomic_set(&group->refcnt, 1);
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atomic_set(&group->num_marks, 0);
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mutex_init(&group->notification_mutex);
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INIT_LIST_HEAD(&group->notification_list);
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init_waitqueue_head(&group->notification_waitq);
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group->max_events = UINT_MAX;
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mutex_init(&group->mark_mutex);
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INIT_LIST_HEAD(&group->marks_list);
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group->ops = ops;
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return group;
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}
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int fsnotify_fasync(int fd, struct file *file, int on)
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{
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struct fsnotify_group *group = file->private_data;
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return fasync_helper(fd, file, on, &group->fsn_fa) >= 0 ? 0 : -EIO;
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}
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