OpenCloudOS-Kernel/sound/core/seq/seq_queue.h

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/*
* ALSA sequencer Queue handling
* Copyright (c) 1998-1999 by Frank van de Pol <fvdpol@coil.demon.nl>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
#ifndef __SND_SEQ_QUEUE_H
#define __SND_SEQ_QUEUE_H
#include "seq_memory.h"
#include "seq_prioq.h"
#include "seq_timer.h"
#include "seq_lock.h"
#include <linux/interrupt.h>
#include <linux/list.h>
#include <linux/bitops.h>
#define SEQ_QUEUE_NO_OWNER (-1)
struct snd_seq_queue {
int queue; /* queue number */
char name[64]; /* name of this queue */
struct snd_seq_prioq *tickq; /* midi tick event queue */
struct snd_seq_prioq *timeq; /* real-time event queue */
struct snd_seq_timer *timer; /* time keeper for this queue */
int owner; /* client that 'owns' the timer */
unsigned int locked:1, /* timer is only accesibble by owner if set */
klocked:1, /* kernel lock (after START) */
check_again:1,
check_blocked:1;
unsigned int flags; /* status flags */
unsigned int info_flags; /* info for sync */
spinlock_t owner_lock;
spinlock_t check_lock;
/* clients which uses this queue (bitmap) */
DECLARE_BITMAP(clients_bitmap, SNDRV_SEQ_MAX_CLIENTS);
unsigned int clients; /* users of this queue */
struct mutex timer_mutex;
snd_use_lock_t use_lock;
};
/* get the number of current queues */
int snd_seq_queue_get_cur_queues(void);
/* delete queues */
void snd_seq_queues_delete(void);
/* create new queue (constructor) */
ALSA: seq: 2nd attempt at fixing race creating a queue commit 4842e98f26dd80be3623c4714a244ba52ea096a8 ("ALSA: seq: Fix race at creating a queue") attempted to fix a race reported by syzkaller. That fix has been described as follows: " When a sequencer queue is created in snd_seq_queue_alloc(),it adds the new queue element to the public list before referencing it. Thus the queue might be deleted before the call of snd_seq_queue_use(), and it results in the use-after-free error, as spotted by syzkaller. The fix is to reference the queue object at the right time. " Even with that fix in place, syzkaller reported a use-after-free error. It specifically pointed to the last instruction "return q->queue" in snd_seq_queue_alloc(). The pointer q is being used after kfree() has been called on it. It turned out that there is still a small window where a race can happen. The window opens at snd_seq_ioctl_create_queue()->snd_seq_queue_alloc()->queue_list_add() and closes at snd_seq_ioctl_create_queue()->queueptr()->snd_use_lock_use(). Between these two calls, a different thread could delete the queue and possibly re-create a different queue in the same location in queue_list. This change prevents this situation by calling snd_use_lock_use() from snd_seq_queue_alloc() prior to calling queue_list_add(). It is then the caller's responsibility to call snd_use_lock_free(&q->use_lock). Fixes: 4842e98f26dd ("ALSA: seq: Fix race at creating a queue") Reported-by: Dmitry Vyukov <dvyukov@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Daniel Mentz <danielmentz@google.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2017-08-15 05:46:01 +08:00
struct snd_seq_queue *snd_seq_queue_alloc(int client, int locked, unsigned int flags);
/* delete queue (destructor) */
int snd_seq_queue_delete(int client, int queueid);
/* notification that client has left the system */
void snd_seq_queue_client_termination(int client);
/* final stage */
void snd_seq_queue_client_leave(int client);
/* enqueue a event received from one the clients */
int snd_seq_enqueue_event(struct snd_seq_event_cell *cell, int atomic, int hop);
/* Remove events */
void snd_seq_queue_client_leave_cells(int client);
void snd_seq_queue_remove_cells(int client, struct snd_seq_remove_events *info);
/* return pointer to queue structure for specified id */
struct snd_seq_queue *queueptr(int queueid);
/* unlock */
#define queuefree(q) snd_use_lock_free(&(q)->use_lock)
/* return the (first) queue matching with the specified name */
struct snd_seq_queue *snd_seq_queue_find_name(char *name);
/* check single queue and dispatch events */
void snd_seq_check_queue(struct snd_seq_queue *q, int atomic, int hop);
/* access to queue's parameters */
int snd_seq_queue_check_access(int queueid, int client);
int snd_seq_queue_timer_set_tempo(int queueid, int client, struct snd_seq_queue_tempo *info);
int snd_seq_queue_set_owner(int queueid, int client, int locked);
int snd_seq_queue_set_locked(int queueid, int client, int locked);
int snd_seq_queue_timer_open(int queueid);
int snd_seq_queue_timer_close(int queueid);
int snd_seq_queue_use(int queueid, int client, int use);
int snd_seq_queue_is_used(int queueid, int client);
int snd_seq_control_queue(struct snd_seq_event *ev, int atomic, int hop);
#endif