linux/include/sound/pcm_oss.h
Takashi Iwai 40cab6e88c ALSA: pcm: Return -EBUSY for OSS ioctls changing busy streams
OSS PCM stream management isn't modal but it allows ioctls issued at
any time for changing the parameters.  In the previous hardening
patch ("ALSA: pcm: Avoid potential races between OSS ioctls and
read/write"), we covered these races and prevent the corruption by
protecting the concurrent accesses via params_lock mutex.  However,
this means that some ioctls that try to change the stream parameter
(e.g. channels or format) would be blocked until the read/write
finishes, and it may take really long.

Basically changing the parameter while reading/writing is an invalid
operation, hence it's even more user-friendly from the API POV if it
returns -EBUSY in such a situation.

This patch adds such checks in the relevant ioctls with the addition
of read/write access refcount.

Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
2018-03-23 22:18:05 +01:00

91 lines
2.7 KiB
C

#ifndef __SOUND_PCM_OSS_H
#define __SOUND_PCM_OSS_H
/*
* Digital Audio (PCM) - OSS compatibility abstract layer
* Copyright (c) by Jaroslav Kysela <perex@perex.cz>
*
*
* 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
*
*/
struct snd_pcm_oss_setup {
char *task_name;
unsigned int disable:1,
direct:1,
block:1,
nonblock:1,
partialfrag:1,
nosilence:1,
buggyptr:1;
unsigned int periods;
unsigned int period_size;
struct snd_pcm_oss_setup *next;
};
struct snd_pcm_oss_runtime {
unsigned params: 1, /* format/parameter change */
prepare: 1, /* need to prepare the operation */
trigger: 1, /* trigger flag */
sync_trigger: 1; /* sync trigger flag */
int rate; /* requested rate */
int format; /* requested OSS format */
unsigned int channels; /* requested channels */
unsigned int fragshift;
unsigned int maxfrags;
unsigned int subdivision; /* requested subdivision */
size_t period_bytes; /* requested period size */
size_t period_frames; /* period frames for poll */
size_t period_ptr; /* actual write pointer to period */
unsigned int periods;
size_t buffer_bytes; /* requested buffer size */
size_t bytes; /* total # bytes processed */
size_t mmap_bytes;
char *buffer; /* vmallocated period */
size_t buffer_used; /* used length from period buffer */
struct mutex params_lock;
atomic_t rw_ref; /* concurrent read/write accesses */
#ifdef CONFIG_SND_PCM_OSS_PLUGINS
struct snd_pcm_plugin *plugin_first;
struct snd_pcm_plugin *plugin_last;
#endif
unsigned int prev_hw_ptr_period;
};
struct snd_pcm_oss_file {
struct snd_pcm_substream *streams[2];
};
struct snd_pcm_oss_substream {
unsigned oss: 1; /* oss mode */
struct snd_pcm_oss_setup setup; /* active setup */
};
struct snd_pcm_oss_stream {
struct snd_pcm_oss_setup *setup_list; /* setup list */
struct mutex setup_mutex;
#ifdef CONFIG_SND_VERBOSE_PROCFS
struct snd_info_entry *proc_entry;
#endif
};
struct snd_pcm_oss {
int reg;
unsigned int reg_mask;
};
#endif /* __SOUND_PCM_OSS_H */