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linux/sound/drivers
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Takashi Iwai 932dc20e75 ALSA: aloop: Fix racy hw constraints adjustment 
commit 898dfe4687 upstream.

The aloop driver tries to update the hw constraints of the connected
target on the cable of the opened PCM substream.  This is done by
adding the extra hw constraints rules referring to the substream
runtime->hw fields, while the other substream may update the runtime
hw of another side on the fly.

This is, however, racy and may result in the inconsistent values when
both PCM streams perform the prepare concurrently.  One of the reason
is that it overwrites the other's runtime->hw field; which is not only
racy but also broken when it's called before the open of another side
finishes.  And, since the reference to runtime->hw isn't protected,
the concurrent write may give the partial value update and become
inconsistent.

This patch is an attempt to fix and clean up:
- The prepare doesn't change the runtime->hw of other side any longer,
  but only update the cable->hw that is referred commonly.
- The extra rules refer to the loopback_pcm object instead of the
  runtime->hw.  The actual hw is deduced from cable->hw.
- The extra rules take the cable_lock to protect against the race.

Fixes: b1c73fc8e6 ("ALSA: snd-aloop: Fix hw_params restrictions and checking")
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
History 2018-03-03 15:52:14 +00:00
..
mpu401 ALSA: drivers: Convert to snd_card_new() with a device pointer 2014-02-12 10:58:20 +01:00
opl3 ALSA: Drop unused name argument in snd_register_oss_device() 2014-02-12 10:58:19 +01:00
opl4 ALSA: opl4: use list_move_tail instead of list_del/list_add_tail 2012-09-05 09:14:45 +02:00
pcsp ALSA: drivers: Convert to snd_card_new() with a device pointer 2014-02-12 10:58:20 +01:00
vx ALSA: vx_core: off by one in vx_read_status() 2013-06-21 14:32:06 +02:00
aloop.c ALSA: aloop: Fix racy hw constraints adjustment 2018-03-03 15:52:14 +00:00
dummy.c ALSA: dummy: Fix a use-after-free at closing 2016-08-22 22:38:20 +01:00
Kconfig ALSA: sound kconfig typo 2013-04-24 14:02:36 +02:00
Makefile ALSA: introduce the snd-aloop module for the PCM loopback 2010-08-09 14:21:11 +02:00
ml403-ac97cr.c ALSA: drivers: Convert to snd_card_new() with a device pointer 2014-02-12 10:58:20 +01:00
mtpav.c ALSA: drivers: Convert to snd_card_new() with a device pointer 2014-02-12 10:58:20 +01:00
mts64.c ALSA: drivers: Convert to snd_card_new() with a device pointer 2014-02-12 10:58:20 +01:00
pcm-indirect2.c Fix common misspellings 2011-03-31 11:26:23 -03:00
pcm-indirect2.h [ALSA] Xilinx ML403 AC97 Controller Reference device driver 2008-01-31 17:29:15 +01:00
portman2x4.c ALSA: drivers: Convert to snd_card_new() with a device pointer 2014-02-12 10:58:20 +01:00
serial-u16550.c ALSA: drivers: Convert to snd_card_new() with a device pointer 2014-02-12 10:58:20 +01:00
virmidi.c ALSA: drivers: Convert to snd_card_new() with a device pointer 2014-02-12 10:58:20 +01:00