ALSA: pcm: Fix races among concurrent prepare and hw_params/hw_free calls
authorTakashi Iwai <tiwai@suse.de>
Tue, 22 Mar 2022 17:07:19 +0000 (18:07 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Mon, 28 Mar 2022 07:58:43 +0000 (09:58 +0200)
commitcb6a39c5ebd0a125c420c5a10999813daaece019
tree96615de4ea1f807181639afdf7b1a6cc99a0bcdb
parent47711ff10c7e126702cfa725f6d86ef529d15a5f
ALSA: pcm: Fix races among concurrent prepare and hw_params/hw_free calls

commit 3c3201f8c7bb77eb53b08a3ca8d9a4ddc500b4c0 upstream.

Like the previous fixes to hw_params and hw_free ioctl races, we need
to paper over the concurrent prepare ioctl calls against hw_params and
hw_free, too.

This patch implements the locking with the existing
runtime->buffer_mutex for prepare ioctls.  Unlike the previous case
for snd_pcm_hw_hw_params() and snd_pcm_hw_free(), snd_pcm_prepare() is
performed to the linked streams, hence the lock can't be applied
simply on the top.  For tracking the lock in each linked substream, we
modify snd_pcm_action_group() slightly and apply the buffer_mutex for
the case stream_lock=false (formerly there was no lock applied)
there.

Cc: <stable@vger.kernel.org>
Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20220322170720.3529-4-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sound/core/pcm_native.c