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ALSA: firewire-motu: Protect register DSP event queue positions

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The register DSP event queue is updated under parser->lock, but
snd_motu_register_dsp_message_parser_count_event() reads pull_pos and
push_pos without the lock.
snd_motu_register_dsp_message_parser_copy_event() also reads both queue
positions before taking the lock.

Protect these accesses with parser->lock as well. This keeps the hwdep
poll/read path consistent with the producer side and with the cached
meter/parameter accessors.

Fixes: 634ec0b290 ("ALSA: firewire-motu: notify event for parameter change in register DSP model")
Cc: stable@vger.kernel.org
Signed-off-by: Cássio Gabriel <cassiogabrielcontato@gmail.com>
Reviewed-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20260521-alsa-firewire-motu-event-locking-v1-1-708e1c2b5e56@gmail.com
This commit is contained in:
Cássio Gabriel 2026-05-21 08:01:23 -03:00 committed by Takashi Iwai
parent 2519003dd5
commit 98fb1c1bb1
1 changed files with 7 additions and 4 deletions
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11
sound/firewire/motu/motu-register-dsp-message-parser.c
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@ -386,6 +386,8 @@ unsigned int snd_motu_register_dsp_message_parser_count_event(struct snd_motu *m
{
struct msg_parser *parser = motu->message_parser;
guard(spinlock_irqsave)(&parser->lock);
if (parser->pull_pos > parser->push_pos)
return EVENT_QUEUE_SIZE - parser->pull_pos + parser->push_pos;
else
@ -395,13 +397,14 @@ unsigned int snd_motu_register_dsp_message_parser_count_event(struct snd_motu *m
bool snd_motu_register_dsp_message_parser_copy_event(struct snd_motu *motu, u32 *event)
{
struct msg_parser *parser = motu->message_parser;
unsigned int pos = parser->pull_pos;
if (pos == parser->push_pos)
return false;
unsigned int pos;
guard(spinlock_irqsave)(&parser->lock);
if (parser->pull_pos == parser->push_pos)
return false;
pos = parser->pull_pos;
*event = parser->event_queue[pos];
++pos;