FAILED: patch "[PATCH] ALSA: firewire-motu: Protect register DSP event queue" failed to apply to 6.1-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 98fb1c1bb11e29eb609b7200a25e136e05aa4498
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026060437-throttle-colossal-060d@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 98fb1c1bb11e29eb609b7200a25e136e05aa4498 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A1ssio=20Gabriel?= <cassiogabrielcontato@gmail.com>
Date: Thu, 21 May 2026 08:01:23 -0300
Subject: [PATCH] ALSA: firewire-motu: Protect register DSP event queue
 positions
MIME-Version: 1.0
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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: 634ec0b2906e ("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

diff --git a/sound/firewire/motu/motu-register-dsp-message-parser.c b/sound/firewire/motu/motu-register-dsp-message-parser.c
index a8053e3ef065..4ec23e6880d9 100644
--- a/sound/firewire/motu/motu-register-dsp-message-parser.c
+++ b/sound/firewire/motu/motu-register-dsp-message-parser.c
@@ -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;