linux-kernel - [PATCH AUTOSEL 6.6 069/139] ALSA: hdsp: Break infinite MIDI input flush loop

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Message-ID: <20240925121137.1307574-69-sashal@kernel.org>
Date: Wed, 25 Sep 2024 08:08:09 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Takashi Iwai <tiwai@...e.de>,
	Sasha Levin <sashal@...nel.org>,
	perex@...ex.cz,
	tiwai@...e.com,
	linux-sound@...r.kernel.org
Subject: [PATCH AUTOSEL 6.6 069/139] ALSA: hdsp: Break infinite MIDI input flush loop

From: Takashi Iwai <tiwai@...e.de>

[ Upstream commit c01f3815453e2d5f699ccd8c8c1f93a5b8669e59 ]

The current MIDI input flush on HDSP and HDSPM drivers relies on the
hardware reporting the right value.  If the hardware doesn't give the
proper value but returns -1, it may be stuck at an infinite loop.

Add a counter and break if the loop is unexpectedly too long.

Link: https://patch.msgid.link/20240808091513.31380-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 sound/pci/rme9652/hdsp.c  | 6 ++++--
 sound/pci/rme9652/hdspm.c | 6 ++++--
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/sound/pci/rme9652/hdsp.c b/sound/pci/rme9652/hdsp.c
index e7d1b43471a29..713ca262a0e97 100644
--- a/sound/pci/rme9652/hdsp.c
+++ b/sound/pci/rme9652/hdsp.c
@@ -1298,8 +1298,10 @@ static int snd_hdsp_midi_output_possible (struct hdsp *hdsp, int id)
 
 static void snd_hdsp_flush_midi_input (struct hdsp *hdsp, int id)
 {
-	while (snd_hdsp_midi_input_available (hdsp, id))
-		snd_hdsp_midi_read_byte (hdsp, id);
+	int count = 256;
+
+	while (snd_hdsp_midi_input_available(hdsp, id) && --count)
+		snd_hdsp_midi_read_byte(hdsp, id);
 }
 
 static int snd_hdsp_midi_output_write (struct hdsp_midi *hmidi)
diff --git a/sound/pci/rme9652/hdspm.c b/sound/pci/rme9652/hdspm.c
index 267c7848974ae..74215f57f4fc9 100644
--- a/sound/pci/rme9652/hdspm.c
+++ b/sound/pci/rme9652/hdspm.c
@@ -1838,8 +1838,10 @@ static inline int snd_hdspm_midi_output_possible (struct hdspm *hdspm, int id)
 
 static void snd_hdspm_flush_midi_input(struct hdspm *hdspm, int id)
 {
-	while (snd_hdspm_midi_input_available (hdspm, id))
-		snd_hdspm_midi_read_byte (hdspm, id);
+	int count = 256;
+
+	while (snd_hdspm_midi_input_available(hdspm, id) && --count)
+		snd_hdspm_midi_read_byte(hdspm, id);
 }
 
 static int snd_hdspm_midi_output_write (struct hdspm_midi *hmidi)
-- 
2.43.0