[PATCH 5.10.y] ALSA: hda/hdmi: clamp sad_count in ELD proc write handler

[Sasha Levin <sashal@kernel.org>]

From: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>

[ Upstream commit b3e7ddd694f8429217ba509b55b910a0e4361dfb ]

snd_hdmi_write_eld_info() parses a "sad_count N" line from the
root-writable ELD proc interface and assigns N directly to
e->sad_count with no upper bound, unlike the per-index "sadN_*" lines
a few lines below which are already bounded to ELD_MAX_SAD.

snd_hdmi_eld_update_pcm_info() later iterates
"for (i = 0; i < e->sad_count; i++)" over the fixed
e->sad[ELD_MAX_SAD] array, so an oversized sad_count read from the
proc file causes it to walk past the array.

Reject sad_count values above ELD_MAX_SAD, matching the existing
per-index guard.

Fixes: acb059938810 ("ALSA: hda - ELD proc interface write updates")
Cc: stable@vger.kernel.org
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Link: https://patch.msgid.link/20261008085133.9528-1-peter.ujfalusi@linux.intel.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
[ sashal: adjusted for the older source file location of the HDMI ELD code ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 sound/pci/hda/hda_eld.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/sound/pci/hda/hda_eld.c b/sound/pci/hda/hda_eld.c
index 136477ed46ae2..5d2f48b5d7166 100644
--- a/sound/pci/hda/hda_eld.c
+++ b/sound/pci/hda/hda_eld.c
@@ -521,9 +521,11 @@ void snd_hdmi_write_eld_info(struct hdmi_eld *eld,
 			e->aud_synch_delay = val;
 		else if (!strcmp(name, "speakers"))
 			e->spk_alloc = val;
-		else if (!strcmp(name, "sad_count"))
+		else if (!strcmp(name, "sad_count")) {
+			if (val > ELD_MAX_SAD)
+				continue;
 			e->sad_count = val;
-		else if (!strncmp(name, "sad", 3)) {
+		} else if (!strncmp(name, "sad", 3)) {
 			sname = name + 4;
 			n = name[3] - '0';
 			if (name[4] >= '0' && name[4] <= '9') {
-- 
2.53.0