[PATCH] ALSA: hda/hdmi: clamp num_cvts against cvt_nids[] in hdmi_read_pin_conn

[Peter Ujfalusi <peter.ujfalusi@linux.intel.com>]

hdmi_add_cvt() stores each converter's NID into the fixed-size
spec->cvt_nids[] array (used only by the Intel Haswell pin-connection
fixup), but only when spec->num_cvts is still within
ARRAY_SIZE(cvt_nids); the num_cvts counter itself is incremented
unconditionally regardless of whether the store happened. A codec
that reports more converters than cvt_nids[] can hold therefore ends
up with num_cvts > ARRAY_SIZE(cvt_nids).

hdmi_read_pin_conn(), on the intel_hsw_fixup path, copies num_cvts
elements from cvt_nids[] with memcpy(), so once num_cvts exceeds the
array size this reads past cvt_nids[] and writes the resulting
garbage NIDs into per_pin->mux_nids[].

Clamp the copy length to the actual size of cvt_nids[] instead of
trusting num_cvts, which is also used unbounded as the size of the
separate, dynamically-sized spec->cvts array and must not be
truncated at the source.

Fixes: bce0d2a80e42 ("ALSA: hda - Allow unlimited pins and converters in patch_hdmi.c")
Cc: stable@vger.kernel.org
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
---
 sound/hda/codecs/hdmi/hdmi.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/sound/hda/codecs/hdmi/hdmi.c b/sound/hda/codecs/hdmi/hdmi.c
index a8aac0b36c73..355fd3e73183 100644
--- a/sound/hda/codecs/hdmi/hdmi.c
+++ b/sound/hda/codecs/hdmi/hdmi.c
@@ -983,7 +983,8 @@ static int hdmi_read_pin_conn(struct hda_codec *codec, int pin_idx)
 	snd_hda_set_dev_select(codec, pin_nid, dev_id);
 
 	if (spec->intel_hsw_fixup) {
-		conns = spec->num_cvts;
+		/* spec->cvt_nids[] only has ARRAY_SIZE(spec->cvt_nids) slots */
+		conns = min_t(int, spec->num_cvts, ARRAY_SIZE(spec->cvt_nids));
 		memcpy(per_pin->mux_nids, spec->cvt_nids,
 		       sizeof(hda_nid_t) * conns);
 	} else {
-- 
2.56.0