[PATCH 2/9] ALSA: hda: Fix null-ptr-deref when i915 fails and hdmi is denylisted

[Cezary Rojewski]

If snd_hda_hdmi_codec module is denylisted and any event causes i915
enumeration to fail, is_likely_hdmi_codec() ends in null-ptr-deref.

As snd_soc_hda is an ASoC-based driver, its initialization is delayed
until all the necessary components appear in the system - allowing
actual sound card to enumerate. snd_hda_codec_configure() gets called by
the avs-driver core during probe_codecs() but the
snd_hda_codec_device_new(), necessary to complete codecs initialization,
happens only when codec-component of hda sound card is being probed.

Denylisting snd_hda_codec_hdmi module causes snd_hda_codec_configure()
to reach: codec_bind_generic() -> is_likely_hdmi_codec() which makes use
of ->wcaps and at this point the it isn't initialized yet - again,
requires completion of snd_hda_codec_device_new().

Signed-off-by: Cezary Rojewski <cezary.rojewski at intel.com>
---
 sound/pci/hda/hda_bind.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/sound/pci/hda/hda_bind.c b/sound/pci/hda/hda_bind.c
index c572fb5886d5..cae9a975cbcc 100644
--- a/sound/pci/hda/hda_bind.c
+++ b/sound/pci/hda/hda_bind.c
@@ -248,6 +248,13 @@ static bool is_likely_hdmi_codec(struct hda_codec *codec)
 {
 	hda_nid_t nid;
 
+	/*
+	 * For ASoC users, if snd_hda_hdmi_codec module is denylisted and any
+	 * event causes i915 enumeration to fail, ->wcaps remains uninitialized.
+	 */
+	if (!codec->wcaps)
+		return true;
+
 	for_each_hda_codec_node(nid, codec) {
 		unsigned int wcaps = get_wcaps(codec, nid);
 		switch (get_wcaps_type(wcaps)) {
-- 
2.25.1