[PATCH] ALSA: hda: cs35l41: Fix NULL pointer dereference in cs35l41_get_acpi_mute_state()

[Denis Arefev <arefev@swemel.ru>]

Return value of a function acpi_evaluate_dsm() is dereferenced  without
checking for NULL, but it is usually checked for this function.

acpi_evaluate_dsm() may return NULL, when acpi_evaluate_object() returns
acpi_status other than ACPI_SUCCESS, so add a check to prevent the crach.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 447106e92a0c ("ALSA: hda: cs35l41: Support mute notifications for CS35L41 HDA")
Cc: stable@vger.kernel.org
Signed-off-by: Denis Arefev <arefev@swemel.ru>
---
 sound/hda/codecs/side-codecs/cs35l41_hda.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sound/hda/codecs/side-codecs/cs35l41_hda.c b/sound/hda/codecs/side-codecs/cs35l41_hda.c
index 37f2cdc8ce82..890ddb8cc66c 100644
--- a/sound/hda/codecs/side-codecs/cs35l41_hda.c
+++ b/sound/hda/codecs/side-codecs/cs35l41_hda.c
@@ -1426,6 +1426,8 @@ static int cs35l41_get_acpi_mute_state(struct cs35l41_hda *cs35l41, acpi_handle
 
 	if (cs35l41_dsm_supported(handle, CS35L41_DSM_GET_MUTE)) {
 		ret = acpi_evaluate_dsm(handle, &guid, 0, CS35L41_DSM_GET_MUTE, NULL);
+		if (!ret)
+			return -EINVAL;
 		mute = *ret->buffer.pointer;
 		dev_dbg(cs35l41->dev, "CS35L41_DSM_GET_MUTE: %d\n", mute);
 	}
-- 
2.43.0