[PATCH] sound/usb: fix null pointer dereference on pointer cs_desc

[Chengfeng Ye]

The pointer cs_desc return from snd_usb_find_clock_source could
be null, so there is a potential null pointer dereference issue.
Fix this by adding a null check before dereference.

Fixes: 9ec73005 ("ALSA: usb-audio: Refactoring UAC2/3 clock setup code")
Signed-off-by: Chengfeng Ye <cyeaa at connect.ust.hk>
---
 sound/usb/clock.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/sound/usb/clock.c b/sound/usb/clock.c
index 81d5ce07d548..98345a695dcc 100644
--- a/sound/usb/clock.c
+++ b/sound/usb/clock.c
@@ -496,6 +496,10 @@ int snd_usb_set_sample_rate_v2v3(struct snd_usb_audio *chip,
 	union uac23_clock_source_desc *cs_desc;
 
 	cs_desc = snd_usb_find_clock_source(chip, clock, fmt->protocol);
+
+	if (!cs_desc)
+		return 0;
+
 	if (fmt->protocol == UAC_VERSION_3)
 		bmControls = le32_to_cpu(cs_desc->v3.bmControls);
 	else
-- 
2.17.1