ALSA: usb-audio: WARN_ON when alts is passed as NULL

Prevent NULL dereference in snd_usb_add_endpoints(), when
alts is passed as NULL. In this case, WARN (since this is
a non-fatal bug) and return NULL ep. Call sites treat a NULL
return value as an error.

Signed-off-by: Eldad Zack <eldad@fogrefinery.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 3 insertions, 0 deletions

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 7a444b5501d9..92ea945ff486 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -418,6 +418,9 @@ struct snd_usb_endpoint *snd_usb_add_endpoint(struct snd_usb_audio *chip,
         struct snd_usb_endpoint *ep;
         int is_playback = direction == SNDRV_PCM_STREAM_PLAYBACK;
 
+        if (WARN_ON(!alts))
+                return NULL;
+
         mutex_lock(&chip->mutex);
 
         list_for_each_entry(ep, &chip->ep_list, list) {