Describe CVE-2021-47211.
What is CVE-2021-47211?
In the Linux kernel, the following vulnerability has been resolved:

ALSA: usb-audio: fix null pointer dereference on pointer cs_desc

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..