Describe CVE-2021-47521.
What is CVE-2021-47521?
In the Linux kernel, the following vulnerability has been resolved:

can: sja1000: fix use after free in ems_pcmcia_add_card()

If the last channel is not available then "dev" is freed.  Fortunately,
we can just use "pdev->irq" instead.

Also we should check if at least one channel was set up..