CVE-2021-47289

In the Linux kernel, the following vulnerability has been resolved: ACPI:
fix NULL pointer dereference Commit 71f642833284 (“ACPI: utils: Fix
reference counting in for_each_acpi_dev_match()”) started doing
“acpi_dev_put()” on a pointer that was possibly NULL. That fails miserably,
because that helper inline function is not set up to handle that case. Just
make acpi_dev_put() silently accept a NULL pointer, rather than calling
down to put_device() with an invalid offset off that NULL pointer.