CVE-2022-50402 drivers/md/md-bitmap: check the return value of md_bitmap_get_counter()

In the Linux kernel, the following vulnerability has been resolved: drivers/md/md-bitmap: check the return value of mdbitmapgetcounter Check the return value of mdbitmapgetcounter in case it returns NULL pointer, which will result in a null pointer dereference. v2: update the check to include oth...