In the Linux kernel, the following vulnerability has been resolved:
mm: prevent derefencing NULL ptr in pfnsectionvalid()
Commit 5ec8e8ea8b77 ("mm/sparsemem: fix race in accessing memorysection->usage") changed pfnsectionvalid() to add a READONCE() call around "ms->usage" to fix a race with sectiondeactivate() where ms->usage can be cleared. The READONCE() call, by itself, is not enough to prevent NULL pointer dereference. We need to check its value before dereferencing it.