kernel: mm/vmemmap/devdax: fix kernel crash when probing devdax devices

A flaw was discovered in the device DAX devdax probing implementation of the Linux kernel memory management subsystem mm/vmemmap/devdax. Under specific architecture configurations for example POWER9 with hash MMU, the code path in vmemmappopulatecompoundpages did not properly account for...

UBUNTU-CVE-2019-15847

The POWER9 backend in GNU Compiler Collection GCC before version 10 could optimize multiple calls of the builtindarn intrinsic into a single call, thus reducing the entropy of the random number generator. This occurred because a volatile operation was not specified. For example, within a single...