GCC: Flawed Code Generation

Background

The GNU Compiler Collection includes front ends for C, C++, Objective-C, Fortran, Ada, Go, D and Modula-2 as well as libraries for these languages (libstdc++,…).

Description

A vulnerability has been discovered in GCC. Please review the CVE identifier referenced below for details.

Impact

The POWER9 backend in GNU Compiler Collection (GCC) could optimize multiple calls of the __builtin_darn 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 execution of a program, the output of every __builtin_darn() call may be the same.

Workaround

There is no known workaround at this time.

Resolution

All GCC users should upgrade to the latest version:

 # emerge --sync
 # emerge --ask --oneshot --verbose ">=sys-devel/gcc-10.0"

And then select it with gcc-config:

 # gcc-config latest

In this case, users should also rebuild all affected packages with emerge -e, e.g.:

 # emerge --usepkg=n --emptytree @world