[Bug 1830961] Re: Kernels & kernel drivers fail to build with gcc-9 [error: ‘-mindirect-branch’ and ‘-fcf-protection’ are not compatible]

[Matthias Klose]

no, the kernel infrastructure should handle that like any other
hardening flags before.


** Changed in: gcc-9 (Ubuntu)
       Status: Confirmed => Invalid

** Changed in: gcc-9 (Ubuntu)
   Importance: Critical => Undecided

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Title:
  Kernels & kernel drivers fail to build with gcc-9 [error: ‘-mindirect-
  branch’ and ‘-fcf-protection’ are not compatible]

Status in gcc-9 package in Ubuntu:
  Invalid
Status in linux package in Ubuntu:
  Confirmed
Status in nvidia-graphics-drivers-430 package in Ubuntu:
  Fix Committed
Status in virtualbox package in Ubuntu:
  Confirmed
Status in xtables-addons package in Ubuntu:
  New

Bug description:
  Compiling kernels & kernel modules fails due to these errors:

  ./include/linux/compiler.h:193:1: error: ‘-mindirect-branch’ and
  ‘-fcf-protection’ are not compatible

  (This happens with any kernel modules.)

  This appears to be due to the changes in 9.1.0-3ubuntu1 enabling -fcf-
  protection by default on 19.10's gcc-9.

  Switching to gcc-8 allows compilation to proceed.

  WORKAROUND:

  sudo ln -fs gcc-8 /usr/bin/gcc

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