Status check: dropped CONFIG_X86_USER_SHADOW_STACK fix in vdso Makefile (a48acbaf99d2)

[Tobias Jakobsen]

Hi all,

Following up on commit a48acbaf99d2 ("x86/entry/vdso: Fix filtering
of vdso compiler flags", Jan 16 2026). That commit fixed two of the
three typos Chris's AI review found, but deliberately left one out:

  "Chris's script also found that CONFIG_X86_USER_SHADOW_STACK was
  missing CONFIG_, but it needs a different fix."

  [ dhansen: remove CONFIG_X86_USER_SHADOW_STACK munging, add
    mention in changelog. ]

The kernel test robot found that fixing it directly exposes a real
-mindirect-branch/-fcf-protection incompatibility elsewhere in the
build (Closes: https://lore.kernel.org/r/202601180025.lLCHWiad-lkp@xxxxxxxxx/).

Checked against the current tree, in arch/x86/entry/vdso/common/
Makefile.include:48 it is unfixed:
  flags-$(X86_USER_SHADOW_STACK) += $(call cc-option, -fcf-protection=return)

Still missing CONFIG_ so it's a no-op under any config.

Without the note being added the auto enable does not fire at all.
Is anyone working on the retpoline/cf-protection fix this was
waiting on? If there is a patch to test I'm happy to help out!

Thank you,
Tobias.