Re: [PATCH v7 3/7] mseal, system mappings: enable x86-64

[Jeff Xu <jeffxu@chromium.org>]

On Mon, Feb 24, 2025 at 5:03 PM Kees Cook <kees@kernel.org> wrote:
>
> On Mon, Feb 24, 2025 at 10:52:42PM +0000, jeffxu@chromium.org wrote:
> > From: Jeff Xu <jeffxu@chromium.org>
> >
> > Provide support for CONFIG_MSEAL_SYSTEM_MAPPINGS on x86-64,
> > covering the vdso, vvar, vvar_vclock.
> >
> > Production release testing passes on Android and Chrome OS.
> >
> > Signed-off-by: Jeff Xu <jeffxu@chromium.org>
> > ---
> >  arch/x86/Kconfig          |  1 +
> >  arch/x86/entry/vdso/vma.c | 16 ++++++++++------
> >  2 files changed, 11 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> > index 87198d957e2f..8fa17032ca46 100644
> > --- a/arch/x86/Kconfig
> > +++ b/arch/x86/Kconfig
> > @@ -26,6 +26,7 @@ config X86_64
> >       depends on 64BIT
> >       # Options that are inherently 64-bit kernel only:
> >       select ARCH_HAS_GIGANTIC_PAGE
> > +     select ARCH_HAS_MSEAL_SYSTEM_MAPPINGS
> >       select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
> >       select ARCH_SUPPORTS_PER_VMA_LOCK
> >       select ARCH_SUPPORTS_HUGE_PFNMAP if TRANSPARENT_HUGEPAGE
> > diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
> > index 39e6efc1a9ca..1b1c009f20a8 100644
> > --- a/arch/x86/entry/vdso/vma.c
> > +++ b/arch/x86/entry/vdso/vma.c
> > @@ -247,6 +247,7 @@ static int map_vdso(const struct vdso_image *image, unsigned long addr)
> >       struct mm_struct *mm = current->mm;
> >       struct vm_area_struct *vma;
> >       unsigned long text_start;
> > +     unsigned long vm_flags;
> >       int ret = 0;
> >
> >       if (mmap_write_lock_killable(mm))
> > @@ -264,11 +265,12 @@ static int map_vdso(const struct vdso_image *image, unsigned long addr)
> >       /*
> >        * MAYWRITE to allow gdb to COW and set breakpoints
> >        */
> > +     vm_flags = VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC;
> > +     vm_flags |= VM_SEALED_SYSMAP;
> >       vma = _install_special_mapping(mm,
> >                                      text_start,
> >                                      image->size,
> > -                                    VM_READ|VM_EXEC|
> > -                                    VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
> > +                                    vm_flags,
> >                                      &vdso_mapping);
>
> I think these (in all patches) were supposed to be reworked without the
> "vm_flags" variable addition?
>
OK.

> --
> Kees Cook