Hi,
On Tue, 2025-02-25 at 06:22 +0000, Lorenzo Stoakes wrote:
> On Mon, Feb 24, 2025 at 10:52:44PM +0000, jeffxu@xxxxxxxxxxxx wrote:
> > From: Jeff Xu <jeffxu@xxxxxxxxxxxx>
> >
> > Provide support for CONFIG_MSEAL_SYSTEM_MAPPINGS on UML, covering
> > the vdso.
> >
> > Testing passes on UML.
>
> Maybe expand on this by stating that it has been confirmed by Benjamin (I
> _believe_) that UML has no need for problematic relocation so this is known to
> be good.
I may well be misreading this message, but this sounds to me that this
is a misinterpretation. So, just to clarify in case that is needed.
CONFIG_MSEAL_SYSTEM_MAPPINGS does work fine for the UML kernel.
However, the UML kernel is a normal userspace application itself and
for this application to run, the host kernel must have the feature
disabled.
So, UML supports the feature. But it still *cannot* run on a host
machine that has the feature enabled.
Benjamin
>
> >
> > Signed-off-by: Jeff Xu <jeffxu@xxxxxxxxxxxx>
> > Tested-by: Benjamin Berg <benjamin.berg@xxxxxxxxx>
>
> Anyway I know UML has at any rate been confirmed to be good to go +
> patch looks
> fine, so:
>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
>
> > ---
> > arch/um/Kconfig | 1 +
> > arch/x86/um/vdso/vma.c | 6 ++++--
> > 2 files changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/um/Kconfig b/arch/um/Kconfig
> > index 18051b1cfce0..eb2d439a5334 100644
> > --- a/arch/um/Kconfig
> > +++ b/arch/um/Kconfig
> > @@ -10,6 +10,7 @@ config UML
> > select ARCH_HAS_FORTIFY_SOURCE
> > select ARCH_HAS_GCOV_PROFILE_ALL
> > select ARCH_HAS_KCOV
> > + select ARCH_HAS_MSEAL_SYSTEM_MAPPINGS
> > select ARCH_HAS_STRNCPY_FROM_USER
> > select ARCH_HAS_STRNLEN_USER
> > select HAVE_ARCH_AUDITSYSCALL
> > diff --git a/arch/x86/um/vdso/vma.c b/arch/x86/um/vdso/vma.c
> > index f238f7b33cdd..fdfba858ffc9 100644
> > --- a/arch/x86/um/vdso/vma.c
> > +++ b/arch/x86/um/vdso/vma.c
> > @@ -54,6 +54,7 @@ int arch_setup_additional_pages(struct
> > linux_binprm *bprm, int uses_interp)
> > {
> > struct vm_area_struct *vma;
> > struct mm_struct *mm = current->mm;
> > + unsigned long vm_flags;
> > static struct vm_special_mapping vdso_mapping = {
> > .name = "[vdso]",
> > };
> > @@ -65,9 +66,10 @@ int arch_setup_additional_pages(struct
> > linux_binprm *bprm, int uses_interp)
> > return -EINTR;
> >
> > vdso_mapping.pages = vdsop;
> > + vm_flags =
> > VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC;
> > + vm_flags |= VM_SEALED_SYSMAP;
> > vma = _install_special_mapping(mm, um_vdso_addr,
> > PAGE_SIZE,
> > - VM_READ|VM_EXEC|
> > - VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
> > + vm_flags,
> > &vdso_mapping);
> >
> > mmap_write_unlock(mm);
> > --
> > 2.48.1.658.g4767266eb4-goog
> >
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