Messages in this thread | | | Date | Mon, 3 Oct 2022 11:39:10 -0700 | From | Kees Cook <> | Subject | Re: [PATCH v2 22/39] mm: Don't allow write GUPs to shadow stack memory |
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On Thu, Sep 29, 2022 at 03:29:19PM -0700, Rick Edgecombe wrote: > [...] > Still allow FOLL_FORCE to write through shadow stack protections, as it > does for read-only protections.
As I asked in the cover letter: why do we need to add this for shstk? It was a mistake for general memory. :P
> [...] > diff --git a/mm/gup.c b/mm/gup.c > index 5abdaf487460..56da98f3335c 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -1043,7 +1043,7 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) > return -EFAULT; > > if (write) { > - if (!(vm_flags & VM_WRITE)) { > + if (!(vm_flags & VM_WRITE) || (vm_flags & VM_SHADOW_STACK)) { > if (!(gup_flags & FOLL_FORCE)) > return -EFAULT; > /*
How about this instead:
return -EFAULT;
if (write) { + if (vm_flags & VM_SHADOW_STACK) + return -EFAULT; if (!(vm_flags & VM_WRITE)) { if (!(gup_flags & FOLL_FORCE)) return -EFAULT;
-- Kees Cook
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