Messages in this thread | | | Date | Wed, 11 Jul 2018 11:12:32 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC PATCH v2 15/27] mm/mprotect: Prevent mprotect from changing shadow stack |
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On Tue, Jul 10, 2018 at 04:10:08PM -0700, Dave Hansen wrote: > On 07/10/2018 03:26 PM, Yu-cheng Yu wrote: > > Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> > > This still needs a changelog, even if you think it's simple. > > --- a/mm/mprotect.c > > +++ b/mm/mprotect.c > > @@ -446,6 +446,15 @@ static int do_mprotect_pkey(unsigned long start, size_t len, > > error = -ENOMEM; > > if (!vma) > > goto out; > > + > > + /* > > + * Do not allow changing shadow stack memory. > > + */ > > + if (vma->vm_flags & VM_SHSTK) { > > + error = -EINVAL; > > + goto out; > > + } > > + > > I think this is a _bit_ draconian. Why shouldn't we be able to use > protection keys with a shadow stack? Or, set it to PROT_NONE?
Right, and then there's also madvise() and some of the other accessors.
Why do we need to disallow this? AFAICT the worst that can happen is that a process wrecks itself, so what?
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