From: Yu-cheng Yu <yu-cheng.yu@intel.com>
To: Dave Hansen <dave.hansen@intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linux-mm@kvack.org, linux-arch@vger.kernel.org,
linux-api@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
Andy Lutomirski <luto@kernel.org>,
Balbir Singh <bsingharora@gmail.com>,
Borislav Petkov <bp@alien8.de>,
Cyrill Gorcunov <gorcunov@gmail.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Eugene Syromiatnikov <esyr@redhat.com>,
Florian Weimer <fweimer@redhat.com>,
"H.J. Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
Jonathan Corbet <corbet@lwn.net>,
Kees Cook <keescook@chromium.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
Nadav Amit <nadav.amit@gmail.com>,
Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
Peter Zijlstra <peterz@infradead.org>,
Randy Dunlap <rdunlap@infradead.org>,
"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>,
Dave Martin <Dave.Martin@arm.com>,
x86-patch-review@intel.com
Subject: Re: [RFC PATCH v9 14/27] mm: Handle Shadow Stack page fault
Date: Tue, 07 Apr 2020 11:14:58 -0700 [thread overview]
Message-ID: <444d97c4a4f70ccbb12da5e8f7ff498b37a9f60d.camel@intel.com> (raw)
In-Reply-To: <4902a6ee-cb0f-2700-1f6d-9d756593183c@intel.com>
On Wed, 2020-02-26 at 16:08 -0800, Dave Hansen wrote:
> > diff --git a/mm/memory.c b/mm/memory.c
> > index 45442d9a4f52..6daa28614327 100644
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -772,7 +772,8 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
> > * If it's a COW mapping, write protect it both
> > * in the parent and the child
> > */
> > - if (is_cow_mapping(vm_flags) && pte_write(pte)) {
> > + if ((is_cow_mapping(vm_flags) && pte_write(pte)) ||
> > + arch_copy_pte_mapping(vm_flags)) {
> > ptep_set_wrprotect(src_mm, addr, src_pte);
> > pte = pte_wrprotect(pte);
> > }
>
> You have to modify this because pte_write()==0 for shadow stack PTEs, right?
>
> Aren't shadow stack ptes *logically* writable, even if they don't have
> the write bit set? What would happen if we made pte_write()==1 for them?
Here the vm_flags needs to have VM_MAYWRITE, and the PTE needs to have
_PAGE_WRITE. A shadow stack does not have either.
To fix checking vm_flags, what about adding a "arch_is_cow_mappping()" to the
generic is_cow_mapping()?
For the PTE, the check actually tries to determine if the PTE is not already
being copy-on-write, which is:
(!_PAGE_RW && !_PAGE_DIRTY_HW)
So what about making it pte_cow()?
/*
* The PTE is in copy-on-write status.
*/
static inline int pte_cow(pte_t pte)
{
return !(pte_flags(pte) & (_PAGE_WRITE | _PAGE_DIRTY_HW));
}
>
> > @@ -2417,6 +2418,7 @@ static inline void wp_page_reuse(struct vm_fault *vmf)
> > flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
> > entry = pte_mkyoung(vmf->orig_pte);
> > entry = maybe_mkwrite(pte_mkdirty(entry), vma);
> > + entry = pte_set_vma_features(entry, vma);
> > if (ptep_set_access_flags(vma, vmf->address, vmf->pte, entry, 1))
> > update_mmu_cache(vma, vmf->address, vmf->pte);
> > pte_unmap_unlock(vmf->pte, vmf->ptl);
> > @@ -2504,6 +2506,7 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
> > flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
> > entry = mk_pte(new_page, vma->vm_page_prot);
> > entry = maybe_mkwrite(pte_mkdirty(entry), vma);
> > + entry = pte_set_vma_features(entry, vma);
> > /*
> > * Clear the pte entry and flush it first, before updating the
> > * pte with the new entry. This will avoid a race condition
> > @@ -3023,6 +3026,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> > pte = mk_pte(page, vma->vm_page_prot);
> > if ((vmf->flags & FAULT_FLAG_WRITE) && reuse_swap_page(page, NULL)) {
> > pte = maybe_mkwrite(pte_mkdirty(pte), vma);
> > + pte = pte_set_vma_features(pte, vma);
> > vmf->flags &= ~FAULT_FLAG_WRITE;
> > ret |= VM_FAULT_WRITE;
> > exclusive = RMAP_EXCLUSIVE;
> > @@ -3165,6 +3169,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
> > entry = mk_pte(page, vma->vm_page_prot);
> > if (vma->vm_flags & VM_WRITE)
> > entry = pte_mkwrite(pte_mkdirty(entry));
> > + entry = pte_set_vma_features(entry, vma);
> >
> > vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address,
> > &vmf->ptl);
> >
>
> These seem wrong, or at best inconsistent with what's already done.
>
> We don't need anything like pte_set_vma_features() today because we have
> vma->vm_page_prot. We could easily have done what you suggest here for
> things like protection keys: ignore the pkey PTE bits until we create
> the final PTE then shove them in there.
>
> What are the bit patterns of the shadow stack bits that come out of
> these sites? Can they be represented in ->vm_page_prot?
Yes, we can put _PAGE_DIRTY_HW in vm_page_prot. Also set the bit in
ptep_set_access_flags() for shadow stack PTEs.
next prev parent reply other threads:[~2020-04-07 18:15 UTC|newest]
Thread overview: 107+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-05 18:19 [RFC PATCH v9 00/27] Control-flow Enforcement: Shadow Stack Yu-cheng Yu
2020-02-05 18:19 ` [RFC PATCH v9 01/27] Documentation/x86: Add CET description Yu-cheng Yu
2020-02-06 0:16 ` Randy Dunlap
2020-02-06 20:17 ` Yu-cheng Yu
2020-02-25 20:02 ` Kees Cook
2020-02-28 15:55 ` Yu-cheng Yu
2020-02-26 17:57 ` Dave Hansen
2020-03-09 17:00 ` Yu-cheng Yu
2020-03-09 17:21 ` Dave Hansen
2020-03-09 19:27 ` Yu-cheng Yu
2020-03-09 19:35 ` Dave Hansen
2020-03-09 19:50 ` H.J. Lu
2020-03-09 20:16 ` Andy Lutomirski
2020-03-09 20:54 ` H.J. Lu
2020-03-09 20:59 ` Dave Hansen
2020-03-09 21:12 ` H.J. Lu
2020-03-09 22:02 ` Andy Lutomirski
2020-03-09 22:19 ` Dave Hansen
2020-03-09 23:11 ` H.J. Lu
2020-03-09 23:20 ` Dave Hansen
2020-03-09 23:51 ` H.J. Lu
2020-03-09 23:59 ` Andy Lutomirski
2020-03-10 0:08 ` H.J. Lu
2020-03-10 1:21 ` Andy Lutomirski
2020-03-10 2:13 ` H.J. Lu
2020-02-05 18:19 ` [RFC PATCH v9 02/27] x86/cpufeatures: Add CET CPU feature flags for Control-flow Enforcement Technology (CET) Yu-cheng Yu
2020-02-25 20:02 ` Kees Cook
2020-02-05 18:19 ` [RFC PATCH v9 03/27] x86/fpu/xstate: Introduce CET MSR XSAVES supervisor states Yu-cheng Yu
2020-02-25 20:04 ` Kees Cook
2020-02-05 18:19 ` [RFC PATCH v9 04/27] x86/cet: Add control-protection fault handler Yu-cheng Yu
2020-02-25 20:06 ` Kees Cook
2020-02-26 17:10 ` Dave Hansen
2020-03-05 20:44 ` Yu-cheng Yu
2020-02-05 18:19 ` [RFC PATCH v9 05/27] x86/cet/shstk: Add Kconfig option for user-mode Shadow Stack protection Yu-cheng Yu
2020-02-25 20:07 ` Kees Cook
2020-02-26 17:03 ` Dave Hansen
2020-02-26 19:57 ` Pavel Machek
2020-03-05 20:38 ` Yu-cheng Yu
2020-02-26 18:05 ` Dave Hansen
2020-02-27 1:02 ` H.J. Lu
2020-02-27 1:16 ` Dave Hansen
2020-02-27 2:11 ` H.J. Lu
2020-02-27 3:57 ` Andy Lutomirski
2020-02-27 18:03 ` Dave Hansen
2020-03-06 18:37 ` Yu-cheng Yu
2020-03-06 19:02 ` Dave Hansen
2020-03-06 21:16 ` Yu-cheng Yu
2020-02-05 18:19 ` [RFC PATCH v9 06/27] mm: Introduce VM_SHSTK for Shadow Stack memory Yu-cheng Yu
2020-02-25 20:07 ` Kees Cook
2020-02-26 18:07 ` Dave Hansen
2020-02-05 18:19 ` [RFC PATCH v9 07/27] Add guard pages around a Shadow Stack Yu-cheng Yu
2020-02-25 20:11 ` Kees Cook
2020-02-26 18:17 ` Dave Hansen
2020-02-05 18:19 ` [RFC PATCH v9 08/27] x86/mm: Change _PAGE_DIRTY to _PAGE_DIRTY_HW Yu-cheng Yu
2020-02-25 20:12 ` Kees Cook
2020-02-26 18:20 ` Dave Hansen
2020-02-05 18:19 ` [RFC PATCH v9 09/27] x86/mm: Introduce _PAGE_DIRTY_SW Yu-cheng Yu
2020-02-25 20:12 ` Kees Cook
2020-02-26 21:35 ` Dave Hansen
2020-04-01 19:08 ` Yu-cheng Yu
2020-04-01 19:22 ` Dave Hansen
2020-02-05 18:19 ` [RFC PATCH v9 10/27] x86/mm: Update pte_modify, pmd_modify, and _PAGE_CHG_MASK for _PAGE_DIRTY_SW Yu-cheng Yu
2020-02-26 22:02 ` Dave Hansen
2020-02-05 18:19 ` [RFC PATCH v9 11/27] drm/i915/gvt: Change _PAGE_DIRTY to _PAGE_DIRTY_BITS Yu-cheng Yu
2020-02-25 20:13 ` Kees Cook
2020-02-26 22:04 ` Dave Hansen
2020-04-03 15:42 ` Yu-cheng Yu
2020-02-05 18:19 ` [RFC PATCH v9 12/27] x86/mm: Modify ptep_set_wrprotect and pmdp_set_wrprotect for _PAGE_DIRTY_SW Yu-cheng Yu
2020-02-25 20:14 ` Kees Cook
2020-02-26 22:20 ` Dave Hansen
2020-02-05 18:19 ` [RFC PATCH v9 13/27] x86/mm: Shadow Stack page fault error checking Yu-cheng Yu
2020-02-25 20:16 ` Kees Cook
2020-02-26 22:47 ` Dave Hansen
2020-02-05 18:19 ` [RFC PATCH v9 14/27] mm: Handle Shadow Stack page fault Yu-cheng Yu
2020-02-25 20:20 ` Kees Cook
2020-03-05 18:30 ` Yu-cheng Yu
2020-02-27 0:08 ` Dave Hansen
2020-04-07 18:14 ` Yu-cheng Yu [this message]
2020-04-07 22:21 ` Dave Hansen
2020-04-08 18:18 ` Yu-cheng Yu
2020-02-05 18:19 ` [RFC PATCH v9 15/27] mm: Handle THP/HugeTLB " Yu-cheng Yu
2020-02-25 20:59 ` Kees Cook
2020-03-13 22:00 ` Yu-cheng Yu
2020-02-05 18:19 ` [RFC PATCH v9 16/27] mm: Update can_follow_write_pte() for Shadow Stack Yu-cheng Yu
2020-02-27 0:34 ` Dave Hansen
2020-02-05 18:19 ` [RFC PATCH v9 17/27] x86/cet/shstk: User-mode Shadow Stack support Yu-cheng Yu
2020-02-25 21:07 ` Kees Cook
2020-02-27 0:55 ` Dave Hansen
2020-02-05 18:19 ` [RFC PATCH v9 18/27] x86/cet/shstk: Introduce WRUSS instruction Yu-cheng Yu
2020-02-25 21:10 ` Kees Cook
2020-03-05 18:39 ` Yu-cheng Yu
2020-02-05 18:19 ` [RFC PATCH v9 19/27] x86/cet/shstk: Handle signals for Shadow Stack Yu-cheng Yu
2020-02-25 21:17 ` Kees Cook
2020-02-05 18:19 ` [RFC PATCH v9 20/27] ELF: UAPI and Kconfig additions for ELF program properties Yu-cheng Yu
2020-02-05 18:19 ` [RFC PATCH v9 21/27] binfmt_elf: Define GNU_PROPERTY_X86_FEATURE_1_AND Yu-cheng Yu
2020-02-25 21:18 ` Kees Cook
2020-02-05 18:19 ` [RFC PATCH v9 22/27] ELF: Add ELF program property parsing support Yu-cheng Yu
2020-02-25 21:20 ` Kees Cook
2020-02-05 18:19 ` [RFC PATCH v9 23/27] ELF: Introduce arch_setup_elf_property() Yu-cheng Yu
2020-02-05 18:19 ` [RFC PATCH v9 24/27] x86/cet/shstk: ELF header parsing for Shadow Stack Yu-cheng Yu
2020-02-25 21:22 ` Kees Cook
2020-02-05 18:19 ` [RFC PATCH v9 25/27] x86/cet/shstk: Handle thread " Yu-cheng Yu
2020-02-25 21:29 ` Kees Cook
2020-03-25 21:51 ` Yu-cheng Yu
2020-02-05 18:19 ` [RFC PATCH v9 26/27] mm/mmap: Add Shadow Stack pages to memory accounting Yu-cheng Yu
2020-02-05 18:19 ` [RFC PATCH v9 27/27] x86/cet/shstk: Add arch_prctl functions for Shadow Stack Yu-cheng Yu
2020-02-25 21:31 ` [RFC PATCH v9 00/27] Control-flow Enforcement: " Kees Cook
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