| Message ID | 20210401221104.31584-21-yu-cheng.yu@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v24,01/30] Documentation/x86: Add CET description | expand |
On Thu, Apr 01, 2021 at 03:10:54PM -0700, Yu-cheng Yu wrote: > In change_pte_range(), when a PTE is changed for prot_numa, _PAGE_RW is > preserved to avoid the additional write fault after the NUMA hinting fault. > However, pte_write() now includes both normal writable and shadow stack > (RW=0, Dirty=1) PTEs, but the latter does not have _PAGE_RW and has no need > to preserve it. > > Exclude shadow stack from preserve_write test, and apply the same change to > change_huge_pmd(). > > Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> > Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > --- > v24: > - Change arch_shadow_stack_mapping() to is_shadow_stack_mapping(). > > mm/huge_memory.c | 7 ++++++- > mm/mprotect.c | 9 ++++++++- > 2 files changed, 14 insertions(+), 2 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 65fc0aedd577..1d41138c4f74 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1812,12 +1812,17 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, > bool prot_numa = cp_flags & MM_CP_PROT_NUMA; > bool uffd_wp = cp_flags & MM_CP_UFFD_WP; > bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE; > + bool shstk = is_shadow_stack_mapping(vma->vm_flags); > > ptl = __pmd_trans_huge_lock(pmd, vma); > if (!ptl) > return 0; > > - preserve_write = prot_numa && pmd_write(*pmd); > + /* > + * Preserve only normal writable huge PMD, but not shadow > + * stack (RW=0, Dirty=1). > + */ > + preserve_write = prot_numa && pmd_write(*pmd) && !shstk; New variable seems unnecessary. What about just: if (is_shadow_stack_mapping(vma->vm_flags)) preserve_write = false; ? > ret = 1; > > #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION > diff --git a/mm/mprotect.c b/mm/mprotect.c > index c1ce78d688b6..550448dc5ff1 100644 > --- a/mm/mprotect.c > +++ b/mm/mprotect.c > @@ -75,7 +75,14 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, > oldpte = *pte; > if (pte_present(oldpte)) { > pte_t ptent; > - bool preserve_write = prot_numa && pte_write(oldpte); > + bool shstk = is_shadow_stack_mapping(vma->vm_flags); > + bool preserve_write; > + > + /* > + * Preserve only normal writable PTE, but not shadow > + * stack (RW=0, Dirty=1). > + */ > + preserve_write = prot_numa && pte_write(oldpte) && !shstk; Ditto. > > /* > * Avoid trapping faults against the zero or KSM > -- > 2.21.0 > >
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 65fc0aedd577..1d41138c4f74 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1812,12 +1812,17 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, bool prot_numa = cp_flags & MM_CP_PROT_NUMA; bool uffd_wp = cp_flags & MM_CP_UFFD_WP; bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE; + bool shstk = is_shadow_stack_mapping(vma->vm_flags); ptl = __pmd_trans_huge_lock(pmd, vma); if (!ptl) return 0; - preserve_write = prot_numa && pmd_write(*pmd); + /* + * Preserve only normal writable huge PMD, but not shadow + * stack (RW=0, Dirty=1). + */ + preserve_write = prot_numa && pmd_write(*pmd) && !shstk; ret = 1; #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION diff --git a/mm/mprotect.c b/mm/mprotect.c index c1ce78d688b6..550448dc5ff1 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -75,7 +75,14 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, oldpte = *pte; if (pte_present(oldpte)) { pte_t ptent; - bool preserve_write = prot_numa && pte_write(oldpte); + bool shstk = is_shadow_stack_mapping(vma->vm_flags); + bool preserve_write; + + /* + * Preserve only normal writable PTE, but not shadow + * stack (RW=0, Dirty=1). + */ + preserve_write = prot_numa && pte_write(oldpte) && !shstk; /* * Avoid trapping faults against the zero or KSM
In change_pte_range(), when a PTE is changed for prot_numa, _PAGE_RW is preserved to avoid the additional write fault after the NUMA hinting fault. However, pte_write() now includes both normal writable and shadow stack (RW=0, Dirty=1) PTEs, but the latter does not have _PAGE_RW and has no need to preserve it. Exclude shadow stack from preserve_write test, and apply the same change to change_huge_pmd(). Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> --- v24: - Change arch_shadow_stack_mapping() to is_shadow_stack_mapping(). mm/huge_memory.c | 7 ++++++- mm/mprotect.c | 9 ++++++++- 2 files changed, 14 insertions(+), 2 deletions(-)