On Fri, Nov 04, 2022 at 03:35:47PM -0700, Rick Edgecombe wrote: > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 73b9b78f8cf4..7643a4db1b50 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1803,6 +1803,13 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, > return 0; > > preserve_write = prot_numa && pmd_write(*pmd); > + > + /* > + * Preserve only normal writable huge PMD, but not shadow > + * stack (RW=0, Dirty=1). > + */ > + if (vma->vm_flags & VM_SHADOW_STACK) > + preserve_write = false; > ret = 1; > > #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION > diff --git a/mm/mprotect.c b/mm/mprotect.c > index 668bfaa6ed2a..ea82ce5f38fe 100644 > --- a/mm/mprotect.c > +++ b/mm/mprotect.c > @@ -115,6 +115,13 @@ static unsigned long change_pte_range(struct mmu_gather *tlb, > pte_t ptent; > bool preserve_write = prot_numa && pte_write(oldpte); > > + /* > + * Preserve only normal writable PTE, but not shadow > + * stack (RW=0, Dirty=1). > + */ > + if (vma->vm_flags & VM_SHADOW_STACK) > + preserve_write = false; > + > /* > * Avoid trapping faults against the zero or KSM > * pages. See similar comment in change_huge_pmd. These comments lack a why component; someone is going to wonder wtf this code is doing in the near future -- that someone might be you.
