[PATCH v29 21/32] mm/mprotect: Exclude shadow stack from preserve_write
From: Yu-cheng Yu <hidden>
Date: 2021-08-20 18:21:21
Also in:
linux-arch, linux-doc, linux-mm, lkml
Subsystem:
memory management, memory management - thp (transparent huge page), memory mapping, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Lorenzo Stoakes, Liam R. Howlett, Linus Torvalds
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 <redacted> Reviewed-by: Kirill A. Shutemov <redacted> --- v25: - Move is_shadow_stack_mapping() to a separate line. v24: - Change arch_shadow_stack_mapping() to is_shadow_stack_mapping(). --- mm/huge_memory.c | 7 +++++++ mm/mprotect.c | 7 +++++++ 2 files changed, 14 insertions(+)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index d35acb59dde9..bb38ecdf992f 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c@@ -1776,6 +1776,13 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, return 0; preserve_write = prot_numa && pmd_write(*pmd); + + /* + * Preserve only normal writable huge PMD, but not shadow + * stack (RW=0, Dirty=1). + */ + 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 9b424f2fd3a9..94cb799216ec 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c@@ -77,6 +77,13 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, 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 (is_shadow_stack_mapping(vma->vm_flags)) + preserve_write = false; + /* * Avoid trapping faults against the zero or KSM * pages. See similar comment in change_huge_pmd.
--
2.21.0