[PATCH v19 15/25] mm: Fixup places that call pte_mkwrite() directly

Yu-cheng Yu
2021-02-03T22:57:14Z

When serving a page fault, maybe_mkwrite() makes a PTE writable if it is in
a writable vma. A shadow stack vma is writable, but its PTEs need
_PAGE_DIRTY to be set to become writable. For this reason, maybe_mkwrite()
has been updated.

There are a few places that call pte_mkwrite() directly, but effect the
same result as from maybe_mkwrite(). These sites need to be updated for
shadow stack as well. Thus, change them to maybe_mkwrite():

- do_anonymous_page() and migrate_vma_insert_page() check VM_WRITE directly
and call pte_mkwrite(), which is the same as maybe_mkwrite(). Change
them to maybe_mkwrite().

- In do_numa_page(), if the numa entry 'was-writable', then pte_mkwrite()
is called directly. Fix it by doing maybe_mkwrite().

- In change_pte_range(), pte_mkwrite() is called directly. Replace it with
maybe_mkwrite().

A shadow stack vma is writable but has different vma
flags, and handled accordingly in maybe_mkwrite().

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
---
mm/memory.c | 5 ++---
mm/migrate.c | 3 +--
mm/mprotect.c | 2 +-
3 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index feff48e1465a..1de649c61013 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3549,8 +3549,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)

entry = mk_pte(page, vma->vm_page_prot);
entry = pte_sw_mkyoung(entry);
- if (vma->vm_flags & VM_WRITE)
- entry = pte_mkwrite(pte_mkdirty(entry));
+ entry = maybe_mkwrite(pte_mkdirty(entry), vma);

vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address,
&vmf->ptl);
@@ -4205,7 +4204,7 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
pte = pte_modify(old_pte, vma->vm_page_prot);
pte = pte_mkyoung(pte);
if (was_writable)
- pte = pte_mkwrite(pte);
+ pte = maybe_mkwrite(pte, vma);
ptep_modify_prot_commit(vma, vmf->address, vmf->pte, old_pte, pte);
update_mmu_cache(vma, vmf->address, vmf->pte);

diff --git a/mm/migrate.c b/mm/migrate.c
index c0efe921bca5..8878d75c0db7 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2964,8 +2964,7 @@ static void migrate_vma_insert_page(struct migrate_vma *migrate,
}
} else {
entry = mk_pte(page, vma->vm_page_prot);
- if (vma->vm_flags & VM_WRITE)
- entry = pte_mkwrite(pte_mkdirty(entry));
+ entry = maybe_mkwrite(pte_mkdirty(entry), vma);
}

ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
diff --git a/mm/mprotect.c b/mm/mprotect.c
index ab709023e9aa..ed26e675c423 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -135,7 +135,7 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
if (dirty_accountable && pte_dirty(ptent) &&
(pte_soft_dirty(ptent) ||
!(vma->vm_flags & VM_SOFTDIRTY))) {
- ptent = pte_mkwrite(ptent);
+ ptent = maybe_mkwrite(ptent, vma);
}
ptep_modify_prot_commit(vma, addr, pte, oldpte, ptent);
pages++;
--
2.21.0