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@xxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
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 c8e357627318..0bdc6f2a8fe0 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3559,8 +3559,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
__SetPageUptodate(page);
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);
vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address,
&vmf->ptl);
@@ -4123,7 +4122,7 @@ 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 62b81d5257aa..7251c88a3d64 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2976,8 +2976,7 @@ 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 94188df1ee55..c1ce78d688b6 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
