If a VMA has the VM_SHADOW_STACK flag, it is shadow stack memory. So
when it is made writable with pte_mkwrite(), it should create shadow
stack memory, not conventionally writable memory. Now that all the places
where shadow stack memory might be created pass a VMA into pte_mkwrite(),
it can know when it should do this.
So make pte_mkwrite() create shadow stack memory when the VMA has the
VM_SHADOW_STACK flag. Do the same thing for pmd_mkwrite().
This requires referencing VM_SHADOW_STACK in these functions, which are
currently defined in pgtable.h, however mm.h (where VM_SHADOW_STACK is
located) can't be pulled in without causing problems for files that
reference pgtable.h. So also move pte/pmd_mkwrite() into pgtable.c, where
they can safely reference VM_SHADOW_STACK.
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
Reviewed-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Acked-by: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
Acked-by: Deepak Gupta <debug@xxxxxxxxxxxx>
Tested-by: Pengfei Xu <pengfei.xu@xxxxxxxxx>
Tested-by: John Allen <john.allen@xxxxxxx>
Tested-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
arch/x86/mm/pgtable.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 101e721d74aa..c4b222d3b1b4 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -883,6 +883,9 @@ int pmd_free_pte_page(pmd_t *pmd, unsigned long addr)
pte_t pte_mkwrite(pte_t pte, struct vm_area_struct *vma)
{
+ if (vma->vm_flags & VM_SHADOW_STACK)
+ return pte_mkwrite_shstk(pte);
+
pte = pte_mkwrite_novma(pte);
return pte_clear_saveddirty(pte);
@@ -890,6 +893,9 @@ pte_t pte_mkwrite(pte_t pte, struct vm_area_struct *vma)
pmd_t pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
{
+ if (vma->vm_flags & VM_SHADOW_STACK)
+ return pmd_mkwrite_shstk(pmd);
+
pmd = pmd_mkwrite_novma(pmd);
return pmd_clear_saveddirty(pmd);
--
2.34.1
