If the PTE table is COW-ed, break it before changing the protection.
Signed-off-by: Chih-En Lin <shiyn.lin@xxxxxxxxx>
---
mm/mprotect.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 13e84d8c0797..a33f23a73fa5 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -103,6 +103,9 @@ static long change_pte_range(struct mmu_gather *tlb,
if (pmd_trans_unstable(pmd))
return 0;
+ if (break_cow_pte(vma, pmd, addr))
+ return 0;
+
/*
* The pmd points to a regular pte so the pmd can't change
* from under us even if the mmap_lock is only hold for
@@ -312,6 +315,12 @@ static inline int pmd_none_or_clear_bad_unless_trans_huge(pmd_t *pmd)
return 1;
if (pmd_trans_huge(pmdval))
return 0;
+ /*
+ * If the entry point to COW-ed PTE, it's write protection bit
+ * will cause pmd_bad().
+ */
+ if (!pmd_write(pmdval))
+ return 0;
if (unlikely(pmd_bad(pmdval))) {
pmd_clear_bad(pmd);
return 1;
--
2.34.1
