[PATCH v4 10/14] mm/userfaultfd: Support COW PTE

Chih-En Lin
2023-02-07T03:54:39Z

If uffd fills the zeropage or installs to COW-ed PTE, break it first.

Signed-off-by: Chih-En Lin <shiyn.lin@gmail.com>
---
mm/userfaultfd.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 0499907b6f1a..3f66aa3eb54f 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -70,6 +70,9 @@ int mfill_atomic_install_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd,
struct inode *inode;
pgoff_t offset, max_off;

+ if (break_cow_pte(dst_vma, dst_pmd, dst_addr))
+ return -ENOMEM;
+
_dst_pte = mk_pte(page, dst_vma->vm_page_prot);
_dst_pte = pte_mkdirty(_dst_pte);
if (page_in_cache && !vm_shared)
@@ -229,6 +232,9 @@ static int mfill_zeropage_pte(struct mm_struct *dst_mm,
pgoff_t offset, max_off;
struct inode *inode;

+ if (break_cow_pte(dst_vma, dst_pmd, dst_addr))
+ return -ENOMEM;
+
_dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
dst_vma->vm_page_prot));
dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
--
2.34.1