[PATCH] mm: hwposion: support recovery from ksm_might_need_to_copy()

[Kefeng Wang]

When the kernel copy a page from ksm_might_need_to_copy(), but runs
into an uncorrectable error, it will crash since poisoned page is
consumed by kernel, this is similar to Copy-on-write poison recovery,
When an error is detected during the page copy, return VM_FAULT_HWPOISON,
which help us to avoid system crash. Note, memory failure on a KSM
page will be skipped, but still call memory_failure_queue() to be
consistent with general memory failure process.

Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
---
 mm/ksm.c      | 8 ++++++--
 mm/memory.c   | 3 +++
 mm/swapfile.c | 2 +-
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/mm/ksm.c b/mm/ksm.c
index f1e06b1d47f3..356e93b85287 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2629,8 +2629,12 @@ struct page *ksm_might_need_to_copy(struct page *page,
 		new_page = NULL;
 	}
 	if (new_page) {
-		copy_user_highpage(new_page, page, address, vma);
-
+		if (copy_mc_user_highpage(new_page, page, address, vma)) {
+			put_page(new_page);
+			new_page = ERR_PTR(-EHWPOISON);
+			memory_failure_queue(page_to_pfn(page), 0);
+			return new_page;
+		}
 		SetPageDirty(new_page);
 		__SetPageUptodate(new_page);
 		__SetPageLocked(new_page);
diff --git a/mm/memory.c b/mm/memory.c
index 2615fa615be4..bb7b35e42297 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3840,6 +3840,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 		if (unlikely(!page)) {
 			ret = VM_FAULT_OOM;
 			goto out_page;
+		} els if (unlikely(PTR_ERR(page) == -EHWPOISON)) {
+			ret = VM_FAULT_HWPOISON;
+			goto out_page;
 		}
 		folio = page_folio(page);
 
diff --git a/mm/swapfile.c b/mm/swapfile.c
index f670ffb7df7e..763ff6a8a576 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1767,7 +1767,7 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
 
 	swapcache = page;
 	page = ksm_might_need_to_copy(page, vma, addr);
-	if (unlikely(!page))
+	if (IS_ERR_OR_NULL(!page))
 		return -ENOMEM;
 
 	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
-- 
2.35.3