mm/swapfile: fix wrong swap entry type for hwpoisoned swapcache page

Patch series "A few fixup patches for mm", v2. This series contains a few fixup patches to fix potential unexpected return value, fix wrong swap entry type for hwpoisoned swapcache page and so on. More details can be found in the respective changelogs. This patch (of 3): Hwpoisoned dirty swap cache page is kept in the swap cache and there's simple interception code in do_swap_page() to catch it. But when trying to swapoff, unuse_pte() will wrongly install a general sense of "future accesses are invalid" swap entry for hwpoisoned swap cache page due to unaware of such type of page. The user will receive SIGBUS signal without expected BUS_MCEERR_AR payload. BTW, typo 'hwposioned' is fixed. Link: https://lkml.kernel.org/r/[email protected] Link: https://lkml.kernel.org/r/[email protected] Fixes: 6b97059 ("mm: hwpoison: support recovery from ksm_might_need_to_copy()") Signed-off-by: Miaohe Lin <[email protected]> Cc: Kefeng Wang <[email protected]> Cc: Matthew Wilcox (Oracle) <[email protected]> Cc: Naoya Horiguchi <[email protected]> Cc: <[email protected]> Signed-off-by: Andrew Morton <[email protected]>
torvalds · Aug 4, 2023 · f985fc3 · f985fc3
1 parent cac7ea5
commit f985fc3
Show file tree

Hide file tree

Showing 2 changed files with 6 additions and 4 deletions.
diff --git a/mm/ksm.c b/mm/ksm.c
@@ -2784,6 +2784,8 @@ struct page *ksm_might_need_to_copy(struct page *page,
  anon_vma->root == vma->anon_vma->root) {
  return page; /* still no need to copy it */
  }
+ if (PageHWPoison(page))
+ return ERR_PTR(-EHWPOISON);
  if (!PageUptodate(page))
  return page; /* let do_swap_page report the error */
 

diff --git a/mm/swapfile.c b/mm/swapfile.c
@@ -1746,15 +1746,15 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
  struct page *swapcache;
  spinlock_t *ptl;
  pte_t *pte, new_pte, old_pte;
- bool hwposioned = false;
+ bool hwpoisoned = PageHWPoison(page);
  int ret = 1;
 
  swapcache = page;
  page = ksm_might_need_to_copy(page, vma, addr);
  if (unlikely(!page))
  return -ENOMEM;
  else if (unlikely(PTR_ERR(page) == -EHWPOISON))
- hwposioned = true;
+ hwpoisoned = true;
 
  pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
  if (unlikely(!pte || !pte_same_as_swp(ptep_get(pte),
@@ -1765,11 +1765,11 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
 
  old_pte = ptep_get(pte);
 
- if (unlikely(hwposioned || !PageUptodate(page))) {
+ if (unlikely(hwpoisoned || !PageUptodate(page))) {
  swp_entry_t swp_entry;
 
  dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
- if (hwposioned) {
+ if (hwpoisoned) {
  swp_entry = make_hwpoison_entry(swapcache);
  page = swapcache;
  } else {