[PATCH v2] mm/memory-failure: teach kill_accessing_process to accept hugetlb tail page pfn

[Jane Chu <jane.chu@oracle.com>]

When a hugetlb folio is being poisoned again, try_memory_failure_hugetlb()
passed head pfn to kill_accessing_process(), that is not right.
The precise pfn of the poisoned page should be used in order to
determine the precise vaddr as the SIGBUS payload.

This issue has already been taken care of in the normal path, that is,
hwpoison_user_mappings(), see [1][2].  Further more, for [3] to work
correctly in the hugetlb repoisoning case, it's essential to inform
VM the precise poisoned page, not the head page.

[1] https://lkml.kernel.org/r/20231218135837.3310403-1-willy@infradead.org
[2] https://lkml.kernel.org/r/20250224211445.2663312-1-jane.chu@oracle.com
[3] https://lore.kernel.org/lkml/20251116013223.1557158-1-jiaqiyan@google.com/

Cc: <stable@vger.kernel.org>
Signed-off-by: Jane Chu <jane.chu@oracle.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
---
v1 -> v2:
  pickup R-B, add stable to cc list.
---
 mm/memory-failure.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 3edebb0cda30..c9d87811b1ea 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -681,9 +681,11 @@ static void set_to_kill(struct to_kill *tk, unsigned long addr, short shift)
 }
 
 static int check_hwpoisoned_entry(pte_t pte, unsigned long addr, short shift,
-				unsigned long poisoned_pfn, struct to_kill *tk)
+				unsigned long poisoned_pfn, struct to_kill *tk,
+				int pte_nr)
 {
 	unsigned long pfn = 0;
+	unsigned long hwpoison_vaddr;
 
 	if (pte_present(pte)) {
 		pfn = pte_pfn(pte);
@@ -694,10 +696,11 @@ static int check_hwpoisoned_entry(pte_t pte, unsigned long addr, short shift,
 			pfn = swp_offset_pfn(swp);
 	}
 
-	if (!pfn || pfn != poisoned_pfn)
+	if (!pfn || (pfn > poisoned_pfn || (pfn + pte_nr - 1) < poisoned_pfn))
 		return 0;
 
-	set_to_kill(tk, addr, shift);
+	hwpoison_vaddr = addr + ((poisoned_pfn - pfn) << PAGE_SHIFT);
+	set_to_kill(tk, hwpoison_vaddr, shift);
 	return 1;
 }
 
@@ -749,7 +752,7 @@ static int hwpoison_pte_range(pmd_t *pmdp, unsigned long addr,
 
 	for (; addr != end; ptep++, addr += PAGE_SIZE) {
 		ret = check_hwpoisoned_entry(ptep_get(ptep), addr, PAGE_SHIFT,
-					     hwp->pfn, &hwp->tk);
+					     hwp->pfn, &hwp->tk, 1);
 		if (ret == 1)
 			break;
 	}
@@ -772,8 +775,8 @@ static int hwpoison_hugetlb_range(pte_t *ptep, unsigned long hmask,
 
 	ptl = huge_pte_lock(h, walk->mm, ptep);
 	pte = huge_ptep_get(walk->mm, addr, ptep);
-	ret = check_hwpoisoned_entry(pte, addr, huge_page_shift(h),
-					hwp->pfn, &hwp->tk);
+	ret = check_hwpoisoned_entry(pte, addr, huge_page_shift(h), hwp->pfn,
+				&hwp->tk, pages_per_huge_page(h));
 	spin_unlock(ptl);
 	return ret;
 }
@@ -2023,10 +2026,8 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
 		*hugetlb = 0;
 		return 0;
 	} else if (res == -EHWPOISON) {
-		if (flags & MF_ACTION_REQUIRED) {
-			folio = page_folio(p);
-			res = kill_accessing_process(current, folio_pfn(folio), flags);
-		}
+		if (flags & MF_ACTION_REQUIRED)
+			res = kill_accessing_process(current, pfn, flags);
 		action_result(pfn, MF_MSG_ALREADY_POISONED, MF_FAILED);
 		return res;
 	} else if (res == -EBUSY) {
@@ -2037,6 +2038,7 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
 		return action_result(pfn, MF_MSG_GET_HWPOISON, MF_IGNORED);
 	}
 
+
 	folio = page_folio(p);
 	folio_lock(folio);
 
-- 
2.43.5