[PATCH v3 2/3] mm: khugepaged: fix folio is used after pte_unmap_unlock()
Vernon Yang <[email protected]>
| Newsgroups | org.kvack.linux-mm,org.kernel.vger.linux-kernel,org.kernel.vger.stable |
|---|---|
| Message-ID | <[email protected]> |
From: Vernon Yang <[email protected]> After the page table lock has dropped, the folio can be freed concurrently. The trace_mm_khugepaged_scan_pmd() is left with a dangling folio pointer. So using the folio_pfn() before dropping the page table lock, closing use-after-free window. Fixes: 7d2eba0557c1 ("mm: add tracepoint for scanning pages") Cc: [email protected] Signed-off-by: Vernon Yang <[email protected]> --- include/trace/events/huge_memory.h | 6 +++--- mm/khugepaged.c | 5 ++++- 2 files changed, 7 insertions(+), 4 deletions(-) diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h index 7b526528f85b..fa828967e1fb 100644 --- a/include/trace/events/huge_memory.h +++ b/include/trace/events/huge_memory.h @@ -55,10 +55,10 @@ SCAN_STATUS TRACE_EVENT(mm_khugepaged_scan_pmd, - TP_PROTO(struct mm_struct *mm, struct folio *folio, + TP_PROTO(struct mm_struct *mm, unsigned long pfn, int referenced, int none_or_zero, int status, int unmapped), - TP_ARGS(mm, folio, referenced, none_or_zero, status, unmapped), + TP_ARGS(mm, pfn, referenced, none_or_zero, status, unmapped), TP_STRUCT__entry( __field(struct mm_struct *, mm) @@ -71,7 +71,7 @@ TRACE_EVENT(mm_khugepaged_scan_pmd, TP_fast_assign( __entry->mm = mm; - __entry->pfn = folio ? folio_pfn(folio) : -1; + __entry->pfn = pfn; __entry->referenced = referenced; __entry->none_or_zero = none_or_zero; __entry->status = status; diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 00337405c0e0..4e0fca5942dd 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1618,6 +1618,7 @@ static enum scan_result collapse_scan_pmd(struct mm_struct *mm, enum scan_result result = SCAN_FAIL; struct page *page = NULL; struct folio *folio = NULL; + unsigned long pfn = -1; unsigned long addr; unsigned long enabled_orders; spinlock_t *ptl; @@ -1780,6 +1781,8 @@ static enum scan_result collapse_scan_pmd(struct mm_struct *mm, result = SCAN_SUCCEED; } out_unmap: + if (folio) + pfn = folio_pfn(folio); pte_unmap_unlock(pte, ptl); if (result == SCAN_SUCCEED) { /* collapse_huge_page() expects the lock to be dropped before calling */ @@ -1790,7 +1793,7 @@ static enum scan_result collapse_scan_pmd(struct mm_struct *mm, *lock_dropped = true; } out: - trace_mm_khugepaged_scan_pmd(mm, folio, referenced, + trace_mm_khugepaged_scan_pmd(mm, pfn, referenced, none_or_zero, result, unmapped); return result; } -- 2.53.0