From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6E1EC3B4E9E for ; Wed, 9 Sep 2026 06:58:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788937135; cv=none; b=gBAP6PdT/7WA8XCr29LNy/1jev9sa9shH946Ru0k4QxNqMifh2YOwGlfvDsyS0W1grNxRFbg5SdUmBR9S5WTNd/hM2om2wzo1rtw03brilgaYFunHlrCkVO7PiemR60o6J9fQpEgYHOi/hdl9YuQa56byj20aI5ZNLVGiFZvooQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788937135; c=relaxed/simple; bh=we4V3RFMUny7o4+1XQM6aF2fjqxZfTx6mi/PDj+Z0+k=; h=Date:To:From:Subject:Message-Id; b=fEVwZRrFwgr/c0RwUNLa83PrSXrfUF4P+hlbUjCoX0Vm0RD/TSYObZERrE7jMFkbexNLl8FZ4PHAPDRUcxNkRWD4uHtee3h+V9bR67KUENaCpNuBeQ1KnnZwxA2yravrAdrCR4ZF5Dcnp/NjtVf0CHY1oweAFSnszjFrFgMhTJs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=OmA8Drkr; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="OmA8Drkr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B0CCE1F00A3A; Wed, 9 Sep 2026 06:58:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1788937133; bh=oGVfUfQoFu09HQavq/q3f3k3tObWXuC8sKcke/arwhA=; h=Date:To:From:Subject; b=OmA8Drkrj+Jw2EKIY+fBVkIw2hAaJOBWvL6O5FK0jYrix/8aelnzH3kivslXQNqqC GpZk8ku5l9AZ156jNGsmMhsCOt7fHzCquVWbJkG8csjFCQ14tk5HaODRh4uKMl4BoN XZA0+DKeH4SN4cYyzDuBUDaeQABOHIXUPoV9Vj/Y= Date: Tue, 08 Sep 2026 23:58:53 -0700 To: mm-commits@vger.kernel.org,yanglincheng@kylinos.cn,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-khugepaged-fix-folio-is-used-after-pte_unmap_unlock.patch added to mm-unstable branch Message-Id: <20260909065853.B0CCE1F00A3A@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm: khugepaged: fix folio is used after pte_unmap_unlock() has been added to the -mm mm-unstable branch. Its filename is mm-khugepaged-fix-folio-is-used-after-pte_unmap_unlock.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-khugepaged-fix-folio-is-used-after-pte_unmap_unlock.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Vernon Yang Subject: mm: khugepaged: fix folio is used after pte_unmap_unlock() Date: Wed, 9 Sep 2026 10:58:02 +0800 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. And other pre-existing bug, When the `for (i = 0; i < HPAGE_PMD_NR; i++)` iteration to terminate and the folio operation preceding is normal, but pfn will be incorrect. so we really only trace the PFN if it really was problematic. Link: https://lore.kernel.org/20260909025804.3233645-3-vernon2gm@gmail.com Fixes: 7d2eba0557c1 ("mm: add tracepoint for scanning pages") Signed-off-by: Vernon Yang Acked-by: David Hildenbrand (Arm) Acked-by: Lorenzo Stoakes (ARM) Cc: Barry Song Cc: Dev Jain Cc: Lance Yang Cc: Ryan Roberts Cc: Zach O'Keefe Cc: Signed-off-by: Andrew Morton --- include/trace/events/huge_memory.h | 6 +++--- mm/khugepaged.c | 10 +++++++++- 2 files changed, 12 insertions(+), 4 deletions(-) --- a/include/trace/events/huge_memory.h~mm-khugepaged-fix-folio-is-used-after-pte_unmap_unlock +++ a/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; --- a/mm/khugepaged.c~mm-khugepaged-fix-folio-is-used-after-pte_unmap_unlock +++ a/mm/khugepaged.c @@ -1612,6 +1612,7 @@ static enum scan_result collapse_scan_pm enum scan_result result = SCAN_FAIL; struct page *page = NULL; struct folio *folio = NULL; + unsigned long failed_pfn = -1; unsigned long addr; unsigned long enabled_orders; spinlock_t *ptl; @@ -1706,11 +1707,13 @@ static enum scan_result collapse_scan_pm if (cc->is_khugepaged && !(vma->vm_flags & VM_DROPPABLE) && folio_test_lazyfree(folio) && !pte_dirty(pteval)) { result = SCAN_PAGE_LAZYFREE; + failed_pfn = folio_pfn(folio); goto out_unmap; } if (!folio_test_anon(folio)) { result = SCAN_PAGE_ANON; + failed_pfn = folio_pfn(folio); goto out_unmap; } @@ -1721,6 +1724,7 @@ static enum scan_result collapse_scan_pm if (folio_maybe_mapped_shared(folio)) { if (++shared > max_ptes_shared) { result = SCAN_EXCEED_SHARED_PTE; + failed_pfn = folio_pfn(folio); count_collapse_event(HPAGE_PMD_ORDER, THP_SCAN_EXCEED_SHARED_PTE, MTHP_STAT_COLLAPSE_EXCEED_SHARED); goto out_unmap; @@ -1738,15 +1742,18 @@ static enum scan_result collapse_scan_pm node = folio_nid(folio); if (collapse_scan_abort(node, cc)) { result = SCAN_SCAN_ABORT; + failed_pfn = folio_pfn(folio); goto out_unmap; } cc->node_load[node]++; if (!folio_test_lru(folio)) { result = SCAN_PAGE_LRU; + failed_pfn = folio_pfn(folio); goto out_unmap; } if (folio_test_locked(folio)) { result = SCAN_PAGE_LOCK; + failed_pfn = folio_pfn(folio); goto out_unmap; } @@ -1759,6 +1766,7 @@ static enum scan_result collapse_scan_pm */ if (folio_expected_ref_count(folio) != folio_ref_count(folio)) { result = SCAN_PAGE_COUNT; + failed_pfn = folio_pfn(folio); goto out_unmap; } @@ -1784,7 +1792,7 @@ out_unmap: *lock_dropped = true; } out: - trace_mm_khugepaged_scan_pmd(mm, folio, referenced, + trace_mm_khugepaged_scan_pmd(mm, failed_pfn, referenced, none_or_zero, result, unmapped); return result; } _ Patches currently in -mm which might be from yanglincheng@kylinos.cn are x86-mm-fix-pmd_modify-dropping-the-dirty-bit.patch mm-khugepaged-fix-swap-entry-value-to-folio_pfn.patch mm-khugepaged-fix-folio-is-used-after-pte_unmap_unlock.patch mm-khugepaged-fix-folio-is-used-after-folio_put-unlock.patch