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 45A162EFD95; Wed, 7 Oct 2026 00:49:58 +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=1791334200; cv=none; b=P6tCDggi6gC+5SBwP0Knndm2I8NXWrwJMEJLznAEiam0MArQWIQJUQEys48E17drLvV2vsCixm3tlrecQB/Y0jXFRQtYk5EP1UxBG8lxw3xMu81TAle/jkYzkXttEu+YHQEoKieAgamds6DPWCqDSdcHaJ2yfRp/YwY6KllAuAQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791334200; c=relaxed/simple; bh=H3DzCo9uhi9f80w/cV9chUvOC+IUwWDdPmpZCzy4ke8=; h=Date:To:From:Subject:Message-Id; b=Xr2k2ZWkK9sAHORXXod8jPLMTNzlcOFKio2xuHvyi+k5LFYXTcbhtPrKd65U52+9Ks+yPC2X0zqlahoRxQ7Vo51TZMX/u4ngeNeNhY1WhLcmFJ7yTS1pFvdQRaZluFWMvPXoc/a6bcZP6Q7GrRQodRQH5k5+2QqxFxQhvCC/kqk= 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=oZSOn0qD; 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="oZSOn0qD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CCA031F0089B; Wed, 7 Oct 2026 00:49:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1791334197; bh=sgGeHsLu/zTC6nKKn6Co9AtOtazoKFNgdmcgc71+sOw=; h=Date:To:From:Subject; b=oZSOn0qD99Pyfw2fYOGzhc7Saa/xZi+YwlUnwk1DjgxiF0Z8J+QIdtWekjljRVmIm 1gLxV17uvDIACHlKaqbXcA+NRGWBL/C0aelvUxf/wqqAdAVZo9ayv9/IjVG7S/uzRO zD2omPxYrgtftg2cXmdkAceHVawWaJL70LCtMCH0= Date: Tue, 06 Oct 2026 17:49:57 -0700 To: mm-commits@vger.kernel.org,zokeefe@google.com,stable@vger.kernel.org,ryan.roberts@arm.com,ljs@kernel.org,lance.yang@linux.dev,dev.jain@arm.com,david@kernel.org,baohua@kernel.org,yanglincheng@kylinos.cn,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-stable] mm-khugepaged-fix-swap-entry-value-to-folio_pfn.patch removed from -mm tree Message-Id: <20261007004957.CCA031F0089B@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm: khugepaged: fix swap entry value to folio_pfn() has been removed from the -mm tree. Its filename was mm-khugepaged-fix-swap-entry-value-to-folio_pfn.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Vernon Yang Subject: mm: khugepaged: fix swap entry value to folio_pfn() Date: Wed, 9 Sep 2026 10:58:01 +0800 Patch series "mm: khugepaged: fix tracepoint UAF", v5. The khugepaged tracepoints take a folio pointer and call folio_pfn(), but by then the folio may no longer be valid: freed after folio_put(), folio_unlock() or pte_unmap_unlock(), or not a folio at all but an xarray-encoded swap entry. On classic SPARSEMEM, dereferencing it oopses khugepaged as soon as the trace event is enabled; on other memory models it merely prints a bogus pfn. Pass the pfn to the tracepoints directly, captured while the folio is still pinned, closing the use-after-free windows in mm_khugepaged_scan_file(), mm_khugepaged_scan_pmd() and mm_khugepaged_collapse_file(). This patch (of 3): When the swap entries found exceed max_ptes_swap, the loop is left via break with folio still holding the xarray value that encodes the swap entry, not valid folio pointer. That value is passed to trace_mm_khugepaged_scan_file(), which feeds it to folio_pfn(). On FLATMEM and SPARSEMEM_VMEMMAP, the page_to_pfn() is plain pointer arithmetic, so the trace event merely prints bogus scan_pfn. On classic SPARSEMEM, the page_to_pfn() reads page->flags, dereferencing the tiny encoded integer and oopsing khugepaged whenever the trace event is enabled. So when folio is the swap entry value, simply set pfn to -1, just like exhausted scan naturally. And the folio_put() has maybe dropped the last reference of folio. The trace_mm_khugepaged_scan_file() is left with a dangling folio pointer. so using the folio_pfn() before dropping the reference, closing use-after-free window. Link: https://lore.kernel.org/20260909025804.3233645-1-vernon2gm@gmail.com Link: https://lore.kernel.org/20260909025804.3233645-2-vernon2gm@gmail.com Fixes: d41fd2016ed0 ("mm/khugepaged: add tracepoint to hpage_collapse_scan_file()") Signed-off-by: Vernon Yang Signed-off-by: Andrew Morton Acked-by: David Hildenbrand (Arm) Cc: Barry Song Cc: Dev Jain Cc: Lance Yang Cc: Lorenzo Stoakes Cc: Ryan Roberts Cc: Zach O'Keefe Cc: --- include/trace/events/huge_memory.h | 6 +++--- mm/khugepaged.c | 7 ++++++- 2 files changed, 9 insertions(+), 4 deletions(-) --- a/include/trace/events/huge_memory.h~mm-khugepaged-fix-swap-entry-value-to-folio_pfn +++ a/include/trace/events/huge_memory.h @@ -178,10 +178,10 @@ TRACE_EVENT(mm_collapse_huge_page_swapin TRACE_EVENT(mm_khugepaged_scan_file, - TP_PROTO(struct mm_struct *mm, struct folio *folio, struct file *file, + TP_PROTO(struct mm_struct *mm, unsigned long pfn, struct file *file, int present, int swap, int result), - TP_ARGS(mm, folio, file, present, swap, result), + TP_ARGS(mm, pfn, file, present, swap, result), TP_STRUCT__entry( __field(struct mm_struct *, mm) @@ -194,7 +194,7 @@ TRACE_EVENT(mm_khugepaged_scan_file, TP_fast_assign( __entry->mm = mm; - __entry->pfn = folio ? folio_pfn(folio) : -1; + __entry->pfn = pfn; __assign_str(filename); __entry->present = present; __entry->swap = swap; --- a/mm/khugepaged.c~mm-khugepaged-fix-swap-entry-value-to-folio_pfn +++ a/mm/khugepaged.c @@ -2683,6 +2683,7 @@ static enum scan_result collapse_scan_fi int present, swap; int node = NUMA_NO_NODE; enum scan_result result = SCAN_SUCCEED; + unsigned long failed_pfn = -1; present = 0; swap = 0; @@ -2715,6 +2716,7 @@ static enum scan_result collapse_scan_fi if (is_pmd_order(folio_order(folio))) { result = SCAN_PTE_MAPPED_HUGEPAGE; + failed_pfn = folio_pfn(folio); /* * PMD-sized THP implies that we can only try * retracting the PTE table. @@ -2726,6 +2728,7 @@ static enum scan_result collapse_scan_fi node = folio_nid(folio); if (collapse_scan_abort(node, cc)) { result = SCAN_SCAN_ABORT; + failed_pfn = folio_pfn(folio); folio_put(folio); break; } @@ -2733,12 +2736,14 @@ static enum scan_result collapse_scan_fi if (!folio_test_lru(folio)) { result = SCAN_PAGE_LRU; + failed_pfn = folio_pfn(folio); folio_put(folio); break; } if (folio_expected_ref_count(folio) + 1 != folio_ref_count(folio)) { result = SCAN_PAGE_COUNT; + failed_pfn = folio_pfn(folio); folio_put(folio); break; } @@ -2773,7 +2778,7 @@ static enum scan_result collapse_scan_fi } } - trace_mm_khugepaged_scan_file(mm, folio, file, present, swap, result); + trace_mm_khugepaged_scan_file(mm, failed_pfn, file, present, swap, result); return result; } _ Patches currently in -mm which might be from yanglincheng@kylinos.cn are