From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793827171; b=pVYB6fJWPcqrZe1y/T3KwkmVKt15J2bILa7hlGFqLtX4GqfuVwV7aUNxfU7iBnhS1RIs JadKqqNOamOD/0KG7V0KptFchfdJpKSmh7z/UwroQdDMRoW753KwWfYjTSmEFOgFxvTR9 i9jDBfBknpYCot4Ixwl3v/O5IL+3Gog6FmQRTZ4h4kC743ngtGbudv1aRNfAzh3W+Ym70 GwWZF8QsHKSu9JBaA+lwhveghx9Iwv6j8Ptrw+j9Lc3JScBCyG5SnRD8/WPmV460CJt2J ZJnBnQkuEUPsq+2I97u0PTEdcE4CIMK0/vEXzguChxJlEDazogNwnWnKuO4zFEoXvAg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793827171; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=KO1+z1UxH7Givjc/mFZKfoPP8t84ziOk5LLcEek4BNA=; b=wT4sZT/hrCU3FI+0crE2khZ5Ur/9zP7M03wa3N3N6dIXpsyHjQpBjeqRTTCkw1A+xx+R A6y8X8+xircpTW0ga2BTMglP8JjZsVAxV7CKgelKgCxVP0g3tiQaWjG0cIlw8yTqgUrlR 6pfrmmmZbnRNQLk8TVsORD1+CnXwsEfGO0vqEqUfSjLrhzbzXBcMKdofsPAUzvRuyAoTG 27V6i3CkTKogbfOaX/ADArp8Hkw+xESCHb6td+ExGqWEi9FwkFuBpN57Bp3y3Jk/ejy1J bIlggT6bYT8SBfN1iUj50IO83fckHu0+LX2AivpKzm/+IPdGwZzQ3uls2TcW2H9muhQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=S39Jd521; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0CA826074FB4; Wed, 4 Nov 2026 21:19:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=S39Jd521 Received: by smtp.kernel.org (Postfix) with ESMTPSA id B29D01F00A20; Wed, 4 Nov 2026 21:19:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793827171; bh=KO1+z1UxH7Givjc/mFZKfoPP8t84ziOk5LLcEek4BNA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=S39Jd521jYTHdqvCwHn79qJ6RCfZ03rPYqQKJgIznodrap3h/ySrvF38iutXv/lwQ FFOVgrsKAjQX26Z1gcnZmzACpb/cZqY4GDE2P9pK1tsS2PalwWUjuIKTwePf6rXI+J IJlE1M4gjLWB0NqySIYbkhjbDhvkQa0ZwpL+2Dxs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Vernon Yang , Andrew Morton , "David Hildenbrand (Arm)" , "Lorenzo Stoakes (ARM)" , Barry Song , Dev Jain , Lance Yang , Ryan Roberts , Zach OKeefe Subject: [PATCH 7.3 237/547] mm: khugepaged: fix folio is used after pte_unmap_unlock() Date: Wed, 4 Nov 2026 16:07:01 -0500 Message-ID: <20261104211044.897383673@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261104211038.406938024@linuxfoundation.org> References: <20261104211038.406938024@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vernon Yang commit ba2f1f92ddfabd340c9248fd2380104f717ee8b1 upstream. 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 Signed-off-by: Andrew Morton 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: Greg Kroah-Hartman --- 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 +++ 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; --- a/mm/khugepaged.c +++ b/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; }