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 E372E3FADEE for ; Wed, 5 Aug 2026 09:33:32 +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=1785922416; cv=none; b=TbmgVy1YK/POBTxH3V1b2cpny46eNmpyFEHKHsFSHSjK6JYJNUKO+ftw+nxSPwrx93PivBgbh/wDSDBYTFZObBVMu9P1zABuvN+casK3IyRNr6mictJ/cmcomrbO8p00A5u9gx7Qr9KDsTYNFLqmXoBEbflOSvrOvvL7nSORIzM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785922416; c=relaxed/simple; bh=Kqymr7CNih/567YvlKgByUCsaD/2civHJj689IViI9g=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=mYf1sN+JJb9NUpMxrEksBgONR7Za27CP7nABx/ucyRyqBZB3K9kgaGj8uGmnAyvG4+tX3cVcmLJ3XYZfa84gUXDLCu5wVfHUfx4lGCMPTsFsPA9/S/s/gtMHDml2dBlxv0CwNVEKlHAQ+NuOoCFUGS1dNLe5MWdV2Cigf98JXpQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=T4kSLon4; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="T4kSLon4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4C1C51F000E9; Wed, 5 Aug 2026 09:33:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1785922410; bh=UnQhV2QEcA1pIfBrOfa3HcH++/NFdROwzr4gyRgdXL4=; h=Subject:To:Cc:From:Date; b=T4kSLon4OfrmdPm174aqcksb4AbjQV0r2LYsm6KVf2jXrT68dwfzXBCu/NNjZuKNI fFX+ou9pagyKBataRzK4kEgPPXilAIrs90o2NysXOf8hryXas7V7wrhxkOLCvrZv/T y5miHUSq6J/3XrGyrZsW0yFy/CZa8FLJoFU2J15U= Subject: FAILED: patch "[PATCH] fs/proc/task_mmu: fix PAGEMAP_SCAN written state for PMD" failed to apply to 6.6-stable tree To: kas@kernel.org,akpm@linux-foundation.org,david@kernel.org,jannh@google.com,liam@infradead.org,ljs@kernel.org,mhocko@suse.com,peterx@redhat.com,pfalcato@suse.de,rppt@kernel.org,sashiko-bot@kernel.org,shuah@kernel.org,stable@vger.kernel.org,surenb@google.com,usama.anjum@arm.com,vbabka@kernel.org,zenghui.yu@linux.dev Cc: From: Date: Wed, 05 Aug 2026 11:33:14 +0200 Message-ID: <2026080513-ambitious-sage-b240@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 40de8160ca7f67d14619ee0351ce5d68fc4a237a # git commit -s git send-email --to '' --in-reply-to '2026080513-ambitious-sage-b240@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 40de8160ca7f67d14619ee0351ce5d68fc4a237a Mon Sep 17 00:00:00 2001 From: "Kiryl Shutsemau (Meta)" Date: Wed, 15 Jul 2026 15:42:33 +0100 Subject: [PATCH] fs/proc/task_mmu: fix PAGEMAP_SCAN written state for PMD holes PAGEMAP_SCAN reports an unpopulated PTE in a uffd-wp VMA as written, but a range with no page table at all -- a PMD hole -- is skipped: pagemap_scan_pte_hole() tests p->cur_vma_category, which never carries PAGE_IS_WRITTEN, so the hole is neither reported nor (under PM_SCAN_WP_MATCHING) armed. In a uffd-wp VMA, WP_UNPOPULATED installs uffd-wp markers when protecting a range, allocating page tables as needed, so an unpopulated slot is treated as written -- see the pte_none() handling in pagemap_page_category(). A missing marker therefore means the range was zapped, e.g. via MADV_DONTNEED. This applies to anon and shmem VMAs. An anonymous THP is write-protected in place as a huge PMD, so a full-PMD MADV_DONTNEED clears it to pmd_none -- a hole with no page table -- and pagemap_scan_pte_hole() misses it. For a MAP_PRIVATE|MAP_ANON mapping MADV_DONTNEED has fill-with-zeros semantics, so a write-tracking checkpoint/migration tool (e.g. CRIU) treats the range as unchanged and keeps its previous contents; after restore or live migration the process reads stale data instead of zeroes -- data corruption. Report a hole in a non-hugetlb uffd-wp VMA as written, matching the pte_none handling in pagemap_page_category(); the existing PM_SCAN_WP_MATCHING path then arms it via uffd_wp_range(). hugetlb is excluded: pagemap_hugetlb_category() reports an empty hugetlb entry (huge_pte_none) as not-written, unlike pagemap_page_category(), which reports pte_none as written. pagemap_scan_pte_hole() fires for a hugetlb slot only when it has no page table; keeping that not-written matches how an allocated-but-empty hugetlb entry reads, so the hole and the empty-entry cases agree within the VMA. Link: https://lore.kernel.org/20260715144234.442721-2-kirill@shutemov.name Fixes: 2bad466cc9d9 ("mm/uffd: UFFD_FEATURE_WP_UNPOPULATED") Signed-off-by: Kiryl Shutsemau Reported-by: Sashiko AI review Closes: https://sashiko.dev/#/patchset/20260707151349.92143-1-kirill@shutemov.name Tested-by: Muhammad Usama Anjum Acked-by: David Hildenbrand (Arm) Cc: Peter Xu Cc: Jann Horn Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Pedro Falcato Cc: Shuah Khan Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Zenghui Yu Assisted-by: Claude:claude-fable-5 Cc: Signed-off-by: Andrew Morton diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index d45c729ab6bb..229d1fc3d7f1 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -3049,12 +3049,28 @@ static int pagemap_scan_pte_hole(unsigned long addr, unsigned long end, { struct pagemap_scan_private *p = walk->private; struct vm_area_struct *vma = walk->vma; + unsigned long categories; int ret, err; - if (!vma || !pagemap_scan_is_interesting_page(p->cur_vma_category, p)) + if (!vma) return 0; - ret = pagemap_scan_output(p->cur_vma_category, p, addr, &end); + /* + * In a uffd-wp VMA an unpopulated range is treated as written: + * uffd-wp registration populates page tables and installs markers + * with WP_UNPOPULATED, so a missing marker means the range was + * zapped. See the pte_none() handling in pagemap_page_category(). + * + * hugetlb differs, see pagemap_hugetlb_category(). + */ + categories = p->cur_vma_category; + if (userfaultfd_wp(vma) && !is_vm_hugetlb_page(vma)) + categories |= PAGE_IS_WRITTEN; + + if (!pagemap_scan_is_interesting_page(categories, p)) + return 0; + + ret = pagemap_scan_output(categories, p, addr, &end); if (addr == end) return ret;