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 A04472D7DD7; Tue, 13 Oct 2026 04:31:54 +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=1791865915; cv=none; b=MEndAi7DHwj4GBGyojz5+RabaAwO+R6I9OBe0mpLqdn2WpKjdyB7dTCmcxGfRLhe9gUDjCpgTSwSrkUHcVoCP8epIe06TgJJF3KK8nDgfW9lRFI9l69pIHfY5Zv8tGPremrHPMiT4yYv1fRtLnOSO8KdNbxSIuBAWXH2qVYfeGw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791865915; c=relaxed/simple; bh=ns6ef2NSBFmlJnaNVR0S74xT5Oojfn+O0Tybs2j7Brw=; h=Date:To:From:Subject:Message-Id; b=Tta1OaPtN82v1WPZifdEIdRer+2/Gs1pwuI46cY9JM5iAvwBKzKMx3jksn18THhgYfMzxaOZiTYtsFdiZOsJXljbXLveWKUqLDKe0LrDn0fJ0k9K0aHHbgA4yj/t8ouGpHztSKmD7hA1E/C8kjiotvtXs0Qak6EgTDCyqk0flH8= 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=VhYSQlml; 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="VhYSQlml" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 775E31F00893; Tue, 13 Oct 2026 04:31:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1791865914; bh=76ZQtbxO0VIM+bPanI+GsfDotLqkwS1YfhEQIPi5ic8=; h=Date:To:From:Subject; b=VhYSQlmlS3DhT6GdoQmW8X0KKnZfOnUa5eQX9rbQuMJ+SRck8Z33VfGDYfDwtKocM 21Um0DzESeNyn/oymvOQ0Y0bWiTiPnl/GZnNLHwkqcBKL8VTYH3IcuqMlx6VJgEq7R 8ZKR2uxF6x6bQnR2IW7WQkmOC1sp6Y3nlzbGfZUw= Date: Mon, 12 Oct 2026 21:31:54 -0700 To: mm-commits@vger.kernel.org,vbabka@kernel.org,stable@vger.kernel.org,sashiko-bot@kernel.org,pfalcato@suse.de,peterx@redhat.com,ljs@kernel.org,liam@infradead.org,jgg@ziepe.ca,jannh@google.com,david@kernel.org,gourry@gourry.net,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-stable] proc-task_mmu-handle-special-pmds-in-clear_refs-and-pagemap.patch removed from -mm tree Message-Id: <20261013043154.775E31F00893@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: proc/task_mmu: handle special PMDs in clear_refs and pagemap has been removed from the -mm tree. Its filename was proc-task_mmu-handle-special-pmds-in-clear_refs-and-pagemap.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: Gregory Price Subject: proc/task_mmu: handle special PMDs in clear_refs and pagemap Date: Sat, 12 Sep 2026 08:28:22 -0400 mshv_vtl_low can install a special PMD from a PFN supplied in the mmap file offset. That PFN need not have a memmap entry. Reading /proc/PID/pagemap or writing /proc/PID/clear_refs for such a mapping oopses the kernel. With a test driver mapping the PFN at the 1 TiB mark: echo 1 > /proc/self/clear_refs BUG: unable to handle page fault for address: fffffb5b80000008 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page RIP: 0010:clear_refs_pte_range+0xb1/0x1e0 Call Trace: walk_pgd_range+0x50a/0xad0 __walk_page_range+0x6a/0x1d0 walk_page_range_mm_unsafe+0x193/0x230 clear_refs_write+0x18e/0x3f0 pread(pagemap_fd, buf, 512 * 8, addr / PAGE_SIZE * 8) BUG: unable to handle page fault for address: fffff57840000008 RIP: 0010:pagemap_pmd_range+0x3cf/0x6b0 Call Trace: walk_pgd_range+0x50a/0xad0 __walk_page_range+0x6a/0x1d0 walk_page_range_mm_unsafe+0x193/0x230 pagemap_read+0x1dc/0x350 clear_refs_pte_range() passes the PMD to pmd_folio(), while pagemap_pmd_range_thp() uses pmd_page() followed by page_folio(). Both paths assume the PFN has a struct page and dereference bad address. Use vm_normal_folio_pmd() and vm_normal_page_pmd() so clear_refs skips folio operations and pagemap skips folio-derived flags for special PMDs. This matches the PTE paths, which already use vm_normal_folio() and vm_normal_page(). User-facing notes: - Pagemap still reports PM_PRESENT and the PFN to a CAP_SYS_ADMIN reader. - For a special PMD backed by a valid memmap entry and for the huge zero PMD, PM_FILE changes from set to clear. - PM_MMAP_EXCLUSIVE is already clear in both cases. - The output for an anonymous THP is unchanged. Tested in QEMU with the test driver on broken and fixed kernels. Both proc operations oops before the fix and return 0 after it. This is technically reachable via mshv_vtl_low, so I tagged it stable. Link: https://lore.kernel.org/20260912122822.3348978-1-gourry@gourry.net Fixes: 3c8e44c9b369 ("mm: mark special bits for huge pfn mappings when inject") Signed-off-by: Gregory Price Signed-off-by: Andrew Morton Reported-by: sashiko-bot Closes: https://sashiko.dev/#/patchset/20260912034833.2952750-1-gourry%40gourry.net Acked-by: David Hildenbrand (Arm) Assisted-by: LLM Cc: Jann Horn Cc: Jason Gunthorpe Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Pedro Falcato Cc: Peter Xu Cc: Vlastimil Babka Cc: # v6.19+ --- fs/proc/task_mmu.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/fs/proc/task_mmu.c~proc-task_mmu-handle-special-pmds-in-clear_refs-and-pagemap +++ a/fs/proc/task_mmu.c @@ -1704,7 +1704,9 @@ static int clear_refs_pte_range(pmd_t *p if (!pmd_present(*pmd)) goto out; - folio = pmd_folio(*pmd); + folio = vm_normal_folio_pmd(vma, addr, *pmd); + if (!folio) + goto out; /* Clear accessed and referenced bits. */ pmdp_test_and_clear_young(vma, addr, pmd); @@ -2024,7 +2026,7 @@ static int pagemap_pmd_range_thp(pmd_t * goto populate_pagemap; if (pmd_present(pmd)) { - page = pmd_page(pmd); + page = vm_normal_page_pmd(vma, addr, pmd); flags |= PM_PRESENT; if (pmd_soft_dirty(pmd)) _ Patches currently in -mm which might be from gourry@gourry.net are mm-damon-use-damon_get_monitor_folio-for-hugetlb-entries.patch