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=1794047947; b=f4qLpdidiqXyraYkYGO63ha116SONaoImjBZirD99ms5dwwvTlUx5stQxNbKsGSVRckM REFN1tx2DNekgTuiKgEUTWYmC2fhja3MXAA+PUGXACoUqq6gzfcBmAJgEfK/gg6InTkMS rPKqZtTX8fl1liFPt4pI/ijtAdD06y31DTCCtbD317kK2pwrFOcldfbEMwXJJKYlbEqf/ 4B3ZITPcG3qGHm1Oq9PsKXwEKVkDp+1YzjZIdfVhuaw4+3vgrmRKON01eArKJdEfgoFjZ xGLkEAtvopUtjgvx30Fe5aJqnvHodFMWhV5a/tWz9lUIhtSQhx6sxuf+NqXYpUWOBGQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794047947; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=edcOzBz5HIEC4dPdZ39e81BKB7o8Cleq+69kdlhyvTo=; b=OK78arA4PQzH7s64KtgcPCrNZDN/oNpXIRpkjdbPVy19Vj4sDAo/qeub+V0nnQYQR4De UtOPZ9bcvszLvaIrAdu9zIlPPRX7JMX4c3QmXvwpRO8faDvskJGsnBywggDIpB4c71xoh pM9/WKmyaKXk1uvKWMZ0xgxZ7TkfFMOKJYIcdWJCmPXC7PLM3PCKcFI9+Nt+QqEmevd53 whzNl7XhlQ0GlcD4rvl7sLL0nxrDaYC6uzONOD1EEh8U5pMZdAdzEwd+SXpe/GO5+QO9g +BT2tQsxIvzQzLrdGvm6G+ak9uLReqiVOnWedoKNtrSO6m192qmWdoLHzFufvy0QC3w== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=MfswgZR3; 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 620F7606A32C for ; Sat, 7 Nov 2026 10:39:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=MfswgZR3 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1E8E51F0089F; Sat, 7 Nov 2026 10:39:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794047947; bh=edcOzBz5HIEC4dPdZ39e81BKB7o8Cleq+69kdlhyvTo=; h=From:To:Cc:Subject:Date; b=MfswgZR3+hUK6NhuwTGrfSGw5QrTdR0d6paBSrb2u3O8MO9le3CKA+r2OxtuuS7QL T45vYBWYgFLnk3h3Mr4Fb6eU/L8FCssNqE93aK9KG6KrgG0b9jgEqCi/p/wVKxnqLP 3USVMbJp0V9gh7EHKaxmbQp3psvH6lMCgjqUKw7ZxZw6VQpe5y9Rolc2bAkb4hgT5N jgy9C9YE7jqmoUwj/eeKZ9q6OkKq2Sl2/DZrQO48F73cQbrFvrOAVjDLxEpbWThZwg 5lehhzTK/q+2e19jzyPt19cBjuEGgkYcwl2TGshWPfKu/DX7Eq58RftuiklaIdYVQT M3tbrEmkrtD8g== From: Sasha Levin To: kylebot@openai.com, akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, riel@surriel.com, liam@infradead.org, vbabka@kernel.org, harry@kernel.org, jannh@google.com, lance.yang@linux.dev Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] mm/page_vma_mapped: continue past nonmatching huge PMDs" failed to apply to 6.6-stable tree Date: Sat, 7 Nov 2026 05:39:05 -0500 Message-ID: <20261107053904-failed-6.6-1a2993227e8a@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 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 1a2993227e8a27fc4cdea305bbdae82d290bc885 # git commit -s git send-email --to '' --in-reply-to '20261107053904-failed-6.6-1a2993227e8a@kernel.org' --subject-prefix 'PATCH 6.6.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From 1a2993227e8a27fc4cdea305bbdae82d290bc885 Mon Sep 17 00:00:00 2001 From: Kyle Zeng Date: Thu, 15 Oct 2026 18:15:49 -0700 Subject: [PATCH] mm/page_vma_mapped: continue past nonmatching huge PMDs A PTE-mapped large folio can straddle PMD boundaries after an unaligned mremap(). If the first part is discarded and replaced with an unrelated huge PMD, page_vma_mapped_walk() stops instead of looking for the rest of the folio in subsequent PMDs. This also affects migration entries. A walk that stops at an unrelated huge PMD can leave migration PTEs behind when migration or an anonymous folio split restores the mappings. Those entries do not hold mapping references and can outlive the source folio. This issue can lead to memory corruption and I have a reproducer for it. Skip the current PMD rather than ending the walk on a flag or PFN mismatch. Do the same if the PMD became nonpresent before the locked recheck. Release the PMD lock, clear the per-PMD state and advance with step_forward(), so the existing range limit controls termination. This covers present, migration and device-private huge PMDs while preserving the matching-PMD and split-to-PTE paths. Link: https://lore.kernel.org/20261016011549.61146-1-kylebot@openai.com Fixes: ace71a19cec5 ("mm: introduce page_vma_mapped_walk()") Signed-off-by: Kyle Zeng Signed-off-by: Andrew Morton Acked-by: David Hildenbrand (Arm) Assisted-by: LLM Cc: Lorenzo Stoakes Cc: Rik van Riel Cc: Liam R. Howlett Cc: Vlastimil Babka Cc: Harry Yoo Cc: Jann Horn Cc: Lance Yang Cc: --- mm/page_vma_mapped.c | 28 +++++++++++++++++++--------- 1 file changed, 19 insertions(+), 9 deletions(-) diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c index 8408aee7571b5..e6b6170c2f4f7 100644 --- a/mm/page_vma_mapped.c +++ b/mm/page_vma_mapped.c @@ -265,28 +265,28 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) softleaf_t entry; if (!(pvmw->flags & PVMW_MIGRATION)) - return not_found(pvmw); + goto next_pmd; entry = softleaf_from_pmd(pmde); if (!check_pmd(softleaf_to_pfn(entry), pvmw)) - return not_found(pvmw); + goto next_pmd; return true; } else if (pmd_is_device_private_entry(pmde)) { softleaf_t entry; if (pvmw->flags & PVMW_MIGRATION) - return not_found(pvmw); + goto next_pmd; entry = softleaf_from_pmd(pmde); if (!check_pmd(softleaf_to_pfn(entry), pvmw)) - return not_found(pvmw); + goto next_pmd; return true; } else if (!pmd_present(pmde)) { - return not_found(pvmw); + goto next_pmd; } if (likely(pmd_trans_huge(pmde))) { if (pvmw->flags & PVMW_MIGRATION) - return not_found(pvmw); + goto next_pmd; if (!check_pmd(pmd_pfn(pmde), pvmw)) - return not_found(pvmw); + goto next_pmd; return true; } /* THP/device-private pmd was split under us: handle on pte level */ @@ -299,8 +299,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) (pvmw->nr_pages >= HPAGE_PMD_NR)) sync_with_folio_pmd_zap(mm, pvmw->pmd); - step_forward(pvmw, PMD_SIZE); - continue; + goto next_pmd; } if (!map_pte(pvmw, &pmde, &ptl)) { if (!pvmw->pte) @@ -343,6 +342,17 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) pvmw->ptl = ptl; } goto this_pte; +next_pmd: + /* + * A large folio can be PTE-mapped across PMDs, so a + * nonmatching PMD does not end the walk. + */ + if (pvmw->ptl) { + spin_unlock(pvmw->ptl); + pvmw->ptl = NULL; + } + pvmw->pmd = NULL; + step_forward(pvmw, PMD_SIZE); } while (pvmw->address < end); return false; -- 2.53.0