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=1794046475; b=1t3Jm+TutX9yAkxLDFwBmliWnQCZZoAHR/89EfQS0qcZ28ZBdVvK6wFGThic2cd83kf4 ztX16TSkdpjTCscnbDH5kSXVupc1LjALHV3DFgdTeOhKza/zOvo+5UK240qFrTNWhN0D0 m4T46c93ojJy2FtxmvmfeM+7ZJUuV15+U924vhzqg8EcgdrNaNlDyF+59fsZPU6aNKSEy ik9p5JGZ/wuTXtFL+STAkdVqFt6E9wuYScSeQqLKF9sB+qqRUc01Idj3Mm8dwinxN/JI2 ciyF248dFJKL5GRzZiaW9AdMnzbINvK0m2C+VBcsN9FfZWssbt9bAQ8LJsEnPu4fb3A== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794046475; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=fqJLbSiPYa2/frIvhi77KplRibXyt8k4ekG10Zgoa6c=; b=FvyTdjcbpNwnZsI9vs4+p6GypmcXEJSlgRjN5VpKyepPuxt0enY1dCc1SfQeKR45mnGD cZJtzYC9zOPNi1hW8VeYz6izCL8OCrQ8lUwg/wyABgWTN126Q4uexWV2OknwiNM0FukzP FEUy31D0aa2hu9cCcGuWTnxPB5LwZIBYaXuaHuYLrygew6LT+XYpKB++aE612ojlW6KRX 4lbQpu7RIa5xNLlMDaDj3Zwm1AW2b+TzjpXV0HI/Yw59zd20r8kCqW+KxqkFp1iQTf01g 6/Qbr6HpKuYAiOPIX6WrzPsQEOT5QgdGulcSQoAVqV6MPiWRuADIAa2VDjVY05Yq0/A== 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=YNPbXBQV; 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 52EE8606A326 for ; Sat, 7 Nov 2026 10:14:35 +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=YNPbXBQV Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1E9091F0089F; Sat, 7 Nov 2026 10:14:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794046475; bh=fqJLbSiPYa2/frIvhi77KplRibXyt8k4ekG10Zgoa6c=; h=From:To:Cc:Subject:Date; b=YNPbXBQV6OR1UIZGzsZUfQ+8yW6Nfhf9/2zif3iH8hvIUMDApMzuyesLlEA1bYx+b aE8WYDFbtOt/6QF+Lof9qVBuchfInV9OxIzYZXnZmjown1syil80XWjARFkr24SMZe 9Y/X3TNmkohSRBXwhp5bhhdDyL+/3XzuBi2Yq63lDVa4byajMzhe2kKbOlCa6hpalb CiIUUBP5wURQA78PJ1LJ6kGHvBuWG/wgo/VUNMjODT7wsJTucTylso6n98VldgjxjR XiseDtigeFVHbvAbaLF6zMz15Pripag3zZAG6xsd9f2LC2ctCDscxy4RnfvffxwBUX bVYSn3NEoeMrQ== 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 6.18-stable tree Date: Sat, 7 Nov 2026 05:14:33 -0500 Message-ID: <20261107051433-failed-6.18-1a2993227e8a@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 6.18-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-6.18.y git checkout FETCH_HEAD git cherry-pick -x 1a2993227e8a27fc4cdea305bbdae82d290bc885 # git commit -s git send-email --to '' --in-reply-to '20261107051433-failed-6.18-1a2993227e8a@kernel.org' --subject-prefix 'PATCH 6.18.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