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=1794048893; b=oiQrzQ6QWVXdsezHaxrg2VKSmYOcairKhzyQWItrjB3ZdORdmdQ6mC3PD1YsI9JYBEQu E19UPossEi8t48Bcd+gUbatSC4RqmT/wsRqehirOkaJeCBKymOAKwwC40WEFQVsxBdqjf 1MDcg1WqCy91H+KzoqetZeMb5TUSBQ9CNBOqgrWM42vDO2UUgsDD3CKMEFPKcI/MzBiCK tz5iCigji0zl35uUDaNsqBS3cJB940tfbzZRsFB9ymoHEtI2IY7Smnb6vcfgA2wqTk2DS 0pYPlThE7uCB3hRZsWbd/vQKFreGwvl7ajD1Z4ngBNgljZxEu5SrbGKgJbQW7If94QQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794048893; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=G7wegxdXiw9VpLB6ta0svw/2MWa732rcCBlJcoALzhs=; b=XvJ5JDfkDYLGcGhRlV1Qvs2Iul7q23ZMCKOvE9H9rjx5eTdtv/j5b+NWRY1+4RXna29c f2ZWTZuArKN78/excsFDZl02SxlFEElogUkVxAbV4Q3ozL7f+h3YwGhZACfFpbuZayyUq SjBrueS3cQ3pj8k3T0w3VMRbtjYvd2wD0mrCdtv0gqxuuwcuQ33qAQdf4cZTOxkTORKHZ Cjt4eU4BzRIoH30QzCeDR4kqYi2WAKoHXVRBCEqYSZVaedXZ0D4b5UghjItsajm3Pgc+Z xQgOz1CmB/51gm8dAydLkoiYHxFTENNqDOy6PbYd5EsW1pswUE1MO8tFh5Snr+eUPBw== 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=SrKtGyYH; 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 8663C606A326 for ; Sat, 7 Nov 2026 10:54:53 +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=SrKtGyYH Received: by smtp.kernel.org (Postfix) with ESMTPSA id 46E4C1F0089F; Sat, 7 Nov 2026 10:54:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794048893; bh=G7wegxdXiw9VpLB6ta0svw/2MWa732rcCBlJcoALzhs=; h=From:To:Cc:Subject:Date; b=SrKtGyYHBsCuBkGQpqZC4fWokjV+zp1HXsXPMWqzXYISDqo2EmocTNP4MPlgOm65O Y2TlHx5aLh/zYQPfX8ecxmLa8ScBei9qw7yBng7HAW8AtGtpH5ik8+jtHKVT8oO/8D GCNcjZyPbi3uAj/7wHfMNdM6AvCdPs0DsLe5X0kMEbnHM8ggk+cKqLABGDcSject+d yqg27qC91udjQLZYzlBWp/TWMfMAAgv+s+HbDl+pmIgQdqGzgLcor6Sr4/2RJz5mfP ZHEPhNDc9EHABQuUl7fp1/qKBtCSEEmiU6kg46rit8TZTgCKaM+ykkLIuxq4gwAtU6 5nl7LB4xmRFOA== 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 6.1-stable tree Date: Sat, 7 Nov 2026 05:54:50 -0500 Message-ID: <20261107055450-failed-6.1-1a2993227e8a@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 6.1-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-6.1.y git checkout FETCH_HEAD git cherry-pick -x 1a2993227e8a27fc4cdea305bbdae82d290bc885 # git commit -s git send-email --to '' --in-reply-to '20261107055450-failed-6.1-1a2993227e8a@kernel.org' --subject-prefix 'PATCH 6.1.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