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 8E498367B89; Thu, 30 Jul 2026 14:49:29 +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=1785422970; cv=none; b=k8zhcFtr+nJaMp7yVJ0BYdHjE/opErDP2x/guIyHF6UHIc4KtuEITSTvS3xJgWjC2NmfxtzB/epOQFdHjmXPd/XqdqCCh/tRO1dQmmO0aE/ZG52CB+9/0v5zl2bZbAZq3iM4dMfNM12iku6POVEVr43FkIHqzjyqn4WEfwpTIGI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785422970; c=relaxed/simple; bh=wSIywQxr+LTA9x+8yTj0ES08AqlwAMMDryyHx+5S7XU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=pyglFAFtvyis7cxgY9ChN5epUibmS2mRXmOzkcuNiUlk4YlrNNNKCKU0wtQ08aaDu2KMkTFw7coXPRXgryheK78XarJKmaF3KHbnZ9F9a+sRQXjW7OrLTPH+An8WKn6kq6o1EwAyYK3+4k/lEZu/MZciB+FMrJ+1cDXTRKHnIS4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=EJ8N4E/G; 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="EJ8N4E/G" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F0A3B1F000E9; Thu, 30 Jul 2026 14:49:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1785422969; bh=F1NjZjOqyeZ96eZ5OvrByaSPDbKReClMW65NdYumBQs=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=EJ8N4E/G5P67ZBfE0c/JXkUqfKHZaJuDCUeTgdtiWSnTmu5gjUHQO73omR+pwW/5W bqyc52y8jsmloDtLUfwhPUIVsnML9E/d+CSS/FIa5c44rpramMSDejbyaJsdyaSPMC av6z9bk0S32QXSGI9pI9xXb8RUUG1xvV5drABYNM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Wei Yang , David Hildenbrand , Lance Yang , Balbir Singh , Klara Modin , SeongJae Park , Zi Yan , Lorenzo Stoakes , Andrew Morton Subject: [PATCH 7.1 620/744] mm/page_vma_mapped: fix device-private PMD handling Date: Thu, 30 Jul 2026 16:14:53 +0200 Message-ID: <20260730141457.452254915@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260730141444.267951807@linuxfoundation.org> References: <20260730141444.267951807@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Wei Yang commit f84ca9b1888d8fce7dfefe0e750fa971f8797486 upstream. Commit 65edfda6f3f2 ("mm/rmap: extend rmap and migration support device-private entries") introduced the concept of device-private PMD entries, but did not correctly update the rmap walk code to account for them. As a result, when page_vma_mapped_walk() encounters device-private PMD entries, it takes no action other than to acquire the PMD lock and exit. However this is highly problematic for two reasons - firstly, device private entries possess a PFN so check_pmd() needs to be called to ensure an overlapping PFN range. Secondly, and more importantly, if PVMW_MIGRATION is set the caller assumes the returned entry is a migration entry, resulting in memory corruption when the caller tries to interpret the device private entry as such. In addition, commit 146287290023 ("mm/huge_memory: implement device-private THP splitting") allowed device private PMDs to be split like THP mappings, but again did not update this code path. As a result, we might race a PMD split prior to acquiring the PMD lock. This patch addresses all of these issues by invoking check_pmd(), ensuring PMVW_MIGRATION is not set and checks whether a split raced us we do for PMD THP and migration entries. Instead of checking for a subset of the cases after taking the pmd_lock(), put device-private along with pmd_trans_huge() and pmd_is_migration_entry(). Also remove thp_migration_supported() as it is already guarded by pmd_is_migration_entry(). [akpm@linux-foundation.org: fix Raspberry Pi 1 build, per David] Link: https://lore.kernel.org/20260630021540.17297-1-richard.weiyang@gmail.com Fixes: 65edfda6f3f2 ("mm/rmap: extend rmap and migration support device-private entries") Signed-off-by: Wei Yang Suggested-by: David Hildenbrand Reviewed-by: Lance Yang Acked-by: Balbir Singh Tested-by: Klara Modin Cc: SeongJae Park Cc: Zi Yan Cc: Lorenzo Stoakes Cc: q Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/page_vma_mapped.c | 31 +++++++++++++++++-------------- 1 file changed, 17 insertions(+), 14 deletions(-) --- a/mm/page_vma_mapped.c +++ b/mm/page_vma_mapped.c @@ -242,21 +242,31 @@ restart: */ pmde = pmdp_get_lockless(pvmw->pmd); - if (pmd_trans_huge(pmde) || pmd_is_migration_entry(pmde)) { + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && + (pmd_trans_huge(pmde) || pmd_is_migration_entry(pmde) || + pmd_is_device_private_entry(pmde))) { pvmw->ptl = pmd_lock(mm, pvmw->pmd); pmde = *pvmw->pmd; - if (!pmd_present(pmde)) { + if (pmd_is_migration_entry(pmde)) { softleaf_t entry; - if (!thp_migration_supported() || - !(pvmw->flags & PVMW_MIGRATION)) + if (!(pvmw->flags & PVMW_MIGRATION)) return not_found(pvmw); entry = softleaf_from_pmd(pmde); + if (!check_pmd(softleaf_to_pfn(entry), pvmw)) + return not_found(pvmw); + return true; + } else if (pmd_is_device_private_entry(pmde)) { + softleaf_t entry; - if (!softleaf_is_migration(entry) || - !check_pmd(softleaf_to_pfn(entry), pvmw)) + if (pvmw->flags & PVMW_MIGRATION) + return not_found(pvmw); + entry = softleaf_from_pmd(pmde); + if (!check_pmd(softleaf_to_pfn(entry), pvmw)) return not_found(pvmw); return true; + } else if (!pmd_present(pmde)) { + return not_found(pvmw); } if (likely(pmd_trans_huge(pmde))) { if (pvmw->flags & PVMW_MIGRATION) @@ -265,17 +275,10 @@ restart: return not_found(pvmw); return true; } - /* THP pmd was split under us: handle on pte level */ + /* THP/device-private pmd was split under us: handle on pte level */ spin_unlock(pvmw->ptl); pvmw->ptl = NULL; } else if (!pmd_present(pmde)) { - const softleaf_t entry = softleaf_from_pmd(pmde); - - if (softleaf_is_device_private(entry)) { - pvmw->ptl = pmd_lock(mm, pvmw->pmd); - return true; - } - if ((pvmw->flags & PVMW_SYNC) && thp_vma_suitable_order(vma, pvmw->address, PMD_ORDER) &&