From patchwork Wed Apr 13 21:11:50 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 561190 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 264C5C433F5 for ; Wed, 13 Apr 2022 21:13:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238997AbiDMVPn (ORCPT ); Wed, 13 Apr 2022 17:15:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58524 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239125AbiDMVPD (ORCPT ); Wed, 13 Apr 2022 17:15:03 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 932D8888F4; Wed, 13 Apr 2022 14:11:54 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 13FE461EAD; Wed, 13 Apr 2022 21:11:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6AFC4C385A3; Wed, 13 Apr 2022 21:11:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1649884313; bh=8rxi6kXHApSynsrGuJLcmNBMOkxcsJDtzJEZEMw7/UU=; h=Date:To:From:Subject:From; b=OFhlp9puJXFzYHM5OYctIppTsA4aag8jbwgi70TZUHFBJqZpq8zbM6ixjLPyDeJvW 8HOfjlVJe1TCafk0JeUr9KxaNuyGAcxAXedetmAUoGS30efNTGFW4OyldqEnE+qXS6 V0vzOF98l/vmuJdsTc3DL9TJQ89XKRbBIT0TaoJM= Date: Wed, 13 Apr 2022 14:11:50 -0700 To: mm-commits@vger.kernel.org, surenb@google.com, stable@vger.kernel.org, rppt@linux.ibm.com, rientjes@google.com, anshuman.khandual@arm.com, quic_sudaraja@quicinc.com, akpm@linux-foundation.org From: Andrew Morton Subject: [nacked] mm-page_alloc-check-pfn-is-valid-before-moving-to-freelist.patch removed from -mm tree Message-Id: <20220413211153.6AFC4C385A3@smtp.kernel.org> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: mm, page_alloc: check pfn is valid before moving to freelist has been removed from the -mm tree. Its filename was mm-page_alloc-check-pfn-is-valid-before-moving-to-freelist.patch This patch was dropped because it was nacked ------------------------------------------------------ From: Sudarshan Rajagopalan Subject: mm, page_alloc: check pfn is valid before moving to freelist Check if pfn is valid before or not before moving it to freelist. There are possible scenario where a pageblock can have partial physical hole and partial part of System RAM. This happens when base address in RAM partition table is not aligned to pageblock size. Example: Say we have this first two entries in RAM partition table - Base Addr: 0x0000000080000000 Length: 0x0000000058000000 Base Addr: 0x00000000E3930000 Length: 0x0000000020000000 ... Physical hole: 0xD8000000 - 0xE3930000 On system having 4K as page size and hence pageblock size being 4MB, the base address 0xE3930000 is not aligned to 4MB pageblock size. Now we will have pageblock which has partial physical hole and partial part of System RAM - Pageblock [0xE3800000 - 0xE3C00000] - 0xE3800000 - 0xE3930000 -- physical hole 0xE3930000 - 0xE3C00000 -- System RAM Now doing __alloc_pages say we get a valid page with PFN 0xE3B00 from __rmqueue_fallback, we try to put other pages from the same pageblock as well into freelist by calling steal_suitable_fallback(). We then search for freepages from start of the pageblock due to below code - move_freepages_block(zone, page, migratetype, ...) { pfn = page_to_pfn(page); start_pfn = pfn & ~(pageblock_nr_pages - 1); end_pfn = start_pfn + pageblock_nr_pages - 1; ... } With the pageblock which has partial physical hole at the beginning, we will run into PFNs from the physical hole whose struct page is not initialized and is invalid, and system would crash as we operate on invalid struct page to find out of page is in Buddy or LRU or not [ 107.629453][ T9688] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 [ 107.639214][ T9688] Mem abort info: [ 107.642829][ T9688] ESR = 0x96000006 [ 107.646696][ T9688] EC = 0x25: DABT (current EL), IL = 32 bits [ 107.652878][ T9688] SET = 0, FnV = 0 [ 107.656751][ T9688] EA = 0, S1PTW = 0 [ 107.660705][ T9688] FSC = 0x06: level 2 translation fault [ 107.666455][ T9688] Data abort info: [ 107.670151][ T9688] ISV = 0, ISS = 0x00000006 [ 107.674827][ T9688] CM = 0, WnR = 0 [ 107.678615][ T9688] user pgtable: 4k pages, 39-bit VAs, pgdp=000000098a237000 [ 107.685970][ T9688] [0000000000000000] pgd=0800000987170003, p4d=0800000987170003, pud=0800000987170003, pmd=0000000000000000 [ 107.697582][ T9688] Internal error: Oops: 96000006 [#1] PREEMPT SMP [ 108.209839][ T9688] pc : move_freepages_block+0x174/0x27c [ 108.215407][ T9688] lr : steal_suitable_fallback+0x20c/0x398 [ 108.305908][ T9688] Call trace: [ 108.309151][ T9688] move_freepages_block+0x174/0x27c [PageLRU] [ 108.314359][ T9688] steal_suitable_fallback+0x20c/0x398 [ 108.319826][ T9688] rmqueue_bulk+0x250/0x934 [ 108.324325][ T9688] rmqueue_pcplist+0x178/0x2ac [ 108.329086][ T9688] rmqueue+0x5c/0xc10 [ 108.333048][ T9688] get_page_from_freelist+0x19c/0x430 [ 108.338430][ T9688] __alloc_pages+0x134/0x424 [ 108.343017][ T9688] page_cache_ra_unbounded+0x120/0x324 [ 108.348494][ T9688] do_sync_mmap_readahead+0x1b0/0x234 [ 108.353878][ T9688] filemap_fault+0xe0/0x4c8 [ 108.358375][ T9688] do_fault+0x168/0x6cc [ 108.362518][ T9688] handle_mm_fault+0x5c4/0x848 [ 108.367280][ T9688] do_page_fault+0x3fc/0x5d0 [ 108.371867][ T9688] do_translation_fault+0x6c/0x1b0 [ 108.376985][ T9688] do_mem_abort+0x68/0x10c [ 108.381389][ T9688] el0_ia+0x50/0xbc [ 108.385175][ T9688] el0t_32_sync_handler+0x88/0xbc [ 108.390208][ T9688] el0t_32_sync+0x1b8/0x1bc Hence, avoid operating on invalid pages within the same pageblock by checking if pfn is valid or not. [akpm@linux-foundation.org: add comment, per David] Link: https://lkml.kernel.org/r/fb3c8c008994b2ed96f74b6b9698ff998b689bd2.1649794059.git.quic_sudaraja@quicinc.com Signed-off-by: Sudarshan Rajagopalan Fixes: 859a85ddf90e7140 ("mm: remove pfn_valid_within() and CONFIG_HOLES_IN_ZONE") Acked-by: David Rientjes Cc: Mike Rapoport Cc: Anshuman Khandual Cc: Suren Baghdasaryan Cc: Signed-off-by: Andrew Morton --- a/mm/page_alloc.c~mm-page_alloc-check-pfn-is-valid-before-moving-to-freelist +++ a/mm/page_alloc.c @@ -2521,6 +2521,15 @@ static int move_freepages(struct zone *z int pages_moved = 0; for (pfn = start_pfn; pfn <= end_pfn;) { + if (!pfn_valid(pfn)) { + /* + * Pageblock alignment may cause us to try to access + * into a hole + */ + pfn++; + continue; + } + page = pfn_to_page(pfn); if (!PageBuddy(page)) { /*