From patchwork Tue Apr 12 20:16:23 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sudarshan Rajagopalan X-Patchwork-Id: 12811228 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5E9EAC433F5 for ; Tue, 12 Apr 2022 20:17:06 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B8E616B0075; Tue, 12 Apr 2022 16:17:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B18436B0078; Tue, 12 Apr 2022 16:17:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 993A16B007B; Tue, 12 Apr 2022 16:17:05 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0093.hostedemail.com [216.40.44.93]) by kanga.kvack.org (Postfix) with ESMTP id 880EB6B0075 for ; Tue, 12 Apr 2022 16:17:05 -0400 (EDT) Received: from smtpin31.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 35D64183E6C9E for ; Tue, 12 Apr 2022 20:17:05 +0000 (UTC) X-FDA: 79349336010.31.692EDBB Received: from alexa-out-sd-01.qualcomm.com (alexa-out-sd-01.qualcomm.com [199.106.114.38]) by imf11.hostedemail.com (Postfix) with ESMTP id 57B4640009 for ; Tue, 12 Apr 2022 20:17:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=quicinc.com; i=@quicinc.com; q=dns/txt; s=qcdkim; t=1649794624; x=1681330624; h=from:to:cc:subject:date:message-id; bh=U07zXEF5XKiHrZJWluQBPtBzbqwPfha91C4VetzKe+k=; b=BngTszu6wDXX+trcuB6Q6AygvW53cyw3RmWKqK32COLTPVGpOJDMpvDK 1BlaglE4gIqBgxKYalqeQmfOYtrWnp/aUBAfs1eTQuAW+ZNS6j2xVKAyW OVg3vUNfIyYPFjT31qzw7kNhB/XaMr45fW87iaEsHQpQRoVEzDreqP9CM Q=; Received: from unknown (HELO ironmsg-SD-alpha.qualcomm.com) ([10.53.140.30]) by alexa-out-sd-01.qualcomm.com with ESMTP; 12 Apr 2022 13:17:03 -0700 X-QCInternal: smtphost Received: from th-lint-014.qualcomm.com ([10.63.177.51]) by ironmsg-SD-alpha.qualcomm.com with ESMTP; 12 Apr 2022 13:17:02 -0700 Received: by th-lint-014.qualcomm.com (Postfix, from userid 455663) id DEC2B139C; Tue, 12 Apr 2022 13:17:02 -0700 (PDT) From: Sudarshan Rajagopalan To: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Sudarshan Rajagopalan , Mike Rapoport , Anshuman Khandual , Suren Baghdasaryan Subject: [PATCH] mm, page_alloc: check pfn is valid before moving to freelist Date: Tue, 12 Apr 2022 13:16:23 -0700 Message-Id: X-Mailer: git-send-email 2.7.4 In-Reply-To: References: In-Reply-To: References: X-Stat-Signature: ckafh1ggeu6cn9qyou83d3sz89qepnas Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=quicinc.com header.s=qcdkim header.b=BngTszu6; dmarc=pass (policy=none) header.from=quicinc.com; spf=none (imf11.hostedemail.com: domain of sudaraja@qualcomm.com has no SPF policy when checking 199.106.114.38) smtp.mailfrom=sudaraja@qualcomm.com X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 57B4640009 X-HE-Tag: 1649794624-156595 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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. Signed-off-by: Sudarshan Rajagopalan Fixes: 4c7b9896621be ("mm: remove pfn_valid_within() and CONFIG_HOLES_IN_ZONE") Cc: Mike Rapoport Cc: Anshuman Khandual Cc: Suren Baghdasaryan Acked-by: David Rientjes --- mm/page_alloc.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 6e5b448..e87aa053 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2521,6 +2521,11 @@ static int move_freepages(struct zone *zone, int pages_moved = 0; for (pfn = start_pfn; pfn <= end_pfn;) { + if (!pfn_valid(pfn)) { + pfn++; + continue; + } + page = pfn_to_page(pfn); if (!PageBuddy(page)) { /*