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[2620:137:e000::1:20]) by mx.google.com with ESMTP id h3-20020a056402280300b004617facf124si12711128ede.253.2022.12.05.07.15.19; Mon, 05 Dec 2022 07:15:44 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=GytRASSE; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230439AbiLEPKJ (ORCPT + 99 others); Mon, 5 Dec 2022 10:10:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38558 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230133AbiLEPKI (ORCPT ); Mon, 5 Dec 2022 10:10:08 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 14E662DEA for ; Mon, 5 Dec 2022 07:09:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1670252946; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=wCUtg5FcsUQwOADbST/llFiOMmNdwZ1JtuiEKYhv/ys=; b=GytRASSE3KMocfWtppUDcKvRslFgQjUOuO4sEtIaNHZCuFh5znDRUtFj9anFt5rh604o/D +IUiAW6eL3wbZp1119jVLpuRx7MLIsvpypo95XEENyAZGbytU4UKhcpxttkgQ1eZou19Vq oWyFj2h2YuEreK86ii9F+cN7ybb00WU= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-321-aBHwKjzhPjmvTRuXu5w43Q-1; Mon, 05 Dec 2022 10:09:03 -0500 X-MC-Unique: aBHwKjzhPjmvTRuXu5w43Q-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 60CB31C07822; Mon, 5 Dec 2022 15:09:02 +0000 (UTC) Received: from t480s.fritz.box (unknown [10.39.193.244]) by smtp.corp.redhat.com (Postfix) with ESMTP id 747B340C206B; Mon, 5 Dec 2022 15:09:00 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, David Hildenbrand , Andrew Morton , Peter Xu , Yang Shi , Hugh Dickins , Andrea Arcangeli Subject: [PATCH v1] mm/swap: fix SWP_PFN_BITS with CONFIG_PHYS_ADDR_T_64BIT on 32bit Date: Mon, 5 Dec 2022 16:08:57 +0100 Message-Id: <20221205150857.167583-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1751387570294024840?= X-GMAIL-MSGID: =?utf-8?q?1751387570294024840?= We use "unsigned long" to store a PFN in the kernel and phys_addr_t to store a physical address. On a 64bit system, both are 64bit wide. However, on a 32bit system, the latter might be 64bit wide. This is, for example, the case on x86 with PAE: phys_addr_t and PTEs are 64bit wide, while "unsigned long" only spans 32bit. The current definition of SWP_PFN_BITS without MAX_PHYSMEM_BITS misses that case, and assumes that the maximum PFN is limited by a 32bit phys_addr_t. This implies, that SWP_PFN_BITS will currently only be able to cover 4 GiB - 1 on any 32bit system, which is wrong. We can end up masking off valid PFN bits from the swap offset. Ideally, we'd use something like "sizeof(phys_addr_t) * 8 - PAGE_SHIFT", however, we might exceed SWP_TYPE_SHIFT and make the BUILD_BUG_ON() in is_pfn_swap_entry() unhappy. Note that swp_entry_t is effectively an unsigned long. Consequently, simply rely on SWP_TYPE_SHIFT in case we're on 32bit and CONFIG_PHYS_ADDR_T_64BIT is defined. For example, on an 8 GiB x86 PAE system, we currently fail removing migration entries (remove_migration_ptes()) that target PFNs above 4 GiB, because mm/page_vma_mapped.c:check_pte() will fail to identify a PFN match as swp_offset_pfn() wrongly masks off valid PFN bits. With THP, split_huge_page_to_list()->...->remap_page() will leave migration entries in place and continue to unlock the page, which is wrong. Later, when we stumble over these migration entries (e.g., via /proc/self/pagemap), pfn_swap_entry_to_page() will BUG_ON() because these migration entries shouldn't exist anymore and the page was unlocked. [ 33.067591] kernel BUG at include/linux/swapops.h:497! [ 33.067597] invalid opcode: 0000 [#1] PREEMPT SMP NOPTI [ 33.067602] CPU: 3 PID: 742 Comm: cow Tainted: G E 6.1.0-rc8+ #16 [ 33.067605] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-1.fc36 04/01/2014 [ 33.067606] EIP: pagemap_pmd_range+0x644/0x650 [ 33.067612] Code: 00 00 00 00 66 90 89 ce b9 00 f0 ff ff e9 ff fb ... [ 33.067615] EAX: ee394000 EBX: 00000002 ECX: ee394000 EDX: 00000000 [ 33.067617] ESI: c1b0ded4 EDI: 00024a00 EBP: c1b0ddb4 ESP: c1b0dd68 [ 33.067619] DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068 EFLAGS: 00010246 [ 33.067624] CR0: 80050033 CR2: b7a00000 CR3: 01bbbd20 CR4: 00350ef0 [ 33.067625] Call Trace: [ 33.067628] ? madvise_free_pte_range+0x720/0x720 [ 33.067632] ? smaps_pte_range+0x4b0/0x4b0 [ 33.067634] walk_pgd_range+0x325/0x720 [ 33.067637] ? mt_find+0x1d6/0x3a0 [ 33.067641] ? mt_find+0x1d6/0x3a0 [ 33.067643] __walk_page_range+0x164/0x170 [ 33.067646] walk_page_range+0xf9/0x170 [ 33.067648] ? __kmem_cache_alloc_node+0x2a8/0x340 [ 33.067653] pagemap_read+0x124/0x280 [ 33.067658] ? default_llseek+0x101/0x160 [ 33.067662] ? smaps_account+0x1d0/0x1d0 [ 33.067664] vfs_read+0x90/0x290 [ 33.067667] ? do_madvise.part.0+0x24b/0x390 [ 33.067669] ? debug_smp_processor_id+0x12/0x20 [ 33.067673] ksys_pread64+0x58/0x90 [ 33.067675] __ia32_sys_ia32_pread64+0x1b/0x20 [ 33.067680] __do_fast_syscall_32+0x4c/0xc0 [ 33.067683] do_fast_syscall_32+0x29/0x60 [ 33.067686] do_SYSENTER_32+0x15/0x20 [ 33.067689] entry_SYSENTER_32+0x98/0xf1 Fixes: 0d206b5d2e0d ("mm/swap: add swp_offset_pfn() to fetch PFN from swap entry") Cc: Andrew Morton Cc: Peter Xu Cc: Yang Shi Cc: Hugh Dickins Cc: Andrea Arcangeli Signed-off-by: David Hildenbrand --- This makes my x86 PAE case work as expected again. Only cross compiled on other architectures. --- include/linux/swapops.h | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) base-commit: 76dcd734eca23168cb008912c0f69ff408905235 diff --git a/include/linux/swapops.h b/include/linux/swapops.h index 86b95ccb81bb..4bb7a20f3fa5 100644 --- a/include/linux/swapops.h +++ b/include/linux/swapops.h @@ -32,11 +32,13 @@ * store PFN, we only need SWP_PFN_BITS bits. Each of the pfn swap entries * can use the extra bits to store other information besides PFN. */ -#ifdef MAX_PHYSMEM_BITS +#if defined(MAX_PHYSMEM_BITS) #define SWP_PFN_BITS (MAX_PHYSMEM_BITS - PAGE_SHIFT) -#else /* MAX_PHYSMEM_BITS */ +#elif !defined(CONFIG_64BIT) && defined(CONFIG_PHYS_ADDR_T_64BIT) +#define SWP_PFN_BITS SWP_TYPE_SHIFT +#else #define SWP_PFN_BITS (BITS_PER_LONG - PAGE_SHIFT) -#endif /* MAX_PHYSMEM_BITS */ +#endif /* defined(MAX_PHYSMEM_BITS) */ #define SWP_PFN_MASK (BIT(SWP_PFN_BITS) - 1) /**