From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C724BC2D0BF for ; Tue, 17 Dec 2019 21:56:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8B8C821582 for ; Tue, 17 Dec 2019 21:56:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="LvpzlZ+k" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726360AbfLQV4q (ORCPT ); Tue, 17 Dec 2019 16:56:46 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:25901 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726290AbfLQV4q (ORCPT ); Tue, 17 Dec 2019 16:56:46 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1576619805; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=hSE8d84YfV0TRBuqIE3TvHfXXVwzC5/7L6224fyao4A=; b=LvpzlZ+kXIX45TFS9VWNBeWodmqFhaCP6Ekk9bpi1m6soIhOQm7Tx01mPsh+XgV/EbQ4Pi TVxdJJf92h5RX2WVoLmsWDYhrZsw6mtYtfZB4StBZ67XGYojYTVrE40h8CKq0PAVNlxaf/ aMP7UCRRtNyalXiV33lDuJeaHUxujRE= Received: from mail-qv1-f70.google.com (mail-qv1-f70.google.com [209.85.219.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-1-wMWvDWrBMgK9Z3keqHM_cQ-1; Tue, 17 Dec 2019 16:56:43 -0500 X-MC-Unique: wMWvDWrBMgK9Z3keqHM_cQ-1 Received: by mail-qv1-f70.google.com with SMTP id l1so58839qvu.13 for ; Tue, 17 Dec 2019 13:56:43 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=hSE8d84YfV0TRBuqIE3TvHfXXVwzC5/7L6224fyao4A=; b=XsytuNcRmxQVwIFEYy0+bGdcD0C/Q8L8RCWcivgRR/1EYGERtyLItt0tkh8yX1vNVk LeJ0Rs5+ZrrtZUOHIu5P6OR6Zqn6WXLuQvQCOeFqnPBT3Mm9F8/WOZgAbflN8j/tvaQv jl9wsrQ6aX7c/fv3bpDU1vajP04D+763eDMeg3FNHWzq37bQAerPxXO19WgDQaN8AkMO F1DQGfrPcYSLfcDE6eadwZwpZm+UjFL2BIAHuwOeBIvcC8S1Fe8jI/I2ZwOqTH77E/+G 1++UwIh8UVjOGnOfqmV3JchRRn9jnA4lMdSrTMSsskVc2PmICO2dmWzx/5fXxHmQEVJc 4zJQ== X-Gm-Message-State: APjAAAXH5863rM7oR0xepHMMtu5RB8x9XiKTmPuBuc9zfizABfMmfNyR p5EK8uUqgK635wP1cnuGIJQaGhY1kCLZ2970ixxt5Li0fIvyMK68hiXaxLHRNmUjQe8wSiwXFiw 4ztQRkXNgupin X-Received: by 2002:a05:6214:707:: with SMTP id b7mr6932308qvz.97.1576619803180; Tue, 17 Dec 2019 13:56:43 -0800 (PST) X-Google-Smtp-Source: APXvYqxkJVTx6R82PYxH8CBMYAk4P1dJ5EjDAy6gossam+XsRnSgvrFRKTM01bOCNWxLxn1nVLa7oA== X-Received: by 2002:a05:6214:707:: with SMTP id b7mr6932279qvz.97.1576619802834; Tue, 17 Dec 2019 13:56:42 -0800 (PST) Received: from xz-x1 ([104.156.64.74]) by smtp.gmail.com with ESMTPSA id t198sm7534281qke.6.2019.12.17.13.56.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 17 Dec 2019 13:56:41 -0800 (PST) Date: Tue, 17 Dec 2019 16:56:40 -0500 From: Peter Xu To: Sean Christopherson Cc: James Hogan , Paul Mackerras , Christian Borntraeger , Janosch Frank , Paolo Bonzini , Marc Zyngier , linux-arm-kernel@lists.infradead.org, Wanpeng Li , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , kvm@vger.kernel.org, David Hildenbrand , Joerg Roedel , Cornelia Huck , linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org, Vitaly Kuznetsov , kvmarm@lists.cs.columbia.edu, Jim Mattson , David Gibson Subject: Re: [PATCH v4 01/19] KVM: x86: Allocate new rmap and large page tracking when moving memslot Message-ID: <20191217215640.GI7258@xz-x1> References: <20191217204041.10815-1-sean.j.christopherson@intel.com> <20191217204041.10815-2-sean.j.christopherson@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20191217204041.10815-2-sean.j.christopherson@intel.com> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, Dec 17, 2019 at 12:40:23PM -0800, Sean Christopherson wrote: > Reallocate a rmap array and recalcuate large page compatibility when > moving an existing memslot to correctly handle the alignment properties > of the new memslot. The number of rmap entries required at each level > is dependent on the alignment of the memslot's base gfn with respect to > that level, e.g. moving a large-page aligned memslot so that it becomes > unaligned will increase the number of rmap entries needed at the now > unaligned level. > > Not updating the rmap array is the most obvious bug, as KVM accesses > garbage data beyond the end of the rmap. KVM interprets the bad data as > pointers, leading to non-canonical #GPs, unexpected #PFs, etc... > > general protection fault: 0000 [#1] SMP > CPU: 0 PID: 1909 Comm: move_memory_reg Not tainted 5.4.0-rc7+ #139 > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 > RIP: 0010:rmap_get_first+0x37/0x50 [kvm] > Code: <48> 8b 3b 48 85 ff 74 ec e8 6c f4 ff ff 85 c0 74 e3 48 89 d8 5b c3 > RSP: 0018:ffffc9000021bbc8 EFLAGS: 00010246 > RAX: ffff00617461642e RBX: ffff00617461642e RCX: 0000000000000012 > RDX: ffff88827400f568 RSI: ffffc9000021bbe0 RDI: ffff88827400f570 > RBP: 0010000000000000 R08: ffffc9000021bd00 R09: ffffc9000021bda8 > R10: ffffc9000021bc48 R11: 0000000000000000 R12: 0030000000000000 > R13: 0000000000000000 R14: ffff88827427d700 R15: ffffc9000021bce8 > FS: 00007f7eda014700(0000) GS:ffff888277a00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007f7ed9216ff8 CR3: 0000000274391003 CR4: 0000000000162eb0 > Call Trace: > kvm_mmu_slot_set_dirty+0xa1/0x150 [kvm] > __kvm_set_memory_region.part.64+0x559/0x960 [kvm] > kvm_set_memory_region+0x45/0x60 [kvm] > kvm_vm_ioctl+0x30f/0x920 [kvm] > do_vfs_ioctl+0xa1/0x620 > ksys_ioctl+0x66/0x70 > __x64_sys_ioctl+0x16/0x20 > do_syscall_64+0x4c/0x170 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > RIP: 0033:0x7f7ed9911f47 > Code: <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 21 6f 2c 00 f7 d8 64 89 01 48 > RSP: 002b:00007ffc00937498 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 > RAX: ffffffffffffffda RBX: 0000000001ab0010 RCX: 00007f7ed9911f47 > RDX: 0000000001ab1350 RSI: 000000004020ae46 RDI: 0000000000000004 > RBP: 000000000000000a R08: 0000000000000000 R09: 00007f7ed9214700 > R10: 00007f7ed92149d0 R11: 0000000000000246 R12: 00000000bffff000 > R13: 0000000000000003 R14: 00007f7ed9215000 R15: 0000000000000000 > Modules linked in: kvm_intel kvm irqbypass > ---[ end trace 0c5f570b3358ca89 ]--- > > The disallow_lpage tracking is more subtle. Failure to update results > in KVM creating large pages when it shouldn't, either due to stale data > or again due to indexing beyond the end of the metadata arrays, which > can lead to memory corruption and/or leaking data to guest/userspace. > > Note, the arrays for the old memslot are freed by the unconditional call > to kvm_free_memslot() in __kvm_set_memory_region(). > > Fixes: 05da45583de9b ("KVM: MMU: large page support") > Cc: stable@vger.kernel.org > Signed-off-by: Sean Christopherson Reviewed-by: Peter Xu I think the error-prone part is: new = old = *slot; Where IMHO it would be better if we only copy pointers explicitly when under control, rather than blindly copying all the pointers in the structure which even contains sub-structures. For example, I see PPC has this: struct kvm_arch_memory_slot { #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE unsigned long *rmap; #endif /* CONFIG_KVM_BOOK3S_HV_POSSIBLE */ }; I started to look into HV code of it a bit, then I see... - kvm_arch_create_memslot(kvmppc_core_create_memslot_hv) init slot->arch.rmap, - kvm_arch_flush_shadow_memslot(kvmppc_core_flush_memslot_hv) didn't free it, - kvm_arch_prepare_memory_region(kvmppc_core_prepare_memory_region_hv) is nop. So Does it have similar issue? -- Peter Xu