From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-218731-1516388259-2-9124142350826906565 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, FREEMAIL_FORGED_FROMDOMAIN 0.25, FREEMAIL_FROM 0.001, FSL_HELO_FAKE 3.899, HEADER_FROM_DIFFERENT_DOMAINS 0.25, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='US', FromHeader='com', MailFrom='org' X-Spam-charsets: cc='utf-8', plain='us-ascii' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: stable-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1516388259; b=g02Md04XLjpo+uHeBdGpj4KntZSAf4tW5XJI8BwqSkj/Aq8 HiDJT6qJFoyqRpCDu4TV2uieghWHhUqySTdvTn02M5OOhK9rFum/hGeF2oocan1O 4xqChWBpFAma8B1tcfcFWS3YZz9rXsxxbfJ/EpBuMPgfA6NX3sr4NXQma7K/k9HQ 6c16bUot0CuzN+OesnE122G0BmVlnjxjw9X9XPH2pioBnXqv8lj89tsVFmqIsm43 BM4lYLJrEuvdU29CUMRCbi1lciQpqQ4rKncX0zYvUQQnVTKpjPQdg6SZ9G2QPzt/ dl7qIGKp+/9jNb3txCAE/Hc3x74EdUzQe6lLNxw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=date:from:to:cc:subject:message-id :references:mime-version:content-type:in-reply-to:sender :list-id; s=arctest; t=1516388259; bh=8iUZQvkeT0DpnVbQRlLCUoHFNw DFHaIJWhGXtG7c2RU=; b=L1GalXd+lpxKDtXn3tqiKcaUjD46MzjcIzafg7/R13 Ye0v3LT5xaKaNaPZh6lWKtH+/wi7ndNPB6mXlpuxDtVode36tzCN4w+pGoUmyGpT hbP0ttwvAQE8dNGwj3445GdFsDbWinnYny0+2G++tC2USUo2DCHXGUibD93tHktS BGZNvypVpWHjhDuOwfG4QoLS/GNP4X9GhgzO5QNCHvTJyxolK6Ho9l1mh/YuJRc+ tPd9oGn45oI1XedL7J4kAZcKKI8hlgh2GHSbYay2EqjHzDI0W5k6eqfwlTmxfU0r sZTNmMH1SXP6Hmgua2Fhypwmn7BSAL+8hp93eD6u4+Gw== ARC-Authentication-Results: i=1; mx3.messagingengine.com; arc=none (no signatures found); dkim=pass (2048-bit rsa key sha256) header.d=gmail.com header.i=@gmail.com header.b=lok1Myp1 x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=20161025; dmarc=pass (p=none,has-list-id=yes,d=none) header.from=gmail.com; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-google-dkim=pass (2048-bit rsa key) header.d=1e100.net header.i=@1e100.net header.b=X/BWcVMS; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=gmail.com header.result=pass header_is_org_domain=yes Authentication-Results: mx3.messagingengine.com; arc=none (no signatures found); dkim=pass (2048-bit rsa key sha256) header.d=gmail.com header.i=@gmail.com header.b=lok1Myp1 x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=20161025; dmarc=pass (p=none,has-list-id=yes,d=none) header.from=gmail.com; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-google-dkim=pass (2048-bit rsa key) header.d=1e100.net header.i=@1e100.net header.b=X/BWcVMS; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=gmail.com header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755993AbeASS5W (ORCPT ); Fri, 19 Jan 2018 13:57:22 -0500 Received: from mail-io0-f194.google.com ([209.85.223.194]:40857 "EHLO mail-io0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755830AbeASS5U (ORCPT ); Fri, 19 Jan 2018 13:57:20 -0500 X-Google-Smtp-Source: ACJfBotQICgyb45MMJ1lWyeIM/1hnlZ7biaFo4e4WqA7g48h96PANJSUdbfhYfJuznzUz2tXvLiG1w== Date: Fri, 19 Jan 2018 10:57:16 -0800 From: Eric Biggers To: Wanpeng Li Cc: kvm , Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, Eric Biggers , "# v3 . 10+" , Alex Williamson Subject: Re: [PATCH] KVM: prevent overlap between user and private memslots Message-ID: <20180119185716.rmjh7nts6cubkvgw@gmail.com> References: <94eb2c06f65e7ece95055cf1aafd@google.com> <20180119081820.30803-1-ebiggers3@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170609 (1.8.3) Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: +Cc alex.williamson@redhat.com On Fri, Jan 19, 2018 at 05:03:47PM +0800, Wanpeng Li wrote: > 2018-01-19 17:01 GMT+08:00 Wanpeng Li : > > 2018-01-19 16:18 GMT+08:00 Eric Biggers : > >> From: Eric Biggers > >> > >> Memslots must not overlap in guest physical memory, since otherwise some > >> guest physical addresses will not uniquely map to a memslot. Yet, the > >> overlap check in __kvm_set_memory_region() allows a memslot that > >> overlaps one of the "private" memslots, e.g. the memslot reserved for > >> the TSS on x86. > >> > >> This seems to be a very old bug that was introduced years ago when > >> private memory slots were first added. It seems that later refactoring > >> incorrectly assumed this bug was intentional and preserved it. > >> > >> Fix it by removing the loophole for private memslots, so we just check > >> for overlap against all memslots. > >> > >> This bug was found by syzkaller, which used a memslot overlap to make > >> pte_list_remove() be called for the wrong memslot, hitting a BUG(): > >> > >> pte_list_remove: 000000007185ed42 0->BUG > >> kernel BUG at arch/x86/kvm/mmu.c:1209! > >> [...] > >> RIP: 0010:pte_list_remove+0x107/0x110 arch/x86/kvm/mmu.c:1208 > >> [...] > >> Call Trace: > >> mmu_page_zap_pte+0x7e/0xd0 arch/x86/kvm/mmu.c:2499 > >> kvm_mmu_page_unlink_children arch/x86/kvm/mmu.c:2521 [inline] > >> kvm_mmu_prepare_zap_page+0x4f/0x340 arch/x86/kvm/mmu.c:2565 > >> kvm_zap_obsolete_pages arch/x86/kvm/mmu.c:5348 [inline] > >> kvm_mmu_invalidate_zap_all_pages+0xa6/0x100 arch/x86/kvm/mmu.c:5389 > >> kvm_mmu_notifier_release+0x4f/0x80 arch/x86/kvm/../../../virt/kvm/kvm_main.c:468 > >> __mmu_notifier_release+0x63/0x100 mm/mmu_notifier.c:75 > >> mmu_notifier_release include/linux/mmu_notifier.h:244 [inline] > >> exit_mmap+0x160/0x170 mm/mmap.c:3009 > >> __mmput kernel/fork.c:966 [inline] > >> mmput+0x44/0xd0 kernel/fork.c:987 > >> exit_mm kernel/exit.c:544 [inline] > >> do_exit+0x24a/0xb50 kernel/exit.c:856 > >> do_group_exit+0x34/0xb0 kernel/exit.c:972 > >> SYSC_exit_group kernel/exit.c:983 [inline] > >> SyS_exit_group+0xb/0x10 kernel/exit.c:981 > >> entry_SYSCALL_64_fastpath+0x1e/0x8b > >> > >> Reproducer: > >> > >> #include > >> #include > >> #include > >> > >> int main() > >> { > >> static char buf[4096*3] __attribute__((aligned(4096))); > >> int kvm, vm, cpu; > >> struct kvm_mp_state mp_state = { KVM_MP_STATE_SIPI_RECEIVED }; > >> struct kvm_userspace_memory_region memreg = { > >> .memory_size = sizeof(buf), > >> .userspace_addr = (__u64)buf, > >> }; > >> > >> kvm = open("/dev/kvm", O_RDWR); > >> vm = ioctl(kvm, KVM_CREATE_VM, 0); > >> ioctl(vm, KVM_CREATE_IRQCHIP); > >> cpu = ioctl(vm, KVM_CREATE_VCPU, 0); > >> ioctl(cpu, KVM_SET_MP_STATE, &mp_state); > >> ioctl(vm, KVM_SET_TSS_ADDR, 0); > >> ioctl(cpu, KVM_RUN, 0); > >> ioctl(vm, KVM_SET_USER_MEMORY_REGION, &memreg); > >> } > >> > >> Reported-by: syzbot > >> Fixes: e0d62c7f4860 ("KVM: Add kernel-internal memory slots") > >> Cc: # v2.6.25+ > >> Signed-off-by: Eric Biggers > > > > Please refer to this one. https://patchwork.kernel.org/patch/9645377/ > > https://lkml.org/lkml/2017/3/27/57 > Ah, so this was reported before, and you sent the same fix. Well, it was never applied, so the bug is still there, and anyone who can use /dev/kvm can trigger it. So one of these patches needs to be applied, unless there is a better fix. I don't agree with the "Fixes:" line in your version of the patch. The bug was actually there prior to 5419369ed, which might explain why that commit seemed to preserve the behavior intentionally. (Note that KVM_MEMORY_SLOTS did not include the private memory slots; it was later renamed to KVM_USER_MEM_SLOTS.) Eric