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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E09D0C433EF for ; Thu, 13 Jan 2022 13:22:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235092AbiAMNW1 (ORCPT ); Thu, 13 Jan 2022 08:22:27 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48782 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232688AbiAMNW0 (ORCPT ); Thu, 13 Jan 2022 08:22:26 -0500 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9E7EBC06173F; Thu, 13 Jan 2022 05:22:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=MIME-Version:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=ZADR56SLoJfsCr3mxoUjV0uwxMxpiW39hHcQiYuzurE=; b=tjz9I6UrB9u000OVaOmUCt30Fo EZTAu4NSBkOyzu3+gq/avQaycO2x2BIK2NiG1x2UQPMlC/XGbz3XmfczbbQ06OBzXvNxD22E7z4Gv qr34rOKPPLsoIyX/qLpSuH5QligESbvkLHdLMct4BE2aY6pMP+oKwh36jtJ/vJFQX9VnoQYnHjeKc g5ImML41r3Rt/Wzo65ccllkvimg6h5T7+5xlARzClRuCMI24DnLxY7aWtxpeS9Z/2d9RM+OUhRLCf zmhLVkR6Qgd3/R/dw/48OsRFOSTbBSOeBbMm2ty5waHKooJfwT8Ip5fWVRKk8jK43Y/6zg2H49kEW JXHdkwKA==; Received: from [2001:8b0:10b:1:4a2a:e3ff:fe14:8625] (helo=u3832b3a9db3152.ant.amazon.com) by bombadil.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1n803b-0065m1-Mj; Thu, 13 Jan 2022 13:22:24 +0000 Message-ID: Subject: Re: KVM: Warn if mark_page_dirty() is called without an active vCPU From: David Woodhouse To: Christian Borntraeger , Paolo Bonzini Cc: butterflyhuangxx@gmail.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, seanjc@google.com, Cornelia Huck , Janosch Frank , David Hildenbrand , linux-s390 , Thomas Huth , Claudio Imbrenda Date: Thu, 13 Jan 2022 13:22:20 +0000 In-Reply-To: References: <20220113120609.736701-1-borntraeger@linux.ibm.com> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/pkcs7-signature"; boundary="=-sjY/iKEqgTU6hTEaLceH" User-Agent: Evolution 3.36.5-0ubuntu1 MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org --=-sjY/iKEqgTU6hTEaLceH Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2022-01-13 at 13:51 +0100, Christian Borntraeger wrote: > > Btw, that get_map_page() in arch/s390/kvm/interrupt.c looks like it has > > the same use-after-free problem that kvm_map_gfn() used to have. It > > probably wants converting to the new gfn_to_pfn_cache. > >=20 > > Take a look at how I resolve the same issue for delivering Xen event > > channel interrupts. >=20 > Do you have a commit ID for your Xen event channel fix? 14243b387137 ("KVM: x86/xen: Add KVM_IRQ_ROUTING_XEN_EVTCHN and event channel delivery") and the commits reworking the gfn_to_pfn_cache which lead up to it. Questions: In your kvm_set_routing_entry() where it calls gmap_translate() to turn the summary_addr and ind_addr from guest addresses to userspace virtual addresses, what protects those translations? If the gmap changes before kvm_set_routing_entry() even returns, what ensures that the IRQ gets retranslated? And later in adapter_indicators_set() where you take that userspace virtual address and pass it to your get_map_page() function, the same question: what if userspace does a concurrent mmap() and changes the physical page that the userspace address points to?=20 In the latter case, at least it does look like you don't support external memory accessed only by a PFN without having a corresponding struct page. So at least you don't end up accessing a page that can now belong to *another* guest, because the original underlying page is locked. You're probably OK in that case, so it's just the gmap changing that we need to focus on? --=-sjY/iKEqgTU6hTEaLceH Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCEkQw ggYQMIID+KADAgECAhBNlCwQ1DvglAnFgS06KwZPMA0GCSqGSIb3DQEBDAUAMIGIMQswCQYDVQQG EwJVUzETMBEGA1UECBMKTmV3IEplcnNleTEUMBIGA1UEBxMLSmVyc2V5IENpdHkxHjAcBgNVBAoT FVRoZSBVU0VSVFJVU1QgTmV0d29yazEuMCwGA1UEAxMlVVNFUlRydXN0IFJTQSBDZXJ0aWZpY2F0 aW9uIEF1dGhvcml0eTAeFw0xODExMDIwMDAwMDBaFw0zMDEyMzEyMzU5NTlaMIGWMQswCQYDVQQG EwJHQjEbMBkGA1UECBMSR3JlYXRlciBNYW5jaGVzdGVyMRAwDgYDVQQHEwdTYWxmb3JkMRgwFgYD VQQKEw9TZWN0aWdvIExpbWl0ZWQxPjA8BgNVBAMTNVNlY3RpZ28gUlNBIENsaWVudCBBdXRoZW50 aWNhdGlvbiBhbmQgU2VjdXJlIEVtYWlsIENBMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKC AQEAyjztlApB/975Rrno1jvm2pK/KxBOqhq8gr2+JhwpKirSzZxQgT9tlC7zl6hn1fXjSo5MqXUf 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