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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 DDD51C433DB for ; Thu, 25 Feb 2021 09:24:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 91AD464EBA for ; Thu, 25 Feb 2021 09:24:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236258AbhBYJYY (ORCPT ); Thu, 25 Feb 2021 04:24:24 -0500 Received: from wforward2-smtp.messagingengine.com ([64.147.123.31]:33903 "EHLO wforward2-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236346AbhBYJYI (ORCPT ); Thu, 25 Feb 2021 04:24:08 -0500 Received: from compute4.internal (compute4.nyi.internal [10.202.2.44]) by mailforward.west.internal (Postfix) with ESMTP id B9279D4C; Thu, 25 Feb 2021 04:23:01 -0500 (EST) Received: from mailfrontend2 ([10.202.2.163]) by compute4.internal (MEProxy); Thu, 25 Feb 2021 04:23:02 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:content-type :date:from:message-id:mime-version:subject:to:x-me-proxy :x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s=fm2; bh=m+HjCX 2h6tPr+RQDdw/IHEzRiuitlTy30quL2VrSghU=; b=sk2gHWdet0+gphFJy3Vpj6 YblUuK4IJUpC6msaADbD5k5hdXqzPhPyVM/Tx4Rr9ARA2pyWoQOiF4Oot6B4lh7f MloM0WFACvfvNSZy1aVUJ87nVRM5/Ny2/6uX3fkwjZIt/JMTQkmvlOOSVzDdqZTU Tn/k51ymOZKQB1XsrCsv3VvljleyDkq55hoxzm2fSUlQoF2gzTECFPcP5NDgRgxV 8dCqrdVSObLcSTb2vqpMA4B/iRY6WXj4V1HE9g4AUIZpw62zaf5xaA0yBnVyzYGl c294PHaWZ/Es+/p1/kOFlJXiyXCN3KqLTiylFiojjsle5fxg8E4f/D8v/d5ZDEhw == X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeduledrkeelgddtfecutefuodetggdotefrodftvf curfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfghnecu uegrihhlohhuthemuceftddtnecunecujfgurhepuffvhfffkfggtgfgsehtkeertddttd flnecuhfhrohhmpeeoghhrvghgkhhhsehlihhnuhigfhhouhhnuggrthhiohhnrdhorhhg qeenucggtffrrghtthgvrhhnpeeiteevheeuvdfhtdfgvdeiieehheefleevveehjedute evueevledujeejgfetheenucfkphepkeefrdekiedrjeegrdeigeenucevlhhushhtvghr ufhiiigvpedtnecurfgrrhgrmhepmhgrihhlfhhrohhmpehgrhgvgheskhhrohgrhhdrtg homh X-ME-Proxy: Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) by mail.messagingengine.com (Postfix) with ESMTPA id 1448D1080059; Thu, 25 Feb 2021 04:23:00 -0500 (EST) Subject: FAILED: patch "[PATCH] KVM: do not assume PTE is writable after follow_pfn" failed to apply to 4.9-stable tree To: pbonzini@redhat.com, jannh@google.com, jgg@ziepe.ca, stevensd@google.com Cc: From: Date: Thu, 25 Feb 2021 10:22:56 +0100 Message-ID: <161424497675133@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From bd2fae8da794b55bf2ac02632da3a151b10e664c Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Mon, 1 Feb 2021 05:12:11 -0500 Subject: [PATCH] KVM: do not assume PTE is writable after follow_pfn In order to convert an HVA to a PFN, KVM usually tries to use the get_user_pages family of functinso. This however is not possible for VM_IO vmas; in that case, KVM instead uses follow_pfn. In doing this however KVM loses the information on whether the PFN is writable. That is usually not a problem because the main use of VM_IO vmas with KVM is for BARs in PCI device assignment, however it is a bug. To fix it, use follow_pte and check pte_write while under the protection of the PTE lock. The information can be used to fail hva_to_pfn_remapped or passed back to the caller via *writable. Usage of follow_pfn was introduced in commit add6a0cd1c5b ("KVM: MMU: try to fix up page faults before giving up", 2016-07-05); however, even older version have the same issue, all the way back to commit 2e2e3738af33 ("KVM: Handle vma regions with no backing page", 2008-07-20), as they also did not check whether the PFN was writable. Fixes: 2e2e3738af33 ("KVM: Handle vma regions with no backing page") Reported-by: David Stevens Cc: 3pvd@google.com Cc: Jann Horn Cc: Jason Gunthorpe Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 8367d88ce39b..335a1a2b8edc 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1904,9 +1904,11 @@ static int hva_to_pfn_remapped(struct vm_area_struct *vma, kvm_pfn_t *p_pfn) { unsigned long pfn; + pte_t *ptep; + spinlock_t *ptl; int r; - r = follow_pfn(vma, addr, &pfn); + r = follow_pte(vma->vm_mm, addr, NULL, &ptep, NULL, &ptl); if (r) { /* * get_user_pages fails for VM_IO and VM_PFNMAP vmas and does @@ -1921,14 +1923,19 @@ static int hva_to_pfn_remapped(struct vm_area_struct *vma, if (r) return r; - r = follow_pfn(vma, addr, &pfn); + r = follow_pte(vma->vm_mm, addr, NULL, &ptep, NULL, &ptl); if (r) return r; + } + if (write_fault && !pte_write(*ptep)) { + pfn = KVM_PFN_ERR_RO_FAULT; + goto out; } if (writable) - *writable = true; + *writable = pte_write(*ptep); + pfn = pte_pfn(*ptep); /* * Get a reference here because callers of *hva_to_pfn* and @@ -1943,6 +1950,8 @@ static int hva_to_pfn_remapped(struct vm_area_struct *vma, */ kvm_get_pfn(pfn); +out: + pte_unmap_unlock(ptep, ptl); *p_pfn = pfn; return 0; }