From patchwork Fri Apr 28 09:27:53 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Claudio Imbrenda X-Patchwork-Id: 13226137 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 E919FC77B7F for ; Fri, 28 Apr 2023 09:29:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345614AbjD1J3X (ORCPT ); Fri, 28 Apr 2023 05:29:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49268 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345848AbjD1J3H (ORCPT ); Fri, 28 Apr 2023 05:29:07 -0400 Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AFBCA6A74; Fri, 28 Apr 2023 02:28:28 -0700 (PDT) Received: from pps.filterd (m0353727.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 33S9RuwS007810; Fri, 28 Apr 2023 09:28:03 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : content-transfer-encoding : mime-version; s=pp1; bh=oSU/ybL2zzGUTrYzf9n7Vec87nb0Ddx26dEQX1P5FyM=; b=hhcLMMjVquOCZ4r/SESeqj9nIG7GJPuQ4M6ss13OQZL7mLmy3pyGulX/TVP3uwGSvvEb 8sRm1CIAj2s2G27yr46UZLdfwqWnvXbTNzmlFHx12/vZM6NfXXYIo396xauSM/gzZssx ir4L5LDV3F5Utpz9JO32/wgjuGsb0nC9axOscMs+j+avMTXY164/ZjjrRsjHaugU1/Dn S0RhbbqjHxLKX2q7EWs76DsDqS/vwDa3JufzLgzOtU8ZI2ycKEM5uknnsyQBNVEd2C4K H2fJo8qP4hZE1qC0pp9I4ZoiW76Vj8dK/JA3TnlUy3hSHyOCIeOddHZfgOu1a7m6FBF6 cA== Received: from ppma04ams.nl.ibm.com (63.31.33a9.ip4.static.sl-reverse.com [169.51.49.99]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 3q8avb198t-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 28 Apr 2023 09:28:02 +0000 Received: from pps.filterd (ppma04ams.nl.ibm.com [127.0.0.1]) by ppma04ams.nl.ibm.com (8.17.1.19/8.17.1.19) with ESMTP id 33S2vVFN001400; Fri, 28 Apr 2023 09:28:00 GMT Received: from smtprelay02.fra02v.mail.ibm.com ([9.218.2.226]) by ppma04ams.nl.ibm.com (PPS) with ESMTPS id 3q47773ffx-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 28 Apr 2023 09:28:00 +0000 Received: from smtpav04.fra02v.mail.ibm.com (smtpav04.fra02v.mail.ibm.com [10.20.54.103]) by smtprelay02.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 33S9RsCN4129526 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 28 Apr 2023 09:27:54 GMT Received: from smtpav04.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id F1DDA20043; Fri, 28 Apr 2023 09:27:53 +0000 (GMT) Received: from smtpav04.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A92402004D; Fri, 28 Apr 2023 09:27:53 +0000 (GMT) Received: from p-imbrenda.boeblingen.de.ibm.com (unknown [9.152.224.56]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTP; Fri, 28 Apr 2023 09:27:53 +0000 (GMT) From: Claudio Imbrenda To: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, frankja@linux.ibm.com, borntraeger@de.ibm.com, nrb@linux.ibm.com, nsg@linux.ibm.com, seiden@linux.ibm.com, jgg@nvidia.com, hca@linux.ibm.com Subject: [PATCH v3 1/1] KVM: s390: fix race in gmap_make_secure() Date: Fri, 28 Apr 2023 11:27:53 +0200 Message-Id: <20230428092753.27913-2-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230428092753.27913-1-imbrenda@linux.ibm.com> References: <20230428092753.27913-1-imbrenda@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-GUID: z3xKEHHfgRqQwIwHtvKHdyG1w4PbqnBj X-Proofpoint-ORIG-GUID: z3xKEHHfgRqQwIwHtvKHdyG1w4PbqnBj X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.254,Aquarius:18.0.942,Hydra:6.0.573,FMLib:17.11.170.22 definitions=2023-04-28_04,2023-04-27_01,2023-02-09_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 mlxscore=0 suspectscore=0 phishscore=0 adultscore=0 lowpriorityscore=0 bulkscore=0 clxscore=1015 mlxlogscore=922 impostorscore=0 malwarescore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2303200000 definitions=main-2304280073 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Fix a potential race in gmap_make_secure() and remove the last user of follow_page() without FOLL_GET. The old code is locking something it doesn't have a reference to, and as explained by Jason and David in this discussion: https://lore.kernel.org/linux-mm/Y9J4P%2FRNvY1Ztn0Q@nvidia.com/ it can lead to all kind of bad things, including the page getting unmapped (MADV_DONTNEED), freed, reallocated as a larger folio and the unlock_page() would target the wrong bit. There is also another race with the FOLL_WRITE, which could race between the follow_page() and the get_locked_pte(). The main point is to remove the last use of follow_page() without FOLL_GET or FOLL_PIN, removing the races can be considered a nice bonus. Signed-off-by: Claudio Imbrenda Link: https://lore.kernel.org/linux-mm/Y9J4P%2FRNvY1Ztn0Q@nvidia.com/ Suggested-by: Jason Gunthorpe Fixes: 214d9bbcd3a6 ("s390/mm: provide memory management functions for protected KVM guests") Reviewed-by: Jason Gunthorpe --- arch/s390/kernel/uv.c | 32 +++++++++++--------------------- 1 file changed, 11 insertions(+), 21 deletions(-) diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c index 9f18a4af9c13..cb2ee06df286 100644 --- a/arch/s390/kernel/uv.c +++ b/arch/s390/kernel/uv.c @@ -192,21 +192,10 @@ static int expected_page_refs(struct page *page) return res; } -static int make_secure_pte(pte_t *ptep, unsigned long addr, - struct page *exp_page, struct uv_cb_header *uvcb) +static int make_page_secure(struct page *page, struct uv_cb_header *uvcb) { - pte_t entry = READ_ONCE(*ptep); - struct page *page; int expected, cc = 0; - if (!pte_present(entry)) - return -ENXIO; - if (pte_val(entry) & _PAGE_INVALID) - return -ENXIO; - - page = pte_page(entry); - if (page != exp_page) - return -ENXIO; if (PageWriteback(page)) return -EAGAIN; expected = expected_page_refs(page); @@ -304,17 +293,18 @@ int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb) goto out; rc = -ENXIO; - page = follow_page(vma, uaddr, FOLL_WRITE); - if (IS_ERR_OR_NULL(page)) - goto out; - - lock_page(page); ptep = get_locked_pte(gmap->mm, uaddr, &ptelock); - if (should_export_before_import(uvcb, gmap->mm)) - uv_convert_from_secure(page_to_phys(page)); - rc = make_secure_pte(ptep, uaddr, page, uvcb); + if (pte_present(*ptep) && !(pte_val(*ptep) & _PAGE_INVALID) && pte_write(*ptep)) { + page = pte_page(*ptep); + rc = -EAGAIN; + if (trylock_page(page)) { + if (should_export_before_import(uvcb, gmap->mm)) + uv_convert_from_secure(page_to_phys(page)); + rc = make_page_secure(page, uvcb); + unlock_page(page); + } + } pte_unmap_unlock(ptep, ptelock); - unlock_page(page); out: mmap_read_unlock(gmap->mm);