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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5E8E6C5AD49 for ; Fri, 6 Jun 2025 19:15:35 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id ED8FF6B0093; Fri, 6 Jun 2025 15:15:34 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id EB13F6B0096; Fri, 6 Jun 2025 15:15:34 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DC7506B0098; Fri, 6 Jun 2025 15:15:34 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id BAFF56B0093 for ; Fri, 6 Jun 2025 15:15:34 -0400 (EDT) Received: from smtpin09.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 46F505B854 for ; Fri, 6 Jun 2025 19:15:34 +0000 (UTC) X-FDA: 83525929788.09.9A080E8 Received: from mx0a-00364e01.pphosted.com (mx0a-00364e01.pphosted.com [148.163.135.74]) by imf10.hostedemail.com (Postfix) with ESMTP id BD598C0009 for ; Fri, 6 Jun 2025 19:15:31 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=columbia.edu header.s=pps01 header.b=DkA7DbxK; spf=pass (imf10.hostedemail.com: domain of tz2294@columbia.edu designates 148.163.135.74 as permitted sender) smtp.mailfrom=tz2294@columbia.edu; dmarc=pass (policy=none) header.from=columbia.edu ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1749237332; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=hxKpvIwDJev2AQJKrOOsefY7R3fXf+i39zjL9smzWlg=; b=7ZDSx2a6a+NUvX5vtb9N0gAEYUuRtWxyruPZg2VK8UUpixb5pxfzkecsbaGzMpwZyoHik5 6Ua+40iED7mpAlRGxXHO5vdAGwwsqEG/hh3UDpOYkHOH29ROeZOy/BJ+hj/LFw2OANkR9e zlb0gMMhOR1mwWok3xwMl3gOAucEj38= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=pass header.d=columbia.edu header.s=pps01 header.b=DkA7DbxK; spf=pass (imf10.hostedemail.com: domain of tz2294@columbia.edu designates 148.163.135.74 as permitted sender) smtp.mailfrom=tz2294@columbia.edu; dmarc=pass (policy=none) header.from=columbia.edu ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1749237332; a=rsa-sha256; cv=none; b=Wzmbs8zsGCNrO72FFca9Cht3kHNLSueeIzY2QGBNnqhgFWSPqA4cPaxBpaKbbkmXLsfi9I MetOfJKL+iIDf7KlVTpM+XHSEDPpdsjdxu0C001dCnKmk+z1uz+bORe5DYj7C6mR9OodHy SL6c9p2kfsXjQWURvtN6IUgMvPAMJMk= Received: from pps.filterd (m0167069.ppops.net [127.0.0.1]) by mx0a-00364e01.pphosted.com (8.18.1.2/8.18.1.2) with ESMTP id 556JFF3l017211 for ; Fri, 6 Jun 2025 15:15:30 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=columbia.edu; h=cc : content-transfer-encoding : content-type : date : from : in-reply-to : message-id : mime-version : references : subject : to; s=pps01; bh=hxKpvIwDJev2AQJKrOOsefY7R3fXf+i39zjL9smzWlg=; b=DkA7DbxKWkuSHI4iA1MT142Cpjb6/8TlBCIIakYVq0CquCP/OsqASktksi65uhVS3R0K pYAf0AWDlurGLVY0A7dax6S2OkNvYHys/MxWBNvZt5WywemKs+i2cp9KKyyX57XalUIB Z1wbzFseZeI904Snaxa0hDVP8qvYuw1r5I16/pG/SBkvCw0JxaURlW15Vmbafv8xFP9L aowr3D/GGER2+HZChR4zQDlQ5/fF8cCKxYAxA7ziPaETHJyOJZx+ckqWd+YNunLjeg6g LcvHQ8FAnOnAsP8auXLJCNtclMht8N8djMRGW4Ws17QR+WWlgUqS6xiy0vg9Tkz+yh9T oQ== Received: from mail-yw1-f199.google.com (mail-yw1-f199.google.com [209.85.128.199]) by mx0a-00364e01.pphosted.com (PPS) with ESMTPS id 471ethm164-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Fri, 06 Jun 2025 15:15:29 -0400 Received: by mail-yw1-f199.google.com with SMTP id 00721157ae682-70e735c7857so31559227b3.3 for ; Fri, 06 Jun 2025 12:15:29 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1749237328; x=1749842128; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=hxKpvIwDJev2AQJKrOOsefY7R3fXf+i39zjL9smzWlg=; b=PFinCH2O9YXoz54C735japnkG1p++z4ebT20Eooddms+PAop21WKKiFLtacTvvEE8B 57t/BlWdtYchWyYVH9drOyKh/lM8bt++Y5iF1m6yViyzGmKWcrjY3EPmvBTVZA5S8OfQ XaadQXN6QpdoYFOqVIgZJF0sl4fQc6N1pvc9SETWmDhAH30VbZxZWcQbrzSODgADeudX 9KOPpNYcL96pdKXvd2tAuEon6sze/rGL+3AwgMYvG5zAbCWzzxs5lWQI4F28ZOhxTiv0 BnM9C3W2m+jarGm6LZKjBF3SmaVEjqkHJH8hUaesmQAEmYo3EHtUgXrE4+0t8v+B9O++ gfZg== X-Forwarded-Encrypted: i=1; AJvYcCXiMCjGHFYKTSJsEUArR7ply6bks+djQNlPlcp4R1++MUEJSsvtZU+es5YI4+R0A8Xl3Cw/ZfNorA==@kvack.org X-Gm-Message-State: AOJu0YyGnIjh3PPW52p2xaGML24LbFtAaueKavXfbO20V7wLTBdWngxW JStB8SUZMjOcyDyclGgg4DKANW9StbiQ6sqlHC7P/Gp4jjT9nFH7fVDg4jyLDCpHgqWM4+vvb6K w3EufpyPjp+nLsjciGoYXuc697JSZA8vKxmBhFLWIwUa3oUBgXQmqk6903YRd5l8/fS3xypuxKn P0P0/m3cea9AA5XwdTP3w7meo= X-Gm-Gg: ASbGncvc9NUFRuMS3l4guueoYPGqfgRJoxXJR7pQS19JvfPZdri8/k0xxHKmxO0G7xo 71aQJPYYex1PkbNZcR3UewkMDVxnhEEm71XVNoh9Rnuivcqlks0JTCToo5q988imxtwDsWZtzPG TCeSjJ X-Received: by 2002:a05:690c:360e:b0:70d:f3bb:a731 with SMTP id 00721157ae682-710f76949a7mr61381237b3.9.1749237328271; Fri, 06 Jun 2025 12:15:28 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGmh5c+UyPtFHTyhFmv9SKnRfaGxEIhGfyJzFKAkpNJdzUL5OS8y0tgPWOcR4UTikcCpHWRgcH8NmKHKIpVeQg= X-Received: by 2002:a05:690c:360e:b0:70d:f3bb:a731 with SMTP id 00721157ae682-710f76949a7mr61380767b3.9.1749237327889; Fri, 06 Jun 2025 12:15:27 -0700 (PDT) MIME-Version: 1.0 References: <20250603-uffd-fixes-v1-0-9c638c73f047@columbia.edu> <20250603-uffd-fixes-v1-2-9c638c73f047@columbia.edu> <84cf5418-42e9-4ec5-bd87-17ba91995c47@redhat.com> In-Reply-To: From: Tal Zussman Date: Fri, 6 Jun 2025 15:15:17 -0400 X-Gm-Features: AX0GCFv-LebVJckbZYYmiOxBhz5geAlpM1m_LD3eRjbOgJZYzDANJjo8J0v__W4 Message-ID: Subject: Re: [PATCH 2/3] userfaultfd: prevent unregistering VMAs through a different userfaultfd To: Peter Xu Cc: David Hildenbrand , Andrew Morton , "Jason A. Donenfeld" , Alexander Viro , Christian Brauner , Jan Kara , Andrea Arcangeli , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Proofpoint-GUID: z2MvSfNaQAIz7BlR_bmnDlEPDCG77_iZ X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNjA2MDE2NiBTYWx0ZWRfX4D8IvYAgdEaW T3XUwfNEsTK2AhQxC01f+KSxOMpIjuNCu+HyUykYMSy6Jfa5tFZMd1ZIdebJuYb/qcNc3vMTr1s BxEMb5Pbry0wdQ8u68HaXKRKFrIMvH3c9MihsEpqT1z/nu6ZI8IISiyDgRzqBSfwmqHJlM+bick 6qTiZPRhcDkHF5/0yOyMmday/zrNCy7j8b1lerwmaU/DxQGi0ONefTdzkBLNP/cIskjOS1dwgFh 9WWdtm6PR78uB1WRreywOcQdE7ppJm7pYCI/w5L4ZtS5wpRSjE7ru1emsnIBKDOyaiOhDXsCSAb xXiUVA4s2r5ohirmMy+/wdGkilHCq/Q/j/KYa2Ab9Hv9vHKkh9AlfxTzPTvm+wZMXM49ydMdsMV s6R0Zi7m X-Proofpoint-ORIG-GUID: z2MvSfNaQAIz7BlR_bmnDlEPDCG77_iZ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.0.736,FMLib:17.12.80.40 definitions=2025-06-06_07,2025-06-05_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 malwarescore=0 impostorscore=0 suspectscore=0 lowpriorityscore=10 phishscore=0 bulkscore=10 adultscore=0 priorityscore=1501 clxscore=1015 mlxscore=0 mlxlogscore=716 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2505160000 definitions=main-2506060166 X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: BD598C0009 X-Stat-Signature: 5aq1odtg6gjnstiogsrgxuhk45f3sa1a X-Rspam-User: X-HE-Tag: 1749237331-512885 X-HE-Meta: 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 7aQEDcJJ lWuM5LgmZBUAacEpoRBB9cQ4ZcuiUHrpWTqqPmbPR4uXr8bApwtQZ3lraZyJI73t9GYjxWu73gzNeunl9IWeMhaWMbRXGb/JO4C6HS1gfyUI8aHJtxtFrJHETqXJhXwlXt7XjbXEA4I8gc9cb0VZUqYWFxwyKPeOj46bvFAeZ8xeWLR9CEsZfOoTZWlv3A4xe9N4J/ZJ5o6PrIljver1Z+kLoKZ4rzrHzmWwz0k7qTclBGmrPlQIyetSZoIHy4/3/Gx/6rEl4RPiR4lEGMUmstsyap5gdnxZqDz2sf0GZYhkGw4ZWTTzXJ3Yai8uPpBAwCRR3 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Jun 6, 2025 at 9:25=E2=80=AFAM Peter Xu wrote: > On Thu, Jun 05, 2025 at 05:11:53PM -0400, Tal Zussman wrote: > > > > As I mentioned in my response to James, it seems like the existing beha= vior > > is broken as well, due to the following in in userfaultfd_unregister(): > > > > if (!vma_can_userfault(cur, cur->vm_flags, wp_async)) > > goto out_unlock; > > > > where wp_async is derived from ctx, not cur. > > > > Pasting here: > > > > This also seems to indicate that the current behavior is broken and may= reject > > unregistering some VMAs incorrectly. For example, a file-backed VMA reg= istered > > with `wp_async` and UFFD_WP cannot be unregistered through a VMA that d= oes not > > have `wp_async` set. > > This is true. Meanwhile it seems untrivial to fix the flag alone with th= e > prior per-vma loop to check compatibility. We could drop the prior check > but then it slightly breaks the abi in another way.. > > Then let's go with the change to see our luck. > > Could you mention more things when repost in the commit log? (1) wp_asyn= c > bug, (2) explicitly mention that this is a slight ABI change, and (3) not > needed to backport to stable. Will do! > Thanks, > > -- > Peter Xu >