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 F0377C54E65 for ; Thu, 22 May 2025 15:14:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8DEB06B008C; Thu, 22 May 2025 11:14:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8B5FA6B0092; Thu, 22 May 2025 11:14:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 77FB56B0093; Thu, 22 May 2025 11:14:55 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 583DA6B008C for ; Thu, 22 May 2025 11:14:55 -0400 (EDT) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id F1F911418AF for ; Thu, 22 May 2025 15:14:54 +0000 (UTC) X-FDA: 83470891308.07.DD92734 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf21.hostedemail.com (Postfix) with ESMTP id 5C0781C000F for ; Thu, 22 May 2025 15:14:52 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=iLuwmrYC; spf=pass (imf21.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=quarantine) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1747926892; 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=7JYMI7LYWgp6z3rQ/on+fV5hlUyIolqkmdUowSNe14M=; b=YrQMvxxcPIblS6YzEhOjkAJepjBNK+TAx3bzzC50uzAyXy2tymK/YfoELkYoR0fbUNuPzW T+h98l8fWnqXP/mlF+BDwbA8rg4ith7PyxT2euTyA702xU8eej9+YiupxfVWU/4B5B4N2T p7Mnvqgut6xZZb79eE76vzrGVmOh17s= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1747926892; a=rsa-sha256; cv=none; b=fl/G5MmS14us5fAsUNpkOww/uVfI+5WN9/PzfvSbAm0AGUaRJhRyBzXYRmqUT4/IaE+CCs MRTz1JqmLG/eZGK374MwKkACm6JaL6YnrfTHF2kbDhyalhOUQm8onWewJadTZGK6dtkP3v Rgek7Em6k2EE22wbz5g4fSvYkDNRRog= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=iLuwmrYC; spf=pass (imf21.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=quarantine) header.from=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1747926891; h=from:from: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:autocrypt:autocrypt; bh=7JYMI7LYWgp6z3rQ/on+fV5hlUyIolqkmdUowSNe14M=; b=iLuwmrYCLU3kgwP/evKsYLlkeIQJf8PMsuS0WHRB78UGFZdWhN6I5C4oke9a25xBU/m99O C41JJ6zTgPsAtrPD3i0Md7JqJBJE9WNuQiwm+5eEVrpdVF5VgILJdqX98iYLmUIZXUlVVA 7ZiWtm+ApkOmHQZWfqX/z9vJoUQDPrE= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-581-v5ObFmM-M-2SGrXSm6h7vA-1; Thu, 22 May 2025 11:14:48 -0400 X-MC-Unique: v5ObFmM-M-2SGrXSm6h7vA-1 X-Mimecast-MFC-AGG-ID: v5ObFmM-M-2SGrXSm6h7vA_1747926887 Received: by mail-wm1-f70.google.com with SMTP id 5b1f17b1804b1-440667e7f92so42519695e9.3 for ; Thu, 22 May 2025 08:14:48 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1747926887; x=1748531687; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=7JYMI7LYWgp6z3rQ/on+fV5hlUyIolqkmdUowSNe14M=; b=xQf+H4DJfLVS2nIwMFnnJWedUybZrmpWA/wyjCzJvrI5q1NoYPWiYL0o1mp9lK2yG+ fLT/upPXXpwD9pYu9r5aacti9CBN22lk5AauRvubNxRj1n9VzVSn64/8dmGl9UCyBuDo rvzRHkBxAaP1AK43Y2E/iP1lvNltDqs6qkFy5o2UVA9+Jv7VgP4caOEOqbneuIZcSyof A1kC6DiMzuymfBUShpPAqv1HOXX51ca8iY5aZsQDHg2QFV/4bJVYZZO53uC30O+qTfQH OG4MKdrAQs1IVRbnyhXM5Y5+K/JlSc7yneDzUK+uL6OUXx2/lRkdyqp6JqM662I5kMcg Tz9w== X-Gm-Message-State: AOJu0YwpQuNQCXUUGTG0wF0yRz/cNRxzQy8NOJzTlq6kjY9YzZx9gTBm FoIJM1GKV2G2bNA8NSCQ2sGeCFGMf2ufj3OgQn/i0coR3XjM5h11xreIb7rNiTUJmOylc+K1sr1 BCAIK6R2e2JzZQEnlRIeOc0+gVgPJKQW4ruPkhHTb8GGFcHeVGzOm X-Gm-Gg: ASbGncvm7oFdu9r39nY+uRqtx+cnjuaVJKra1Ykk+Eo7t7i30T7+AbgWvoMNNeQf5gZ xVrsGUmX5xy+/vo7LdY0thbGqh3vTGBKKjZPgY5NB/ilm14XxmVQorlXuFSng6McHo4AnutZzGK 1Yhkdautqk3lOFSuNABXXXnIFCOy6839I+Fn32wSUMS5gAo66O0QVdmlHgHv/wR6++3nbLvW9cL v0tlCDUh4THwV+eYui7Rz6bad2F+QV+MLqy0vIvzOi9fLM9aih1FH1yHS7sFXezOqJQ15EnPoGo 2l3SuMrL2m3Y4AkM48cpveEm0jMInMaMpvcjwhcLLpgy0tTExLXjPlMJEExdXbINkaQxWwJTqzH Owd5Ry+eiowkFo94ou40bP1KOA4dJcDqzbFbZzlk= X-Received: by 2002:a05:600c:6487:b0:43c:fe15:41c9 with SMTP id 5b1f17b1804b1-442fd622e97mr229778875e9.9.1747926887342; Thu, 22 May 2025 08:14:47 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFTWXUQ6YSObrClsy1/nOpFkU0Ce4tkRLftf8Q8dErp8Umcz69taRh/uB+yKVOs/MofWoXCOQ== X-Received: by 2002:a05:600c:6487:b0:43c:fe15:41c9 with SMTP id 5b1f17b1804b1-442fd622e97mr229778535e9.9.1747926886903; Thu, 22 May 2025 08:14:46 -0700 (PDT) Received: from ?IPV6:2003:d8:2f22:2e00:6e71:238a:de9f:e396? (p200300d82f222e006e71238ade9fe396.dip0.t-ipconnect.de. [2003:d8:2f22:2e00:6e71:238a:de9f:e396]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-447f73d25b8sm113083635e9.17.2025.05.22.08.14.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 22 May 2025 08:14:46 -0700 (PDT) Message-ID: <13c5fe73-9e11-4465-b401-fc96a22dc5d1@redhat.com> Date: Thu, 22 May 2025 17:14:45 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH] mm/mmap: Fix uprobe anon page be overwritten when expanding vma during mremap To: Pu Lehui , mhiramat@kernel.org, oleg@redhat.com, peterz@infradead.org, akpm@linux-foundation.org, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, vbabka@suse.cz, jannh@google.com, pfalcato@suse.de Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, pulehui@huawei.com References: <20250521092503.3116340-1-pulehui@huaweicloud.com> <62b5ccf5-f1cd-43c2-b0bc-f542f40c5bdf@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: QbRg40hMZrs9GtzIWAQq_avq0ypWz7OwAzmek2kSr-g_1747926887 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 5C0781C000F X-Stat-Signature: u9wfwt3kknjftaxz4tk5bm5e6338juaw X-Rspam-User: X-HE-Tag: 1747926892-218863 X-HE-Meta: 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 5DZsxFH9 1n1Lf0kygjfd/DnGEnWNoMiNWjaSqc/qwiavulGU+xbxSBlBPWIKZsy3rZZeXbMy40U3bO7hsXbO1+1ZQGO6a50BL2+Skg1LDY749NrPvfptUBrUCLjKs2ap6nvghihBqOYNKg+3Cq6wISSzt6K7egiilwhBgHDCGCeLcMAB9pL7g2ytNQ4dq6HQRvxQtzCKhe3YcEreQXn5Le0k3yajAl7XD0jVPdOafs3ZQywrzW1H7GsQ6MpO7RzSCegugrpTIVThZD35wz4I6qeb7f9JVwy4aOvkOgTiWuVyvysd5FQSTjGmOMhBnVQiHO0vGjUa5Ep1llv76V3lsICihHZyOjaiIHHkJtY6xx6fuOM1r6hxLPDzcUxkCIglAw6FASyc+X6ZBt+GqXTp6V+fK7VULjrdkGlVsb3u7aueIRgIyp4GI4pC55N6Spss8UQaEZNKw0uEAgL/P13SJmkM= 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 22.05.25 16:37, Pu Lehui wrote: > > > On 2025/5/21 18:25, David Hildenbrand wrote: >> On 21.05.25 11:25, Pu Lehui wrote: >>> From: Pu Lehui >>> >>> We encountered a BUG alert triggered by Syzkaller as follows: >>>     BUG: Bad rss-counter state mm:00000000b4a60fca type:MM_ANONPAGES >>> val:1 >>> >>> And we can reproduce it with the following steps: >>> 1. register uprobe on file at zero offset >>> 2. mmap the file at zero offset: >>>     addr1 = mmap(NULL, 2 * 4096, PROT_NONE, MAP_PRIVATE, fd, 0); >> >> So, here we will install a uprobe. >> >>> 3. mremap part of vma1 to new vma2: >>>     addr2 = mremap(addr1, 4096, 2 * 4096, MREMAP_MAYMOVE); >> >> Okay, so we'll essentially move the uprobe as we mremap. >> >> >>> 4. mremap back to orig addr1: >>>     mremap(addr2, 4096, 4096, MREMAP_MAYMOVE | MREMAP_FIXED, addr1); >> >> And here, we would expect to move the uprobe again. >> >>> >>> In the step 3, the vma1 range [addr1, addr1 + 4096] will be remap to new >>> vma2 with range [addr2, addr2 + 8192], and remap uprobe anon page from >>> the vma1 to vma2, then unmap the vma1 range [addr1, addr1 + 4096]. >>> In tht step 4, the vma2 range [addr2, addr2 + 4096] will be remap back >>> to the addr range [addr1, addr1 + 4096]. Since the addr range [addr1 + >>> 4096, addr1 + 8192] still maps the file, it will take >>> vma_merge_new_range to merge these two addr ranges, and then do >>> uprobe_mmap in vma_complete. Since the merged vma pgoff is also zero >>> offset, it will install uprobe anon page to the merged vma. >> >> Oh, so we're installing the uprobe into the extended VMA before moving >> the page tables. > Yep! >> >> Gah. >> >>> However, the >>> upcomming move_page_tables step, which use set_pte_at to remap the vma2 >>> uprobe anon page to the merged vma, will over map the old uprobe anon >>> page in the merged vma, and lead the old uprobe anon page to be orphan. >> >> Right, when moving page tables we don't expect there to already be >> something from the uprobe code. >> >>> >>> Since the uprobe anon page will be remapped to the merged vma, we can >>> remove the unnecessary uprobe_mmap at merged vma, that is, do not >>> perform uprobe_mmap when there is no vma in the addr range to be >>> expaned. >> >> Hmmm, I'll have to think about other corner cases .... >> > looking forward to it I think, the rule is that we must not install a uprobe for the range that we will be actually moving the page tables for. So, for the range we're effectively moving (not the one we're extending). Because logically, the uprobe will be already handled by the existing page tables that we're moving. For the range we're extending, we must call uprobe handling code ... Alternatively, maybe we could call uprobe handling code after moving the page tables. We'd probably find that the uprobe is already installed and do nothing (so the theory :) ). ... if that would simplify anything. -- Cheers, David / dhildenb