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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5EA64C433EF for ; Thu, 7 Oct 2021 18:50:23 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id ED39C61130 for ; Thu, 7 Oct 2021 18:50:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org ED39C61130 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 59752900002; Thu, 7 Oct 2021 14:50:22 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5200E6B0071; Thu, 7 Oct 2021 14:50:22 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3E6D7900002; Thu, 7 Oct 2021 14:50:22 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0176.hostedemail.com [216.40.44.176]) by kanga.kvack.org (Postfix) with ESMTP id 2CA376B006C for ; Thu, 7 Oct 2021 14:50:22 -0400 (EDT) Received: from smtpin12.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id CD49332332 for ; Thu, 7 Oct 2021 18:50:21 +0000 (UTC) X-FDA: 78670531842.12.5FAA25D Received: from mail-yb1-f171.google.com (mail-yb1-f171.google.com [209.85.219.171]) by imf04.hostedemail.com (Postfix) with ESMTP id 7D43A5001535 for ; Thu, 7 Oct 2021 18:50:21 +0000 (UTC) Received: by mail-yb1-f171.google.com with SMTP id i84so15502400ybc.12 for ; Thu, 07 Oct 2021 11:50:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=E0+5wT+wrdMqcXbNJTk/9zibrUNlQPSrWQVNSFGRH0Q=; b=f+jqxJIJSLt5FZwMq8HxqaGUYxnqZd2XHM9BdnYqSOU2kuqNgIW8wdNJ+eIspkoDj7 Y9gcKeC/pYYgB7yyLLyYx+RB+VVGInIY8fY+l7ByRtsBh75EzVZLLHUx0s/JgAaUxjSx hGIwnJa6ufRLm2694PKbR8PkW8ggrSVSF19tXiQkNxjdPHqzGQENgGZtovh4JP3nyBmm km/ahg3AYuRK3xJ3BxULxSYwkGBP+AaFviZfQCvWKnwo6U4m7pnW6dL83ihp8vhP+OEn KjczJIjrhAJYXJHrPGk4lt9lhphV4v8E1sVoy0rsM5C4FRJOlgdvGR8HGAR7WauUTcVs gaxQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=E0+5wT+wrdMqcXbNJTk/9zibrUNlQPSrWQVNSFGRH0Q=; b=la5OszqhyIM2XoX7lQ3IKm6Gd1SDbqbXI2w+bP/c8GTUwf/C0sFRzcWBjEdzCmv+2H v2FmBTUwApAFzOlx8Rano0pPPWUWuLZ3ayE2moRhBZZ6QetVjSNeO5jneGhbNKgn4xCJ fvuSBiFr7bF8NqKpsWuCVsd8Chpn6P3j1eHY227h5Us4xQf0gCMG37r7ZPN71id92Uto 4new/2879z5htnyGABygPvZf3DC2QFeKfHHNYTRy1oz7/4Bh6f1jpdN2U8czzXjBHUXT Al1L1TTAdkfMIglrnDNr51hAL9P2oo4lp0NYemse3Yipsu+PuoSBdJrexhiW4DM2twUc 0kWA== X-Gm-Message-State: AOAM5310WoJXdwEnAXVXM7SflAA1wyEIGbydO4P6vEUiBGuaaW2B40Ia IQQuHDUCi0FBnCSqGIuRhA1j0sbDSXEJdTNKtA0K/Q== X-Google-Smtp-Source: ABdhPJwX3MSlqHYl/15/mb53bQi9n5NdlsFOxC7cfpcgUkjWDcfJbTPgeVDqsBWb3sDjKC8m87AdHD4J0DwOcD30v/I= X-Received: by 2002:a25:5b04:: with SMTP id p4mr6402702ybb.34.1633632620440; Thu, 07 Oct 2021 11:50:20 -0700 (PDT) MIME-Version: 1.0 References: <20211006175821.GA1941@duo.ucw.cz> <92cbfe3b-f3d1-a8e1-7eb9-bab735e782f6@rasmusvillemoes.dk> <20211007101527.GA26288@duo.ucw.cz> <202110071111.DF87B4EE3@keescook> In-Reply-To: <202110071111.DF87B4EE3@keescook> From: Suren Baghdasaryan Date: Thu, 7 Oct 2021 11:50:09 -0700 Message-ID: Subject: Re: [PATCH v10 3/3] mm: add anonymous vma name refcounting To: Kees Cook Cc: Michal Hocko , Pavel Machek , Rasmus Villemoes , David Hildenbrand , John Hubbard , Andrew Morton , Colin Cross , Sumit Semwal , Dave Hansen , Matthew Wilcox , "Kirill A . Shutemov" , Vlastimil Babka , Johannes Weiner , Jonathan Corbet , Al Viro , Randy Dunlap , Kalesh Singh , Peter Xu , rppt@kernel.org, Peter Zijlstra , Catalin Marinas , vincenzo.frascino@arm.com, =?UTF-8?B?Q2hpbndlbiBDaGFuZyAo5by16Yym5paHKQ==?= , Axel Rasmussen , Andrea Arcangeli , Jann Horn , apopple@nvidia.com, Yu Zhao , Will Deacon , fenghua.yu@intel.com, thunder.leizhen@huawei.com, Hugh Dickins , feng.tang@intel.com, Jason Gunthorpe , Roman Gushchin , Thomas Gleixner , krisman@collabora.com, Chris Hyser , Peter Collingbourne , "Eric W. Biederman" , Jens Axboe , legion@kernel.org, Rolf Eike Beer , Cyrill Gorcunov , Muchun Song , Viresh Kumar , Thomas Cedeno , sashal@kernel.org, cxfcosmos@gmail.com, LKML , linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm , kernel-team Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 7D43A5001535 X-Stat-Signature: r49ggajm3s6hab79eyre434d1cneuhju Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=f+jqxJIJ; spf=pass (imf04.hostedemail.com: domain of surenb@google.com designates 209.85.219.171 as permitted sender) smtp.mailfrom=surenb@google.com; dmarc=pass (policy=reject) header.from=google.com X-HE-Tag: 1633632621-495134 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: On Thu, Oct 7, 2021 at 11:13 AM Kees Cook wrote: > > On Thu, Oct 07, 2021 at 10:50:24AM -0700, Suren Baghdasaryan wrote: > > On Thu, Oct 7, 2021 at 10:31 AM Michal Hocko wrote: > > > > > > On Thu 07-10-21 09:58:02, Suren Baghdasaryan wrote: > > > > On Thu, Oct 7, 2021 at 9:40 AM Michal Hocko wrote: > > > > > > > > > > On Thu 07-10-21 09:04:09, Suren Baghdasaryan wrote: > > > > > > On Thu, Oct 7, 2021 at 3:15 AM Pavel Machek wrote: > > > > > > > > > > > > > > Hi! > > > > > > > > > > > > > > > >> Hmm, so the suggestion is to have some directory which contains files > > > > > > > > >> representing IDs, each containing the string name of the associated > > > > > > > > >> vma? Then let's say we are creating a new VMA and want to name it. We > > > > > > > > >> would have to scan that directory, check all files and see if any of > > > > > > > > >> them contain the name we want to reuse the same ID. > > > > > > > > > > > > > > > > > > I believe Pavel meant something as simple as > > > > > > > > > $ YOUR_FILE=$YOUR_IDS_DIR/my_string_name > > > > > > > > > $ touch $YOUR_FILE > > > > > > > > > $ stat -c %i $YOUR_FILE > > > > > > > > > > > > Ah, ok, now I understand the proposal. Thanks for the clarification! > > > > > > So, this would use filesystem as a directory for inode->name mappings. > > > > > > One rough edge for me is that the consumer would still need to parse > > > > > > /proc/$pid/maps and convert [anon:inode] into [anon:name] instead of > > > > > > just dumping the content for the user. Would it be acceptable if we > > > > > > require the ID provided by prctl() to always be a valid inode and > > > > > > show_map_vma() would do the inode-to-filename conversion when > > > > > > generating maps/smaps files? I know that inode->dentry is not > > > > > > one-to-one mapping but we can simply output the first dentry name. > > > > > > WDYT? > > > > > > > > > > No. You do not want to dictate any particular way of the mapping. The > > > > > above is just one way to do that without developing any actual mapping > > > > > yourself. You just use a filesystem for that. Kernel doesn't and > > > > > shouldn't understand the meaning of those numbers. It has no business in > > > > > that. > > > > > > > > > > In a way this would be pushing policy into the kernel. > > > > > > > > I can see your point. Any other ideas on how to prevent tools from > > > > doing this id-to-name conversion themselves? > > > > > > I really fail to understand why you really want to prevent them from that. > > > Really, the whole thing is just a cookie that kernel maintains for memory > > > mappings so that two parties can understand what the meaning of that > > > mapping is from a higher level. They both have to agree on the naming > > > but the kernel shouldn't dictate any specific convention because the > > > kernel _doesn't_ _care_. These things are not really anything actionable > > > for the kernel. It is just a metadata. > > > > The desire is for one of these two parties to be a human who can get > > the data and use it as is without additional conversions. > > /proc/$pid/maps could report FD numbers instead of pathnames, which > > could be converted to pathnames in userspace. However we do not do > > that because pathnames are more convenient for humans to identify a > > specific resource. Same logic applies here IMHO. > > Yes, please. It really seems like the folks that are interested in this > feature want strings. (I certainly do.) For those not interested in the > feature, it sounds like a CONFIG to keep it away would be sufficient. > Can we just move forward with that? Would love to if others are ok with this. > > -- > Kees Cook