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=-11.4 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=no 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 50CC9C433DF for ; Thu, 20 Aug 2020 21:45:42 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 15A9F2075E for ; Thu, 20 Aug 2020 21:45:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="uYLB9g0/" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 15A9F2075E Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 872966B0029; Thu, 20 Aug 2020 17:45:41 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7FD1D6B002A; Thu, 20 Aug 2020 17:45:41 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6C40F6B002B; Thu, 20 Aug 2020 17:45:41 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0086.hostedemail.com [216.40.44.86]) by kanga.kvack.org (Postfix) with ESMTP id 5347D6B0029 for ; Thu, 20 Aug 2020 17:45:41 -0400 (EDT) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 16DDC181AEF09 for ; Thu, 20 Aug 2020 21:45:41 +0000 (UTC) X-FDA: 77172279282.01.part61_5c1671927033 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin01.hostedemail.com (Postfix) with ESMTP id CDC851004EC56 for ; Thu, 20 Aug 2020 21:45:40 +0000 (UTC) X-HE-Tag: part61_5c1671927033 X-Filterd-Recvd-Size: 5876 Received: from mail-ua1-f65.google.com (mail-ua1-f65.google.com [209.85.222.65]) by imf30.hostedemail.com (Postfix) with ESMTP for ; Thu, 20 Aug 2020 21:45:40 +0000 (UTC) Received: by mail-ua1-f65.google.com with SMTP id u15so1028707uau.10 for ; Thu, 20 Aug 2020 14:45:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=oiClaaiCtni3XCvYzCk2PHN22B0uQ/pdVdmtO+hfQvo=; b=uYLB9g0/x5lDS74dBvzkXpAwd/t/adN7kBz0Mcpj5dW3k7Gc/IpMgj+O31wzSrRg47 tJNcLUrDI9goLr+k+lUPQnTpEaoPtk3b1dOMxRdQ5vaoEak3agI4umQYqq3TbSoGakHQ 6ifF7uPxXyO/8TuKxexDp39A6YE25NMWeKVBX2zSTr31mM3/Lh+yZrfliFcpnYLe8+Hf 3BlgTKs0UX6jPN5l4hoXd0Hea1pNOx6XDl1Y6aI7ap9+OZjEFBr8tHklju9x8z7vwyjR qGYc2Uaz4pvfu4aVbrIZsME9ftqgIa4FQqRoVqjhLN4H7vkf8In7jn4EiGxleg5pV2YA SUZA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=oiClaaiCtni3XCvYzCk2PHN22B0uQ/pdVdmtO+hfQvo=; b=sBClroHNpa+7l0vtdpwwNPtWlgg9kTNdiWd28jcFGcHmblAx2rqN48E+Mk4lID6wdK uJsY8ntFuSBXR/mVYWWQMYxkiV0Su/hN0u4MuJoQJgiAPPLzd6j1EODty/uOnolix1Pl +NviaYTbzGoJjZiQrVwuih/1dplRgP8VMBFC/EC3iSA4iRP9wqCBihZNjBZL67C+v/qo hyq1ENeiB8HEqg74eczQJbftp4t5FrLqJJvwDFty0BnGldSPd5p6pM7QU7kY/NbPA8Ct qzcALRpI4gDgZf369RFRRinz4kTZ9QLpTC87HaTpco/u2BvJM6SCtL+Yxdzj+RKFPhEE sIZg== X-Gm-Message-State: AOAM530sMHhfdw8CujPh1O2slrOtlI9kn5+TRII6cwKmsUdRGxfz3W/k IGScSYyOKwu56WH4ynknxFhqF/XJ0InnB9PupxsDbQ== X-Google-Smtp-Source: ABdhPJxNvaxpvoez0typs4Xl835A4xzHQuKDeLLi34Dp1cilB98RirSWG4H2gMew174BnbKDFq0UpKhsK9VAY/kuqms= X-Received: by 2002:ab0:70b6:: with SMTP id q22mr528958ual.66.1597959939254; Thu, 20 Aug 2020 14:45:39 -0700 (PDT) MIME-Version: 1.0 References: <20200819141650.7462-1-sumit.semwal@linaro.org> <20200819141650.7462-3-sumit.semwal@linaro.org> <20200820214003.GR2074@grain> In-Reply-To: <20200820214003.GR2074@grain> From: Colin Cross Date: Thu, 20 Aug 2020 14:45:27 -0700 Message-ID: Subject: Re: [PATCH v5 2/2] mm: add a field to store names for private anonymous memory To: Cyrill Gorcunov Cc: Sumit Semwal , Andrew Morton , Linux-MM , lkml , Alexey Dobriyan , Jonathan Corbet , Mauro Carvalho Chehab , Kees Cook , Michal Hocko , Alexey Gladkov , Matthew Wilcox , Jason Gunthorpe , "Kirill A . Shutemov" , Michel Lespinasse , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Song Liu , Huang Ying , Vlastimil Babka , Yang Shi , chenqiwu , Mathieu Desnoyers , John Hubbard , Thomas Hellstrom , Mike Christie , Bart Van Assche , Amit Pundir , Thomas Gleixner , Christian Brauner , Daniel Jordan , Adrian Reber , Nicolas Viennot , Al Viro , Thomas Cedeno , linux-fsdevel@vger.kernel.org, Pekka Enberg , Dave Hansen , Peter Zijlstra , Ingo Molnar , Oleg Nesterov , "Eric W. Biederman" , Jan Glauber , John Stultz , Rob Landley , "Serge E. Hallyn" , David Rientjes , Hugh Dickins , Rik van Riel , Mel Gorman , Tang Chen , Robin Holt , Shaohua Li , Sasha Levin , Johannes Weiner , Minchan Kim Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: CDC851004EC56 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 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, Aug 20, 2020 at 2:40 PM Cyrill Gorcunov wrote: > > On Wed, Aug 19, 2020 at 07:46:50PM +0530, Sumit Semwal wrote: > ... > > Userspace can set the name for a region of memory by calling > > prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, start, len, (unsigned long)name); > > Setting the name to NULL clears it. > > > > The name is stored in a user pointer in the shared union in vm_area_struct > > that points to a null terminated string inside the user process. vmas > > that point to the same address and are otherwise mergeable will be merged, > > but vmas that point to equivalent strings at different addresses will not > > be merged. > ... > > Guys, could you please enlighen me, I don't understand -- we pass some > random user-space pointer and save it in vm_area_struct then in procfs > we treat it as "string" and print out? What prevents me to put some crap > here then unmap this pointer the kernel will cause page fault in procfs > output (in best scenario)? This is the same pattern used for /proc/pid/cmdline. acccess_remote_vm handles addresses in unmapped pages, it will return 0 if no bytes were readable.