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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 39122C4727E for ; Wed, 7 Oct 2020 14:09:10 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 49FEB206BE for ; Wed, 7 Oct 2020 14:09:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=ffwll.ch header.i=@ffwll.ch header.b="B4PLpbur" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 49FEB206BE Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ffwll.ch Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 4ECDE6E8F2; Wed, 7 Oct 2020 14:09:08 +0000 (UTC) Received: from mail-oo1-xc43.google.com (mail-oo1-xc43.google.com [IPv6:2607:f8b0:4864:20::c43]) by gabe.freedesktop.org (Postfix) with ESMTPS id F1B0A6E8F2 for ; Wed, 7 Oct 2020 14:09:06 +0000 (UTC) Received: by mail-oo1-xc43.google.com with SMTP id w7so645569oow.7 for ; Wed, 07 Oct 2020 07:09:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=F5NtGNV4UXqtob/Dy8Wfu3ZnV2YG7ZTF8Dz7SU/MRuA=; b=B4PLpburyCDHIfOP25bhhP5r9tO+rxb3oufGcc1bi7vBgcrdV+TGTIhDv3iLTdW/e3 oIr3r8n5BHeowIpG4G2PtYVK0pjnuwRKRa5QxkdhF8GSBqXvOSF2jkGXbTBeRECcAImq DchpU/Y/YQ235XjHuiSdLX0FDwNJ1FnUf5B4s= 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=F5NtGNV4UXqtob/Dy8Wfu3ZnV2YG7ZTF8Dz7SU/MRuA=; b=CW8iki0uGEhCJc+ZUeVzSJZh9r17IsiyKpzFMXzLJf6qDxS0WZOFplfjeo84WlnmfF Ls7xV9RE1OOAiPHpWj5F4u1PDjothB0hD7VLiqQUL2K/bV0iMbSNoGTfGaPDv5u+RFhC fKVIrpFgd/OCPxC4up7M4J8+H2baoyi/QKou+OM5aoV41MXEYz5GQDJFOtS/p6KCUZI3 N1/fTuvBQZNCfzZoeIBZUqlzLSC7WwA/UCtNzmkOEken1p4ra3TNA/bjjEG/Q294yP24 C4FG5Plc70hD35QpJxaXu4ExlmZ4iSowz+r/f6dnqI4O8bbjOxIQLSlGNwJnyXJSug7M XALA== X-Gm-Message-State: AOAM5321wxpXFlxDPYqGCkuISV8B2tbFYg+b88eXhIHRdTi208wOH6SX 5wp+nlSku4b5+RVdcvLNkF/tWhcbAR7bSJsqYPqCSw== X-Google-Smtp-Source: ABdhPJw2MxOMsCCHLuA0B2aXMY51PcMyywibrKXkCKUzUw6tJNpIcvbizXHrg3fACcDmzezaL+tQ7uy44dIyRAnAIS8= X-Received: by 2002:a4a:e592:: with SMTP id o18mr2184941oov.28.1602079746086; Wed, 07 Oct 2020 07:09:06 -0700 (PDT) MIME-Version: 1.0 References: <20201002233118.GM9916@ziepe.ca> <725819e9-4f07-3f04-08f8-b6180406b339@samsung.com> <20201007124409.GN5177@ziepe.ca> <20201007130610.GP5177@ziepe.ca> In-Reply-To: From: Daniel Vetter Date: Wed, 7 Oct 2020 16:08:54 +0200 Message-ID: Subject: Re: [PATCH 2/2] mm/frame-vec: use FOLL_LONGTERM To: Tomasz Figa X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-samsung-soc , Jan Kara , Joonyoung Shim , Pawel Osciak , Linux MM , John Hubbard , Seung-Woo Kim , LKML , DRI Development , Kyungmin Park , Jason Gunthorpe , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Daniel Vetter , Andrew Morton , "open list:DMA BUFFER SHARING FRAMEWORK" , Dan Williams , Linux ARM , Marek Szyprowski Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Wed, Oct 7, 2020 at 3:34 PM Tomasz Figa wrote: > > On Wed, Oct 7, 2020 at 3:06 PM Jason Gunthorpe wrote: > > > > On Wed, Oct 07, 2020 at 02:58:33PM +0200, Daniel Vetter wrote: > > > On Wed, Oct 7, 2020 at 2:48 PM Tomasz Figa wrote: > > > > > > > > On Wed, Oct 7, 2020 at 2:44 PM Jason Gunthorpe wrote: > > > > > > > > > > On Wed, Oct 07, 2020 at 02:33:56PM +0200, Marek Szyprowski wrote: > > > > > > Well, it was in vb2_get_vma() function, but now I see that it has been > > > > > > lost in fb639eb39154 and 6690c8c78c74 some time ago... > > > > > > > > > > There is no guarentee that holding a get on the file says anthing > > > > > about the VMA. This needed to check that the file was some special > > > > > kind of file that promised the VMA layout and file lifetime are > > > > > connected. > > > > > > > > > > Also, cloning a VMA outside the mm world is just really bad. That > > > > > would screw up many assumptions the drivers make. > > > > > > > > > > If it is all obsolete I say we hide it behind a default n config > > > > > symbol and taint the kernel if anything uses it. > > > > > > > > > > Add a big comment above the follow_pfn to warn others away from this > > > > > code. > > > > > > > > Sadly it's just verbally declared as deprecated and not formally noted > > > > anyway. There are a lot of userspace applications relying on user > > > > pointer support. > > > > > > userptr can stay, it's the userptr abuse for zerocpy buffer sharing > > > which doesn't work anymore. At least without major surgery (you'd need > > > an mmu notifier to zap mappings and recreate them, and that pretty > > > much breaks the v4l model of preallocating all buffers to make sure we > > > never underflow the buffer queue). And static mappings are not coming > > > back I think, we'll go ever more into the direction of dynamic > > > mappings and moving stuff around as needed. > > > > Right, and to be clear, the last time I saw a security flaw of this > > magnitude from a subsystem badly mis-designing itself, Linus's > > knee-jerk reaction was to propose to remove the whole subsystem. > > > > Please don't take status-quo as acceptable, V4L community has to work > > to resolve this, uABI breakage or not. The follow_pfn related code > > must be compiled out of normal distro kernel builds. > > I think the userptr zero-copy hack should be able to go away indeed, > given that we now have CMA that allows having carveouts backed by > struct pages and having the memory represented as DMA-buf normally. Not sure whether there's a confusion here: dma-buf supports memory not backed by struct page. > How about the regular userptr use case, though? > > The existing code resolves the user pointer into pages by following > the get_vaddr_frames() -> frame_vector_to_pages() -> > sg_alloc_table_from_pages() / vm_map_ram() approach. > get_vaddr_frames() seems to use pin_user_pages() behind the scenes if > the vma is not an IO or a PFNMAP, falling back to follow_pfn() > otherwise. Yeah pin_user_pages is fine, it's just the VM_IO | VM_PFNMAP vma that don't work. > > Is your intention to drop get_vaddr_frames() or we could still keep > using it and if vec->is_pfns is true: > a) if CONFIG_VIDEO_LEGACY_PFN_USERPTR is set, taint the kernel > b) otherwise just undo and fail? I'm typing that patch series (plus a pile more) right now. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel