From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45782 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726312AbgJGTA1 (ORCPT ); Wed, 7 Oct 2020 15:00:27 -0400 Received: from mail-qv1-xf42.google.com (mail-qv1-xf42.google.com [IPv6:2607:f8b0:4864:20::f42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CE2FDC0613D3 for ; Wed, 7 Oct 2020 12:00:25 -0700 (PDT) Received: by mail-qv1-xf42.google.com with SMTP id w5so1771609qvn.12 for ; Wed, 07 Oct 2020 12:00:25 -0700 (PDT) Date: Wed, 7 Oct 2020 16:00:23 -0300 From: Jason Gunthorpe Subject: Re: [PATCH 11/13] mm: add unsafe_follow_pfn Message-ID: <20201007190023.GA5177@ziepe.ca> References: <20201007164426.1812530-1-daniel.vetter@ffwll.ch> <20201007164426.1812530-12-daniel.vetter@ffwll.ch> <20201007173647.GW5177@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: List-ID: To: Daniel Vetter Cc: DRI Development , LKML , kvm@vger.kernel.org, Linux MM , Linux ARM , linux-samsung-soc , "open list:DMA BUFFER SHARING FRAMEWORK" , linux-s390@vger.kernel.org, Daniel Vetter , Kees Cook , Dan Williams , Andrew Morton , John Hubbard , =?utf-8?B?SsOpcsO0bWU=?= Glisse , Jan Kara On Wed, Oct 07, 2020 at 08:10:34PM +0200, Daniel Vetter wrote: > On Wed, Oct 7, 2020 at 7:36 PM Jason Gunthorpe wrote: > > > > On Wed, Oct 07, 2020 at 06:44:24PM +0200, Daniel Vetter wrote: > > > Way back it was a reasonable assumptions that iomem mappings never > > > change the pfn range they point at. But this has changed: > > > > > > - gpu drivers dynamically manage their memory nowadays, invalidating > > > ptes with unmap_mapping_range when buffers get moved > > > > > > - contiguous dma allocations have moved from dedicated carvetouts to > > > cma regions. This means if we miss the unmap the pfn might contain > > > pagecache or anon memory (well anything allocated with GFP_MOVEABLE) > > > > > > - even /dev/mem now invalidates mappings when the kernel requests that > > > iomem region when CONFIG_IO_STRICT_DEVMEM is set, see 3234ac664a87 > > > ("/dev/mem: Revoke mappings when a driver claims the region") > > > > > > Accessing pfns obtained from ptes without holding all the locks is > > > therefore no longer a good idea. > > > > > > Unfortunately there's some users where this is not fixable (like v4l > > > userptr of iomem mappings) or involves a pile of work (vfio type1 > > > iommu). For now annotate these as unsafe and splat appropriately. > > > > > > This patch adds an unsafe_follow_pfn, which later patches will then > > > roll out to all appropriate places. > > > > > > Signed-off-by: Daniel Vetter > > > Cc: Jason Gunthorpe > > > Cc: Kees Cook > > > Cc: Dan Williams > > > Cc: Andrew Morton > > > Cc: John Hubbard > > > Cc: Jérôme Glisse > > > Cc: Jan Kara > > > Cc: Dan Williams > > > Cc: linux-mm@kvack.org > > > Cc: linux-arm-kernel@lists.infradead.org > > > Cc: linux-samsung-soc@vger.kernel.org > > > Cc: linux-media@vger.kernel.org > > > Cc: kvm@vger.kernel.org > > > include/linux/mm.h | 2 ++ > > > mm/memory.c | 32 +++++++++++++++++++++++++++++++- > > > mm/nommu.c | 17 +++++++++++++++++ > > > security/Kconfig | 13 +++++++++++++ > > > 4 files changed, 63 insertions(+), 1 deletion(-) > > > > Makes sense to me. > > > > I wonder if we could change the original follow_pfn to require the > > ptep and then lockdep_assert_held() it against the page table lock? > > The safe variant with the pagetable lock is follow_pte_pmd. The only > way to make follow_pfn safe is if you have an mmu notifier and > corresponding retry logic. That is not covered by lockdep (it would > splat if we annotate the retry side), so I'm not sure how you'd check > for that? Right OK. > Checking for ptep lock doesn't work here, since the one leftover safe > user of this (kvm) doesn't need that at all, because it has the mmu > notifier. Ah, so a better name and/or function kdoc for follow_pfn is probably a good iead in this patch as well. > So I think we're as good as it gets, since I really have no idea how > to make sure follow_pfn callers do have an mmu notifier registered. Yah, can't be done. Most mmu notifier users should be using hmm_range_fault anyhow, kvm is really very special here. > I've followed the few other CONFIG_STRICT_FOO I've seen, which are all > explicit enables and default to "do not break uapi, damn the > (security) bugs". Which is I think how this should be done. It is in > the security section though, so hopefully competent distros will > enable this all. I thought the strict ones were more general and less clear security worries, not bugs like this. This is "allow a user triggerable use after free bug to exist in the kernel" Jason 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=-7.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,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 97654C4363C for ; Wed, 7 Oct 2020 19:02:08 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 CEE7E2168B for ; Wed, 7 Oct 2020 19:02:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="y2VRYbwO"; dkim=fail reason="signature verification failed" (2048-bit key) header.d=ziepe.ca header.i=@ziepe.ca header.b="cMpNZVJG" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CEE7E2168B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ziepe.ca Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=sUbnuS1D6fGHhggGwoACTX3v0pKC0Te9+bVaH6Tf69I=; b=y2VRYbwO0989Llne2J7t1fHTA OQsZUzi2OF4vtLeOYoPs2Oi656ToEFUERCU1ISdj8qOT4VKqgNoX/s7NRsnOhw1i8Rkh6TdjTm1AP ipSj24vWSdJd9iD+8S3KP0312WKDU7ALDg55IdSnJz8Kcm/0b2pn/wYnsFGWTq5UCEjIkt+5ZIap3 6usDbUjZTHNwiyRyVnzEc7HYt1/NKnC2R7wAiq1rBKWko5AU+0jKrwAn77kITnGwOV0P5jmstVkgn LqNDvMJZrfOgXRPIStbJ85DrO4yHXhqrai+pKzlLR6TUFCqso+vK9rOB6Hk+LYSwsBHL8f5s2Vet4 Ue2mkpBnA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kQEfu-0000X4-I5; Wed, 07 Oct 2020 19:00:30 +0000 Received: from mail-qv1-xf41.google.com ([2607:f8b0:4864:20::f41]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kQEfr-0000W4-6Y for linux-arm-kernel@lists.infradead.org; Wed, 07 Oct 2020 19:00:28 +0000 Received: by mail-qv1-xf41.google.com with SMTP id q10so1793058qvs.1 for ; Wed, 07 Oct 2020 12:00:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to; bh=gwCbc+E55rt8fvg0Z5RrVkUNpQiUldF+rgqAtNMU+jY=; b=cMpNZVJG4K3eU3P6Jrd5CX0FOMJ/Il/vK4/7K8PoeJK7lgtOlsvjUxgy6GDWgBQ9D2 Aw5daoxRX/jrMpwNlaXAoNbojcae9A3GOXghtCpRVV9HiqHG68GEdYZUDKJSzv88i+3p aFkcGAX3Swzr2MMkwPQxIHr1Vh0HtpCatuWCeA2XXODcHpk/xTpMM82sPz7LoWoj7YYW Luz6GqqQzWzkcXY5HEYy6sj4zsu7Bc3sA+CDzGGX0SAXYkf0OGAbHVxxlJGYn7JBpuJm 7XOCU2H2Wb2aAXJ06fg5h12CT15LqHGmR1WX6xifpDWK1MH5EARIEabM4b4xkoRgWTA0 GO+A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=gwCbc+E55rt8fvg0Z5RrVkUNpQiUldF+rgqAtNMU+jY=; b=leZj/2IVmXveVGwZgUmvDA2cA6IcCALhTshe5LbNPzFYLULtRvSUROEukxd1DYo9fU cLsgjTNQn+VZ16dPsl6ZdKw0a6FfI6pclFWv6Cfm77i7mv68k1NmNzOaCutzzBY+My/q th5NDwNTwMqn+YvPOd/rv8xhY87qynzrVzPpxGdj4thu1d87G4Hx2MPuFesfDiKZTHbz IlmonlaOhw+doKwoj/5BqRPY2M0I9cY4I7yG0zfR2OxsanxsMg8Fkvf6U9PAO3MH89KT WSkDes9w4HD2d/8Jdc0rzBwZPf0LA2YCRV2Dj7DL2KMCECDYvIeRoRtTDdWSwbuy3LL1 CFow== X-Gm-Message-State: AOAM530cvDiiTnu1XsH+0Pt/1y7yAOe5e2YfeIzjkPopCWgr8Hdao1g6 C9GqwoD37NBmFmccdZNjaFf6dg== X-Google-Smtp-Source: ABdhPJzTPvAeI7la8FWGJoa8jqCaN28XQwmJorKlewk43J8Zj2TVezuTxCVG7tggprHbo9uup+dLjQ== X-Received: by 2002:a0c:9d03:: with SMTP id m3mr4454155qvf.54.1602097224984; Wed, 07 Oct 2020 12:00:24 -0700 (PDT) Received: from ziepe.ca (hlfxns017vw-156-34-48-30.dhcp-dynamic.fibreop.ns.bellaliant.net. [156.34.48.30]) by smtp.gmail.com with ESMTPSA id v65sm2143675qkb.88.2020.10.07.12.00.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 07 Oct 2020 12:00:24 -0700 (PDT) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1kQEfn-001EwU-Q3; Wed, 07 Oct 2020 16:00:23 -0300 Date: Wed, 7 Oct 2020 16:00:23 -0300 From: Jason Gunthorpe To: Daniel Vetter Subject: Re: [PATCH 11/13] mm: add unsafe_follow_pfn Message-ID: <20201007190023.GA5177@ziepe.ca> References: <20201007164426.1812530-1-daniel.vetter@ffwll.ch> <20201007164426.1812530-12-daniel.vetter@ffwll.ch> <20201007173647.GW5177@ziepe.ca> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201007_150027_272667_2EFCC36A X-CRM114-Status: GOOD ( 33.75 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-s390@vger.kernel.org, linux-samsung-soc , Jan Kara , Kees Cook , kvm@vger.kernel.org, John Hubbard , LKML , DRI Development , Linux MM , =?utf-8?B?SsOpcsO0bWU=?= Glisse , Daniel Vetter , Dan Williams , Andrew Morton , Linux ARM , "open list:DMA BUFFER SHARING FRAMEWORK" Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org T24gV2VkLCBPY3QgMDcsIDIwMjAgYXQgMDg6MTA6MzRQTSArMDIwMCwgRGFuaWVsIFZldHRlciB3 cm90ZToKPiBPbiBXZWQsIE9jdCA3LCAyMDIwIGF0IDc6MzYgUE0gSmFzb24gR3VudGhvcnBlIDxq Z2dAemllcGUuY2E+IHdyb3RlOgo+ID4KPiA+IE9uIFdlZCwgT2N0IDA3LCAyMDIwIGF0IDA2OjQ0 OjI0UE0gKzAyMDAsIERhbmllbCBWZXR0ZXIgd3JvdGU6Cj4gPiA+IFdheSBiYWNrIGl0IHdhcyBh IHJlYXNvbmFibGUgYXNzdW1wdGlvbnMgdGhhdCBpb21lbSBtYXBwaW5ncyBuZXZlcgo+ID4gPiBj aGFuZ2UgdGhlIHBmbiByYW5nZSB0aGV5IHBvaW50IGF0LiBCdXQgdGhpcyBoYXMgY2hhbmdlZDoK 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