From patchwork Tue Mar 16 15:33:01 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 12142517 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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 9F70BC43381 for ; Tue, 16 Mar 2021 15:33:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 77F71650EB for ; Tue, 16 Mar 2021 15:33:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237253AbhCPPd3 (ORCPT ); Tue, 16 Mar 2021 11:33:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36866 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238091AbhCPPdP (ORCPT ); Tue, 16 Mar 2021 11:33:15 -0400 Received: from mail-wm1-x336.google.com (mail-wm1-x336.google.com [IPv6:2a00:1450:4864:20::336]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A3329C061763 for ; Tue, 16 Mar 2021 08:33:14 -0700 (PDT) Received: by mail-wm1-x336.google.com with SMTP id g8so10349278wmd.4 for ; Tue, 16 Mar 2021 08:33:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=uUoRAMQqissgQiWNySzwnJOq0uwZjWt9LOiB5Qw/2Hk=; b=hFVpCvjsIApl22/AeCmNwSGg8SmuSyxqnnKJy4mQhR6BGEUcb+6lgx2UbMK4kBz1xN ULwJLX7V5bTAyN4GQ47VfP+7rqU5DByCia8kU6BZffozRa+USNu2ThKAIIOMLY56Z3rg BUM2+rVAKxKT7KfANn1fMFkXKRqHHvmbjo1v4= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=uUoRAMQqissgQiWNySzwnJOq0uwZjWt9LOiB5Qw/2Hk=; b=aq+Kz4v3Mj8sQW8iDs8l1oJqSLX74PitwKbQBKEPlBO8WqO1LwXaBK1d+dNfgI084d J3sGlKW7EbJzZSLLTpn2JHJjQGQuE94lRiLnuBPibotHRu7F56LOA9bXpyU5CU6GLKO2 b4L6/UDxBJSzdJaat/6+xYu2HDadhBJiBbDyFTx8GPHNMWzHz85MZ7Wwyf5PdniA2qgO qQYCxevlir0cmXhZNjL/I1d++IPaDVqu/N9aUYIPliTYj0ta1S927IZXTGwG49Gq3uet 2clafxJoYSp7ACf7+QWfY1wo1fkwnbzd4N40Csb0w4E8puHE1x/plfR/FeKZSBp8VZm0 YMcA== X-Gm-Message-State: AOAM532sCMw/ULAi9iIJoCLlov6jUyrx4tDPVB/edihGD3fvheFn9MsS pwnUImDWlqqor6rpGjQ+t1RBzg== X-Google-Smtp-Source: ABdhPJzQL7u7xXceY/a/6NO6FFVvbZrOOoq5J4p9hCKPlG2yrzzaPNHWsT+RvFgxM6YyCQy3Zb0SVw== X-Received: by 2002:a1c:43c5:: with SMTP id q188mr228308wma.94.1615908793379; Tue, 16 Mar 2021 08:33:13 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id h22sm3985078wmb.36.2021.03.16.08.33.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Mar 2021 08:33:12 -0700 (PDT) From: Daniel Vetter To: DRI Development , LKML Cc: kvm@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-media@vger.kernel.org, Daniel Vetter , Daniel Vetter , Christoph Hellwig , Jason Gunthorpe , Kees Cook , Dan Williams , Andrew Morton , John Hubbard , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Jan Kara Subject: [PATCH 1/3] mm: Add unsafe_follow_pfn Date: Tue, 16 Mar 2021 16:33:01 +0100 Message-Id: <20210316153303.3216674-2-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210316153303.3216674-1-daniel.vetter@ffwll.ch> References: <20210316153303.3216674-1-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org 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. Also mark up follow_pfn as EXPORT_SYMBOL_GPL. The only safe way to use that by drivers/modules is together with an mmu_notifier, and that's all _GPL stuff. Signed-off-by: Daniel Vetter Cc: Christoph Hellwig 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 Signed-off-by: Daniel Vetter Reviewed-by: Jason Gunthorpe --- v5: Suggestions from Christoph - reindent for less weirdness - use IS_ENABLED instead of #ifdef - same checks for nommu, for consistency - EXPORT_SYMBOL_GPL for follow_pfn. - kerneldoc was already updated in previous versions to explain when follow_pfn can be used safely --- include/linux/mm.h | 2 ++ mm/memory.c | 34 ++++++++++++++++++++++++++++++++-- mm/nommu.c | 27 ++++++++++++++++++++++++++- security/Kconfig | 13 +++++++++++++ 4 files changed, 73 insertions(+), 3 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 64a71bf20536..caec8b25d66f 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1695,6 +1695,8 @@ int follow_pte(struct mm_struct *mm, unsigned long address, pte_t **ptepp, spinlock_t **ptlp); int follow_pfn(struct vm_area_struct *vma, unsigned long address, unsigned long *pfn); +int unsafe_follow_pfn(struct vm_area_struct *vma, unsigned long address, + unsigned long *pfn); int follow_phys(struct vm_area_struct *vma, unsigned long address, unsigned int flags, unsigned long *prot, resource_size_t *phys); int generic_access_phys(struct vm_area_struct *vma, unsigned long addr, diff --git a/mm/memory.c b/mm/memory.c index 5efa07fb6cdc..e8a145505b69 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4741,7 +4741,12 @@ EXPORT_SYMBOL_GPL(follow_pte); * @address: user virtual address * @pfn: location to store found PFN * - * Only IO mappings and raw PFN mappings are allowed. + * Only IO mappings and raw PFN mappings are allowed. Note that callers must + * ensure coherency with pte updates by using a &mmu_notifier to follow updates. + * If this is not feasible, or the access to the @pfn is only very short term, + * use follow_pte_pmd() instead and hold the pagetable lock for the duration of + * the access instead. Any caller not following these requirements must use + * unsafe_follow_pfn() instead. * * This function does not allow the caller to read the permissions * of the PTE. Do not use it. @@ -4765,7 +4770,32 @@ int follow_pfn(struct vm_area_struct *vma, unsigned long address, pte_unmap_unlock(ptep, ptl); return 0; } -EXPORT_SYMBOL(follow_pfn); +EXPORT_SYMBOL_GPL(follow_pfn); + +/** + * unsafe_follow_pfn - look up PFN at a user virtual address + * @vma: memory mapping + * @address: user virtual address + * @pfn: location to store found PFN + * + * Only IO mappings and raw PFN mappings are allowed. + * + * Returns zero and the pfn at @pfn on success, -ve otherwise. + */ +int unsafe_follow_pfn(struct vm_area_struct *vma, unsigned long address, + unsigned long *pfn) +{ + if (IS_ENABLED(CONFIG_STRICT_FOLLOW_PFN)) { + pr_info("unsafe follow_pfn usage rejected, see CONFIG_STRICT_FOLLOW_PFN\n"); + return -EINVAL; + } + + WARN_ONCE(1, "unsafe follow_pfn usage\n"); + add_taint(TAINT_USER, LOCKDEP_STILL_OK); + + return follow_pfn(vma, address, pfn); +} +EXPORT_SYMBOL(unsafe_follow_pfn); #ifdef CONFIG_HAVE_IOREMAP_PROT int follow_phys(struct vm_area_struct *vma, diff --git a/mm/nommu.c b/mm/nommu.c index 5c9ab799c0e6..1dc983f50e2c 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -130,7 +130,32 @@ int follow_pfn(struct vm_area_struct *vma, unsigned long address, *pfn = address >> PAGE_SHIFT; return 0; } -EXPORT_SYMBOL(follow_pfn); +EXPORT_SYMBOL_GPL(follow_pfn); + +/** + * unsafe_follow_pfn - look up PFN at a user virtual address + * @vma: memory mapping + * @address: user virtual address + * @pfn: location to store found PFN + * + * Only IO mappings and raw PFN mappings are allowed. + * + * Returns zero and the pfn at @pfn on success, -ve otherwise. + */ +int unsafe_follow_pfn(struct vm_area_struct *vma, unsigned long address, + unsigned long *pfn) +{ + if (IS_ENABLED(CONFIG_STRICT_FOLLOW_PFN)) { + pr_info("unsafe follow_pfn usage rejected, see CONFIG_STRICT_FOLLOW_PFN\n"); + return -EINVAL; + } + + WARN_ONCE(1, "unsafe follow_pfn usage\n"); + add_taint(TAINT_USER, LOCKDEP_STILL_OK); + + return follow_pfn(vma, address, pfn); +} +EXPORT_SYMBOL(unsafe_follow_pfn); LIST_HEAD(vmap_area_list); diff --git a/security/Kconfig b/security/Kconfig index 7561f6f99f1d..48945402e103 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -230,6 +230,19 @@ config STATIC_USERMODEHELPER_PATH If you wish for all usermode helper programs to be disabled, specify an empty string here (i.e. ""). +config STRICT_FOLLOW_PFN + bool "Disable unsafe use of follow_pfn" + depends on MMU + help + Some functionality in the kernel follows userspace mappings to iomem + ranges in an unsafe matter. Examples include v4l userptr for zero-copy + buffers sharing. + + If this option is switched on, such access is rejected. Only enable + this option when you must run userspace which requires this. + + If in doubt, say Y. + source "security/selinux/Kconfig" source "security/smack/Kconfig" source "security/tomoyo/Kconfig" From patchwork Tue Mar 16 15:33:02 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 12142519 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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 B4678C433E6 for ; Tue, 16 Mar 2021 15:34:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8602E60200 for ; Tue, 16 Mar 2021 15:34:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238101AbhCPPdv (ORCPT ); Tue, 16 Mar 2021 11:33:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36880 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237228AbhCPPdQ (ORCPT ); Tue, 16 Mar 2021 11:33:16 -0400 Received: from mail-wm1-x333.google.com (mail-wm1-x333.google.com [IPv6:2a00:1450:4864:20::333]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BCAD9C061756 for ; Tue, 16 Mar 2021 08:33:15 -0700 (PDT) Received: by mail-wm1-x333.google.com with SMTP id f22-20020a7bc8d60000b029010c024a1407so1709331wml.2 for ; Tue, 16 Mar 2021 08:33:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=tAmsDn5BdzFpIsfSDcu5mIHmvLYc/wJQn0BecfxLgl0=; b=ME4sGumFgKYUCqwSU9ZCBXBRBDOTgxTwFtahv+NVAVJHr+fD8AUrznH+V7FRtA8gOj B+CFMjnx7WbKUqyhiMCsTbXLvmFggAn1SQaPCFAka4KTPpVgwdX/WNFBVl3rpTLAziJj STDnUtNyyxJvOuElf8oAxewCR7SdYgUMXzeAE= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=tAmsDn5BdzFpIsfSDcu5mIHmvLYc/wJQn0BecfxLgl0=; b=HMTwnvhInJl7SPTp/pMQhp86OVTDY6I+EsxyzVVWFEmunjK4iNb74mBvmlHO2YW4pu fF5b4VBEmbnD7m0OCYL+8sidiBPZ7MhfUz6T2h9RG+WQIZQz3wM/aK9+IuLugzeNfL3N Q5522s5TcoS8gUBc54fzqxMNyGjNl8SPLw2+EElQcY1sv8Kp0rKFpUtRGSL1X5tuLlzM pRX7ShAbk92PBhplgruG1bxIRy1JsCa/vYN94ZX9NUhtYoDFUqynMcJeBiGSVxMRe4dS qNSYG1G4GOAVZ9wUBb8Q6darHaXXFpREMv/dvgm7vUcs51ABTTKXPHy0DwwKiHMPRMXQ SIEw== X-Gm-Message-State: AOAM53168PXH84udlSAmq7csgjbW+cFfCkwCvYamQI6iqwk2uuWhKDPC nwvgrTzJ3cG0S7x1eJxoeAWLdw== X-Google-Smtp-Source: ABdhPJxdFzaSGBW2sfC8QBc+tMQBXV96M89NWylJdwfCrwV7xrFzVSLG4KZ9deIsLAWFmFnloMhjFw== X-Received: by 2002:a05:600c:4a06:: with SMTP id c6mr209965wmp.35.1615908794565; Tue, 16 Mar 2021 08:33:14 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id h22sm3985078wmb.36.2021.03.16.08.33.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Mar 2021 08:33:14 -0700 (PDT) From: Daniel Vetter To: DRI Development , LKML Cc: kvm@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-media@vger.kernel.org, Daniel Vetter , Tomasz Figa , Hans Verkuil , Daniel Vetter , Jason Gunthorpe , Kees Cook , Dan Williams , Andrew Morton , John Hubbard , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Jan Kara , Pawel Osciak , Marek Szyprowski , Kyungmin Park , Laurent Dufour , Vlastimil Babka , Daniel Jordan , Michel Lespinasse Subject: [PATCH 2/3] media/videobuf1|2: Mark follow_pfn usage as unsafe Date: Tue, 16 Mar 2021 16:33:02 +0100 Message-Id: <20210316153303.3216674-3-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210316153303.3216674-1-daniel.vetter@ffwll.ch> References: <20210316153303.3216674-1-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org The media model assumes that buffers are all preallocated, so that when a media pipeline is running we never miss a deadline because the buffers aren't allocated or available. This means we cannot fix the v4l follow_pfn usage through mmu_notifier, without breaking how this all works. The only real fix is to deprecate userptr support for VM_IO | VM_PFNMAP mappings and tell everyone to cut over to dma-buf memory sharing for zerocopy. userptr for normal memory will keep working as-is, this only affects the zerocopy userptr usage enabled in 50ac952d2263 ("[media] videobuf2-dma-sg: Support io userptr operations on io memory"). Acked-by: Tomasz Figa Acked-by: Hans Verkuil 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: Pawel Osciak Cc: Marek Szyprowski Cc: Kyungmin Park Cc: Tomasz Figa Cc: Laurent Dufour Cc: Vlastimil Babka Cc: Daniel Jordan Cc: Michel Lespinasse Signed-off-by: Daniel Vetter --- v3: - Reference the commit that enabled the zerocopy userptr use case to make it abundandtly clear that this patch only affects that, and not normal memory userptr. The old commit message already explained that normal memory userptr is unaffected, but I guess that was not clear enough. --- drivers/media/common/videobuf2/frame_vector.c | 2 +- drivers/media/v4l2-core/videobuf-dma-contig.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/media/common/videobuf2/frame_vector.c b/drivers/media/common/videobuf2/frame_vector.c index a0e65481a201..1a82ec13ea00 100644 --- a/drivers/media/common/videobuf2/frame_vector.c +++ b/drivers/media/common/videobuf2/frame_vector.c @@ -70,7 +70,7 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames, break; while (ret < nr_frames && start + PAGE_SIZE <= vma->vm_end) { - err = follow_pfn(vma, start, &nums[ret]); + err = unsafe_follow_pfn(vma, start, &nums[ret]); if (err) { if (ret == 0) ret = err; diff --git a/drivers/media/v4l2-core/videobuf-dma-contig.c b/drivers/media/v4l2-core/videobuf-dma-contig.c index 52312ce2ba05..821c4a76ab96 100644 --- a/drivers/media/v4l2-core/videobuf-dma-contig.c +++ b/drivers/media/v4l2-core/videobuf-dma-contig.c @@ -183,7 +183,7 @@ static int videobuf_dma_contig_user_get(struct videobuf_dma_contig_memory *mem, user_address = untagged_baddr; while (pages_done < (mem->size >> PAGE_SHIFT)) { - ret = follow_pfn(vma, user_address, &this_pfn); + ret = unsafe_follow_pfn(vma, user_address, &this_pfn); if (ret) break; From patchwork Tue Mar 16 15:33:03 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 12142521 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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 0B724C43331 for ; Tue, 16 Mar 2021 15:34:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DEFFD650EB for ; Tue, 16 Mar 2021 15:34:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237133AbhCPPdy (ORCPT ); Tue, 16 Mar 2021 11:33:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36892 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238110AbhCPPdR (ORCPT ); Tue, 16 Mar 2021 11:33:17 -0400 Received: from mail-wr1-x436.google.com (mail-wr1-x436.google.com [IPv6:2a00:1450:4864:20::436]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D2AF5C061764 for ; Tue, 16 Mar 2021 08:33:16 -0700 (PDT) Received: by mail-wr1-x436.google.com with SMTP id a18so10675247wrc.13 for ; Tue, 16 Mar 2021 08:33:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=zwe0ekXmy9t5eNr3sFs9jCzA/xhMldV8JLAydoSdCfc=; b=GzG+edIxhOWO3e0C//e9ZTvwmWIMqXUh3qVGupEH1XpIfgojiM9nr7zfSbfVnLpEX1 TppZD/lYq2BFxWK6uExvqhTf4cGvOaXXXtjYXrDDvq/txY4i5BzARGuD/BQ+Nc/vZ9CP U43D7zJSOobDqMzHTu1jMNW+6MtVYMmXPpabc= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=zwe0ekXmy9t5eNr3sFs9jCzA/xhMldV8JLAydoSdCfc=; b=dpX4WcR2ijzZ88eOudwgATu6Z3HMNoC1/MP5LBlhdMOLuk1v3y5APqC/K35Qw96O4s TIfzWigp5qJdm/sa3Kp6Ohl9eqRznBUAyZ0dsK/69yfEdTyS+bDwgUGyPsT4nrlkKv7i o7uA37uPv8WzkbopsMe5uQP6FvzmPLBum8keqXolJzI8GRXR2UFdSNp6ck3GtHx8W2ox NuXZepFhSB+OwCmzL6X7CAGtbV1DvsxLBpfnwmywHMj3ps8dQcTAUam4nqhQJtbLUUzy iyHQriX2usLydgNDfp0CUj80FZsbeNJ3ILO/BL8DiJdzXzDJDdgi9iqbjJv4jSakVOEa U/4w== X-Gm-Message-State: AOAM531blbTBtDqtZK042Zb2II1vV+RxEPLVdg6q8/EPPJ3SnrkTxBax RVevyOqbj+jqeZWn2CzXkHyzaw== X-Google-Smtp-Source: ABdhPJxsQT1ztD0lh1/0ccaL0ZTcHbZx32nTGgPOptwOia/Vap2jPDUXToCOLm5fL6HRJJsLfse8jA== X-Received: by 2002:adf:ec0b:: with SMTP id x11mr5396504wrn.175.1615908795642; Tue, 16 Mar 2021 08:33:15 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id h22sm3985078wmb.36.2021.03.16.08.33.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Mar 2021 08:33:15 -0700 (PDT) From: Daniel Vetter To: DRI Development , LKML Cc: kvm@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-media@vger.kernel.org, Daniel Vetter , 3pvd@google.com, Jann Horn , Paolo Bonzini , Jason Gunthorpe , Cornelia Huck , Peter Xu , Alex Williamson , Daniel Vetter Subject: [PATCH 3/3] mm: unexport follow_pfn Date: Tue, 16 Mar 2021 16:33:03 +0100 Message-Id: <20210316153303.3216674-4-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210316153303.3216674-1-daniel.vetter@ffwll.ch> References: <20210316153303.3216674-1-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Both kvm (in bd2fae8da794 ("KVM: do not assume PTE is writable after follow_pfn")) and vfio (in 07956b6269d3 ("vfio/type1: Use follow_pte()")) have lost their callsites of follow_pfn(). All the other ones have been switched over to unsafe_follow_pfn because they cannot be fixed without breaking userspace api. Argueably the vfio code is still racy, but that's kinda a bigger picture. But since it does leak the pte beyond where it drops the pt lock, without anything else like an mmu notifier guaranteeing coherence, the problem is at least clearly visible in the vfio code. So good enough with me. I've decided to keep the explanation that after dropping the pt lock you must have an mmu notifier if you keep using the pte somehow by adjusting it and moving it into the kerneldoc for the new follow_pte() function. Cc: 3pvd@google.com Cc: Jann Horn Cc: Paolo Bonzini Cc: Jason Gunthorpe Cc: Cornelia Huck Cc: Peter Xu Cc: Alex Williamson 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 Signed-off-by: Daniel Vetter Reviewed-by: Jason Gunthorpe --- include/linux/mm.h | 2 -- mm/memory.c | 26 +++++--------------------- mm/nommu.c | 13 +------------ 3 files changed, 6 insertions(+), 35 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index caec8b25d66f..304588e2f829 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1693,8 +1693,6 @@ int follow_invalidate_pte(struct mm_struct *mm, unsigned long address, pmd_t **pmdpp, spinlock_t **ptlp); int follow_pte(struct mm_struct *mm, unsigned long address, pte_t **ptepp, spinlock_t **ptlp); -int follow_pfn(struct vm_area_struct *vma, unsigned long address, - unsigned long *pfn); int unsafe_follow_pfn(struct vm_area_struct *vma, unsigned long address, unsigned long *pfn); int follow_phys(struct vm_area_struct *vma, unsigned long address, diff --git a/mm/memory.c b/mm/memory.c index e8a145505b69..317e653c8aeb 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4724,7 +4724,10 @@ int follow_invalidate_pte(struct mm_struct *mm, unsigned long address, * should be taken for read. * * KVM uses this function. While it is arguably less bad than ``follow_pfn``, - * it is not a good general-purpose API. + * it is not a good general-purpose API: If callers use the pte after they've + * unlocked @ptlp they must ensure coherency with pte updates by using a + * &mmu_notifier to follow updates. Any caller not following these requirements + * must use unsafe_follow_pfn() instead. * * Return: zero on success, -ve otherwise. */ @@ -4735,25 +4738,7 @@ int follow_pte(struct mm_struct *mm, unsigned long address, } EXPORT_SYMBOL_GPL(follow_pte); -/** - * follow_pfn - look up PFN at a user virtual address - * @vma: memory mapping - * @address: user virtual address - * @pfn: location to store found PFN - * - * Only IO mappings and raw PFN mappings are allowed. Note that callers must - * ensure coherency with pte updates by using a &mmu_notifier to follow updates. - * If this is not feasible, or the access to the @pfn is only very short term, - * use follow_pte_pmd() instead and hold the pagetable lock for the duration of - * the access instead. Any caller not following these requirements must use - * unsafe_follow_pfn() instead. - * - * This function does not allow the caller to read the permissions - * of the PTE. Do not use it. - * - * Return: zero and the pfn at @pfn on success, -ve otherwise. - */ -int follow_pfn(struct vm_area_struct *vma, unsigned long address, +static int follow_pfn(struct vm_area_struct *vma, unsigned long address, unsigned long *pfn) { int ret = -EINVAL; @@ -4770,7 +4755,6 @@ int follow_pfn(struct vm_area_struct *vma, unsigned long address, pte_unmap_unlock(ptep, ptl); return 0; } -EXPORT_SYMBOL_GPL(follow_pfn); /** * unsafe_follow_pfn - look up PFN at a user virtual address diff --git a/mm/nommu.c b/mm/nommu.c index 1dc983f50e2c..cee29d0791b3 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -111,17 +111,7 @@ unsigned int kobjsize(const void *objp) return page_size(page); } -/** - * follow_pfn - look up PFN at a user virtual address - * @vma: memory mapping - * @address: user virtual address - * @pfn: location to store found PFN - * - * Only IO mappings and raw PFN mappings are allowed. - * - * Returns zero and the pfn at @pfn on success, -ve otherwise. - */ -int follow_pfn(struct vm_area_struct *vma, unsigned long address, +static int follow_pfn(struct vm_area_struct *vma, unsigned long address, unsigned long *pfn) { if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) @@ -130,7 +120,6 @@ int follow_pfn(struct vm_area_struct *vma, unsigned long address, *pfn = address >> PAGE_SHIFT; return 0; } -EXPORT_SYMBOL_GPL(follow_pfn); /** * unsafe_follow_pfn - look up PFN at a user virtual address