From patchwork Mon Oct 26 10:58:11 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 286080 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=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, 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 EA61CC63697 for ; Mon, 26 Oct 2020 10:59:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B3EBB2231B for ; Mon, 26 Oct 2020 10:59:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ffwll.ch header.i=@ffwll.ch header.b="LeOH7Nu7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1772945AbgJZK7p (ORCPT ); Mon, 26 Oct 2020 06:59:45 -0400 Received: from mail-wm1-f68.google.com ([209.85.128.68]:54852 "EHLO mail-wm1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1772585AbgJZK6j (ORCPT ); Mon, 26 Oct 2020 06:58:39 -0400 Received: by mail-wm1-f68.google.com with SMTP id w23so10050338wmi.4 for ; Mon, 26 Oct 2020 03:58:37 -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=Jw8O4zHShCAt4bi/mdSwE8pqaQ/Ci7nnAmM3jj6tKas=; b=LeOH7Nu7nYyzs6z+/KfV+foE7RZUakypEXEfU/vXenF6NA90yn3buwHE0Uu6W+NU5m Hi0AM14GFSueByuFTd94ZbnLe28erHjzsMvKFy0Os9VwT8Ga/ABZUV2quSB96oh4ck2n HGBn3CIltcz0TR3fcsi6KP6WJJBm9e95NWE9o= 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=Jw8O4zHShCAt4bi/mdSwE8pqaQ/Ci7nnAmM3jj6tKas=; b=hoSkMldBjWl+8ZKg2L963do8XBkT+wnxRTgtY+LtK+o6tMMbWrq122OLS8Yu6V62bl rOVp4JzRT3VrWTh7lT+Mjem4O9dtJ2ZWFMVxt7ZLy/HEXR28bgj2h2Vv/4f2JFdlmxew hsbMBpjihtXqnHK8UQmVUAMalqXavrbVvkvW9aGS3okJ67ppvvpJC3/ECTENXjnfRlS4 YDrWi5r8WhlV/RNx9V9foKDBbeBiHQjXe60XKRZ/zNFxaJTBsem8gtuInQUxC1PEcaBL TO5Y/Yo0DP81Yt0TWEOm0OPP/7sawJnRs449UGR9oshvk52D/vA2V12VbAf6XN8nA87E 1hKg== X-Gm-Message-State: AOAM5309jKkcld/arf660X527ZIqzIGRoWNRddxt3XtbqVAa+cfdhBUd USvcYWYnJJCXk5uV0d4f/QHIeg== X-Google-Smtp-Source: ABdhPJwBkNEqxu0ChR0X2FBJPl4+XpnvlFPrjyvJkxjB1QLwg8t+SYJeWTboLEwPxYM+uDVWyRzgsA== X-Received: by 2002:a1c:6643:: with SMTP id a64mr15848860wmc.142.1603709916809; Mon, 26 Oct 2020 03:58:36 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id w83sm21165156wmg.48.2020.10.26.03.58.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Oct 2020 03:58:36 -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, linux-s390@vger.kernel.org, Daniel Vetter , Daniel Vetter , Jason Gunthorpe , Kees Cook , Dan Williams , Andrew Morton , John Hubbard , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Jan Kara Subject: [PATCH v4 08/15] mm: Add unsafe_follow_pfn Date: Mon, 26 Oct 2020 11:58:11 +0100 Message-Id: <20201026105818.2585306-9-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20201026105818.2585306-1-daniel.vetter@ffwll.ch> References: <20201026105818.2585306-1-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-media@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. 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 Signed-off-by: Daniel Vetter --- include/linux/mm.h | 2 ++ mm/memory.c | 32 +++++++++++++++++++++++++++++++- mm/nommu.c | 17 +++++++++++++++++ security/Kconfig | 13 +++++++++++++ 4 files changed, 63 insertions(+), 1 deletion(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 2a16631c1fda..ec8c90928fc9 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1653,6 +1653,8 @@ int follow_pte_pmd(struct mm_struct *mm, unsigned long address, pte_t **ptepp, pmd_t **pmdpp, 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 1b46eae3b703..9a2ec07ff20b 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4788,7 +4788,12 @@ EXPORT_SYMBOL(follow_pte_pmd); * @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. * * Return: zero and the pfn at @pfn on success, -ve otherwise. */ @@ -4811,6 +4816,31 @@ int follow_pfn(struct vm_area_struct *vma, unsigned long address, } EXPORT_SYMBOL(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) +{ +#ifdef CONFIG_STRICT_FOLLOW_PFN + pr_info("unsafe follow_pfn usage rejected, see CONFIG_STRICT_FOLLOW_PFN\n"); + return -EINVAL; +#else + WARN_ONCE(1, "unsafe follow_pfn usage\n"); + add_taint(TAINT_USER, LOCKDEP_STILL_OK); + + return follow_pfn(vma, address, pfn); +#endif +} +EXPORT_SYMBOL(unsafe_follow_pfn); + #ifdef CONFIG_HAVE_IOREMAP_PROT int follow_phys(struct vm_area_struct *vma, unsigned long address, unsigned int flags, diff --git a/mm/nommu.c b/mm/nommu.c index 75a327149af1..3db2910f0d64 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -132,6 +132,23 @@ int follow_pfn(struct vm_area_struct *vma, unsigned long address, } EXPORT_SYMBOL(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) +{ + return follow_pfn(vma, address, pfn); +} +EXPORT_SYMBOL(unsafe_follow_pfn); + LIST_HEAD(vmap_area_list); void vfree(const void *addr) 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"