From patchwork Fri Mar 4 09:35:12 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jarkko Sakkinen X-Patchwork-Id: 12768836 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 88689C4321E for ; Fri, 4 Mar 2022 09:38:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237514AbiCDJip (ORCPT ); Fri, 4 Mar 2022 04:38:45 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53972 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239440AbiCDJiK (ORCPT ); Fri, 4 Mar 2022 04:38:10 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 245A91A7DB4; Fri, 4 Mar 2022 01:37:05 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id AD3D161631; Fri, 4 Mar 2022 09:37:04 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 834E1C340E9; Fri, 4 Mar 2022 09:37:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1646386623; bh=XaeaiWxlktYedaApb7MGtb/X/9dEnZ9X6kqkinK/b0U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HmrMGkMMpwoInVQeT4IEeiAsGsS0L0Sv9FciUvaMHj6505mx8UlDLTc2bHYTh00Wb 3nSNjNXa4z2yEN0Alc5ntYJ5k7wNc5gvjlTua4V6Mn5rB2L55SUBksx9HpTcmlI1NY w5hncpQ1HZlZse3Mryx5A9wA3F+sYlJfFVfVL+DiGw1zRtkdVjpfXX0U3C3shjySTj zpgcoGAlnC+0hzzKtY6f4awbZSvqJCIWWCTAvtPuJrfCymKhqUfbrPeuy70TqedEq8 mclRCeuSx8RYcmv2eWqlO3M746VCv8ihyViNOo2wbG9b/oh+EPkyl6GNJENHoB1iUn eXQUlHNI7zWFw== From: Jarkko Sakkinen To: linux-sgx@vger.kernel.org Cc: Nathaniel McCallum , Reinette Chatre , Jarkko Sakkinen , Dave Hansen , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)), "H. Peter Anvin" , linux-kernel@vger.kernel.org (open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)) Subject: [RFC PATCH v2.1 18/30] x86/sgx: Tighten accessible memory range after enclave initialization Date: Fri, 4 Mar 2022 11:35:12 +0200 Message-Id: <20220304093524.397485-18-jarkko@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220304093524.397485-1-jarkko@kernel.org> References: <20220304093524.397485-1-jarkko@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org From: Reinette Chatre Before an enclave is initialized the enclave's memory range is unknown. The enclave's memory range is learned at the time it is created via the SGX_IOC_ENCLAVE_CREATE ioctl() where the provided memory range is obtained from an earlier mmap() of /dev/sgx_enclave. After an enclave is initialized its memory can be mapped into user space (mmap()) from where it can be entered at its defined entry points. With the enclave's memory range known after it is initialized there is no reason why it should be possible to map memory outside this range. Lock down access to the initialized enclave's memory range by denying any attempt to map memory outside its memory range. Locking down the memory range also makes adding pages to an initialized enclave more efficient. Pages are added to an initialized enclave by accessing memory that belongs to the enclave's memory range but not yet backed by an enclave page. If it is possible for user space to map memory that does not form part of the enclave then an access to this memory would eventually fail. Failures range from a prompt general protection fault if the access was an ENCLU[EACCEPT] from within the enclave, or a page fault via the vDSO if it was another access from within the enclave, or a SIGBUS (also resulting from a page fault) if the access was from outside the enclave. Disallowing invalid memory to be mapped in the first place avoids preventable failures. Signed-off-by: Reinette Chatre --- arch/x86/kernel/cpu/sgx/encl.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c index 9602b6db831b..f775995a75e2 100644 --- a/arch/x86/kernel/cpu/sgx/encl.c +++ b/arch/x86/kernel/cpu/sgx/encl.c @@ -402,6 +402,11 @@ int sgx_encl_may_map(struct sgx_encl *encl, unsigned long start, XA_STATE(xas, &encl->page_array, PFN_DOWN(start)); + /* Disallow mapping outside enclave's address range. */ + if (test_bit(SGX_ENCL_INITIALIZED, &encl->flags) && + (start < encl->base || end > encl->base + encl->size)) + return -EACCES; + /* * Disallow READ_IMPLIES_EXEC tasks as their VMA permissions might * conflict with the enclave page permissions.