From patchwork Mon Mar 15 13:52:03 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 401562 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=-19.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham 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 E1853C2D0C3 for ; Mon, 15 Mar 2021 13:58:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BEBAE64F29 for ; Mon, 15 Mar 2021 13:58:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232215AbhCON54 (ORCPT ); Mon, 15 Mar 2021 09:57:56 -0400 Received: from mail.kernel.org ([198.145.29.99]:34948 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231965AbhCON5Y (ORCPT ); Mon, 15 Mar 2021 09:57:24 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id D864564F2D; Mon, 15 Mar 2021 13:57:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1615816644; bh=KUgnUfIhMV6ghQ263E7VfkbB5r4OQ8SSZIpzaryCweQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=V/VBLTZwuW1PfHDYW6mSJo9qIztITKt5A2cwR+8G7dzd8pcuFjBFA9a/n6FtxxG/I rSPiMWeur5CWZ1eUXZu5BBee7KiP1ppymQiIq3vQbIHgYFj/jSWYUU28yMqwUpqzAy gjfMR5RjCVP0vx63NgXDWdMbBFiWbAnuNkB1vxoY= From: gregkh@linuxfoundation.org To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Christoph Plattner , Christophe Leroy , Michael Ellerman Subject: [PATCH 5.10 030/290] powerpc/603: Fix protection of user pages mapped with PROT_NONE Date: Mon, 15 Mar 2021 14:52:03 +0100 Message-Id: <20210315135542.940267543@linuxfoundation.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210315135541.921894249@linuxfoundation.org> References: <20210315135541.921894249@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Greg Kroah-Hartman From: Christophe Leroy commit c119565a15a628efdfa51352f9f6c5186e506a1c upstream. On book3s/32, page protection is defined by the PP bits in the PTE which provide the following protection depending on the access keys defined in the matching segment register: - PP 00 means RW with key 0 and N/A with key 1. - PP 01 means RW with key 0 and RO with key 1. - PP 10 means RW with both key 0 and key 1. - PP 11 means RO with both key 0 and key 1. Since the implementation of kernel userspace access protection, PP bits have been set as follows: - PP00 for pages without _PAGE_USER - PP01 for pages with _PAGE_USER and _PAGE_RW - PP11 for pages with _PAGE_USER and without _PAGE_RW For kernelspace segments, kernel accesses are performed with key 0 and user accesses are performed with key 1. As PP00 is used for non _PAGE_USER pages, user can't access kernel pages not flagged _PAGE_USER while kernel can. For userspace segments, both kernel and user accesses are performed with key 0, therefore pages not flagged _PAGE_USER are still accessible to the user. This shouldn't be an issue, because userspace is expected to be accessible to the user. But unlike most other architectures, powerpc implements PROT_NONE protection by removing _PAGE_USER flag instead of flagging the page as not valid. This means that pages in userspace that are not flagged _PAGE_USER shall remain inaccessible. To get the expected behaviour, just mimic other architectures in the TLB miss handler by checking _PAGE_USER permission on userspace accesses as if it was the _PAGE_PRESENT bit. Note that this problem only is only for 603 cores. The 604+ have an hash table, and hash_page() function already implement the verification of _PAGE_USER permission on userspace pages. Fixes: f342adca3afc ("powerpc/32s: Prepare Kernel Userspace Access Protection") Cc: stable@vger.kernel.org # v5.2+ Reported-by: Christoph Plattner Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/4a0c6e3bb8f0c162457bf54d9bc6fd8d7b55129f.1612160907.git.christophe.leroy@csgroup.eu Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/kernel/head_book3s_32.S | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) --- a/arch/powerpc/kernel/head_book3s_32.S +++ b/arch/powerpc/kernel/head_book3s_32.S @@ -461,10 +461,11 @@ InstructionTLBMiss: cmplw 0,r1,r3 #endif mfspr r2, SPRN_SPRG_PGDIR - li r1,_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_EXEC + li r1,_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_EXEC | _PAGE_USER #if defined(CONFIG_MODULES) || defined(CONFIG_DEBUG_PAGEALLOC) bgt- 112f lis r2, (swapper_pg_dir - PAGE_OFFSET)@ha /* if kernel address, use */ + li r1,_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_EXEC addi r2, r2, (swapper_pg_dir - PAGE_OFFSET)@l /* kernel page table */ #endif 112: rlwimi r2,r3,12,20,29 /* insert top 10 bits of address */ @@ -523,9 +524,10 @@ DataLoadTLBMiss: lis r1, TASK_SIZE@h /* check if kernel address */ cmplw 0,r1,r3 mfspr r2, SPRN_SPRG_PGDIR - li r1, _PAGE_PRESENT | _PAGE_ACCESSED + li r1, _PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_USER bgt- 112f lis r2, (swapper_pg_dir - PAGE_OFFSET)@ha /* if kernel address, use */ + li r1, _PAGE_PRESENT | _PAGE_ACCESSED addi r2, r2, (swapper_pg_dir - PAGE_OFFSET)@l /* kernel page table */ 112: rlwimi r2,r3,12,20,29 /* insert top 10 bits of address */ lwz r2,0(r2) /* get pmd entry */ @@ -599,9 +601,10 @@ DataStoreTLBMiss: lis r1, TASK_SIZE@h /* check if kernel address */ cmplw 0,r1,r3 mfspr r2, SPRN_SPRG_PGDIR - li r1, _PAGE_RW | _PAGE_DIRTY | _PAGE_PRESENT | _PAGE_ACCESSED + li r1, _PAGE_RW | _PAGE_DIRTY | _PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_USER bgt- 112f lis r2, (swapper_pg_dir - PAGE_OFFSET)@ha /* if kernel address, use */ + li r1, _PAGE_RW | _PAGE_DIRTY | _PAGE_PRESENT | _PAGE_ACCESSED addi r2, r2, (swapper_pg_dir - PAGE_OFFSET)@l /* kernel page table */ 112: rlwimi r2,r3,12,20,29 /* insert top 10 bits of address */ lwz r2,0(r2) /* get pmd entry */