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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 92E44C06510 for ; Wed, 3 Jul 2019 02:18:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 64DF42187F for ; Wed, 3 Jul 2019 02:18:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1562120320; bh=6hQsemkxImaDJCUqYWKffBbCMlJUrsMfuYi1mxHeXl4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=SoREhb0+ws7IyRCzVWLTBORW0AqLrDZctPVPqL0uo0HUyH6ZxG7tFR+EuvpYkCLAi jKKMAHATLOkUX/iC2ybX5isYSthN7F4+GhBzf0i9SaBunPDaKVjUnFpXPkkGtvOAM7 Gvy594HB4Qj2sZi5AgMuVakSMfCvLxk2b4F5KIdU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728293AbfGCCSi (ORCPT ); Tue, 2 Jul 2019 22:18:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:56420 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727464AbfGCCSa (ORCPT ); Tue, 2 Jul 2019 22:18:30 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8251C21873; Wed, 3 Jul 2019 02:18:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1562120309; bh=6hQsemkxImaDJCUqYWKffBbCMlJUrsMfuYi1mxHeXl4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tn/qju4QJdXXsLu1kSF63L9bDgzzLkg7+hU5953GEVOVqemSe0mdSR2H2ifhAZKfQ wG54wd5ZDN/K8iB7oLVTJoz2cDq4nWDIHwbFpg/TRMhshbX+T1N3M661LGY+ANn3nP RguqY3rnDvXuwn36JAY2TRT1UulUBiFHDfCHK+IM= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Kirill A. Shutemov" , "Kirill A . Shutemov" , Thomas Gleixner , Borislav Petkov , "H. Peter Anvin" , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Sasha Levin Subject: [PATCH AUTOSEL 4.14 11/13] x86/boot/64: Fix crash if kernel image crosses page table boundary Date: Tue, 2 Jul 2019 22:18:12 -0400 Message-Id: <20190703021814.18385-11-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190703021814.18385-1-sashal@kernel.org> References: <20190703021814.18385-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Kirill A. Shutemov" [ Upstream commit 81c7ed296dcd02bc0b4488246d040e03e633737a ] A kernel which boots in 5-level paging mode crashes in a small percentage of cases if KASLR is enabled. This issue was tracked down to the case when the kernel image unpacks in a way that it crosses an 1G boundary. The crash is caused by an overrun of the PMD page table in __startup_64() and corruption of P4D page table allocated next to it. This particular issue is not visible with 4-level paging as P4D page tables are not used. But the P4D and the PUD calculation have similar problems. The PMD index calculation is wrong due to operator precedence, which fails to confine the PMDs in the PMD array on wrap around. The P4D calculation for 5-level paging and the PUD calculation calculate the first index correctly, but then blindly increment it which causes the same issue when a kernel image is located across a 512G and for 5-level paging across a 46T boundary. This wrap around mishandling was introduced when these parts moved from assembly to C. Restore it to the correct behaviour. Fixes: c88d71508e36 ("x86/boot/64: Rewrite startup_64() in C") Signed-off-by: Kirill A. Shutemov Signed-off-by: Thomas Gleixner Cc: Borislav Petkov Cc: "H. Peter Anvin" Cc: Dave Hansen Cc: Andy Lutomirski Cc: Peter Zijlstra Link: https://lkml.kernel.org/r/20190620112345.28833-1-kirill.shutemov@linux.intel.com Signed-off-by: Sasha Levin --- arch/x86/kernel/head64.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index 45b5c6c4a55e..7c67d8939f3e 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -117,26 +117,27 @@ unsigned long __head __startup_64(unsigned long physaddr, pgd[i + 0] = (pgdval_t)p4d + pgtable_flags; pgd[i + 1] = (pgdval_t)p4d + pgtable_flags; - i = (physaddr >> P4D_SHIFT) % PTRS_PER_P4D; - p4d[i + 0] = (pgdval_t)pud + pgtable_flags; - p4d[i + 1] = (pgdval_t)pud + pgtable_flags; + i = physaddr >> P4D_SHIFT; + p4d[(i + 0) % PTRS_PER_P4D] = (pgdval_t)pud + pgtable_flags; + p4d[(i + 1) % PTRS_PER_P4D] = (pgdval_t)pud + pgtable_flags; } else { i = (physaddr >> PGDIR_SHIFT) % PTRS_PER_PGD; pgd[i + 0] = (pgdval_t)pud + pgtable_flags; pgd[i + 1] = (pgdval_t)pud + pgtable_flags; } - i = (physaddr >> PUD_SHIFT) % PTRS_PER_PUD; - pud[i + 0] = (pudval_t)pmd + pgtable_flags; - pud[i + 1] = (pudval_t)pmd + pgtable_flags; + i = physaddr >> PUD_SHIFT; + pud[(i + 0) % PTRS_PER_PUD] = (pudval_t)pmd + pgtable_flags; + pud[(i + 1) % PTRS_PER_PUD] = (pudval_t)pmd + pgtable_flags; pmd_entry = __PAGE_KERNEL_LARGE_EXEC & ~_PAGE_GLOBAL; pmd_entry += sme_get_me_mask(); pmd_entry += physaddr; for (i = 0; i < DIV_ROUND_UP(_end - _text, PMD_SIZE); i++) { - int idx = i + (physaddr >> PMD_SHIFT) % PTRS_PER_PMD; - pmd[idx] = pmd_entry + i * PMD_SIZE; + int idx = i + (physaddr >> PMD_SHIFT); + + pmd[idx % PTRS_PER_PMD] = pmd_entry + i * PMD_SIZE; } /* -- 2.20.1