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=-19.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 2E018C433DB for ; Wed, 10 Feb 2021 02:37:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0570364E32 for ; Wed, 10 Feb 2021 02:37:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235039AbhBJChe (ORCPT ); Tue, 9 Feb 2021 21:37:34 -0500 Received: from mail.kernel.org ([198.145.29.99]:33470 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235227AbhBJCea (ORCPT ); Tue, 9 Feb 2021 21:34:30 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 5BDB264E28; Wed, 10 Feb 2021 02:33:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1612924429; bh=3PofB5kHE1Droc1l/x/NzzxCy7Pe3oO6umr2zP7azEc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uVqAKWrTDchR3ibGOojrsPOepUBo1IWclpu6zNhM/ncnlVE2/5GEbBtRoc2Og9s0o eU7IEX/qcoXjlagmQWfpuP2K0fgUX4trY2WceU5c8usJnzIUepONb8T5/WwLK09c7D uosXUrRrP5rZ+PZ/11eelL4Ix4sekq8STINju44whmaRiYR48hVojq78X5EGW7J3/Q e0WzGc3Tle2+EAkfi4onhioOicwGEhgByPL70ChRPDjt6b8CNkJVNCg8VFNhwoDCiS JJGv4fZz7TFuYjEFYLY2je0ReUDqtUfkVSTw07oxiddLjSJQMmJsGtYGxjbBU2nRLY iAzpaxO/H5BVg== From: Andy Lutomirski To: x86@kernel.org Cc: LKML , Dave Hansen , Alexei Starovoitov , Daniel Borkmann , Yonghong Song , Masami Hiramatsu , Andy Lutomirski , stable@vger.kernel.org, Peter Zijlstra , Christoph Hellwig Subject: [PATCH v2 01/14] x86/fault: Fix AMD erratum #91 errata fixup for user code Date: Tue, 9 Feb 2021 18:33:33 -0800 Message-Id: X-Mailer: git-send-email 2.29.2 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The recent rework of probe_kernel_address() and its conversion to get_kernel_nofault() inadvertently broke is_prefetch(). Before this change, probe_kernel_address() was used as a sloppy "read user or kernel memory" helper, but it doesn't do that any more. The new get_kernel_nofault() reads *kernel* memory only, which completely broke is_prefetch() for user access. Adjust the code to the the correct accessor based on access mode. The manual address bounds check is no longer necessary, since the accessor helpers (get_user() / get_kernel_nofault()) do the right thing all by themselves. As a bonus, by using the correct accessor, we don't need the open-coded address bounds check. Fixes: eab0c6089b68 ("maccess: unify the probe kernel arch hooks") Cc: stable@vger.kernel.org Cc: Dave Hansen Cc: Peter Zijlstra Cc: Christoph Hellwig Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: Masami Hiramatsu Signed-off-by: Andy Lutomirski --- arch/x86/mm/fault.c | 27 +++++++++++++++++---------- 1 file changed, 17 insertions(+), 10 deletions(-) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index f1f1b5a0956a..441c3e9b8971 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -54,7 +54,7 @@ kmmio_fault(struct pt_regs *regs, unsigned long addr) * 32-bit mode: * * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch. - * Check that here and ignore it. + * Check that here and ignore it. This is AMD erratum #91. * * 64-bit mode: * @@ -83,11 +83,7 @@ check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr, #ifdef CONFIG_X86_64 case 0x40: /* - * In AMD64 long mode 0x40..0x4F are valid REX prefixes - * Need to figure out under what instruction mode the - * instruction was issued. Could check the LDT for lm, - * but for now it's good enough to assume that long - * mode only uses well known segments or kernel. + * In 64-bit mode 0x40..0x4F are valid REX prefixes */ return (!user_mode(regs) || user_64bit_mode(regs)); #endif @@ -127,20 +123,31 @@ is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr) instr = (void *)convert_ip_to_linear(current, regs); max_instr = instr + 15; - if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX) - return 0; + /* + * This code has historically always bailed out if IP points to a + * not-present page (e.g. due to a race). No one has ever + * complained about this. + */ + pagefault_disable(); while (instr < max_instr) { unsigned char opcode; - if (get_kernel_nofault(opcode, instr)) - break; + if (user_mode(regs)) { + if (get_user(opcode, instr)) + break; + } else { + if (get_kernel_nofault(opcode, instr)) + break; + } instr++; if (!check_prefetch_opcode(regs, instr, opcode, &prefetch)) break; } + + pagefault_enable(); return prefetch; } -- 2.29.2