From patchwork Mon Mar 1 16:14:01 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: 389137 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=-18.8 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 27CDBC433E6 for ; Mon, 1 Mar 2021 20:29:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C00C564DCF for ; Mon, 1 Mar 2021 20:29:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241215AbhCAU1Y (ORCPT ); Mon, 1 Mar 2021 15:27:24 -0500 Received: from mail.kernel.org ([198.145.29.99]:44018 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242929AbhCAUVI (ORCPT ); Mon, 1 Mar 2021 15:21:08 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id BED3D64F4D; Mon, 1 Mar 2021 18:04:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1614621866; bh=L38SFZeTvskcp+RdHGxsVI9yUjtX5EJdHPnncN75XY4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MgQS8PXBF7gU7Kz1vQtUHeF+HmTDJ+s20lnEmJZbXkFZ369FJC65mwMRsn4PU4TKt MxWDF9IF7zTwtzd/uZmRj9M1Z7vo4PGw9IhoXNUzEpr1jUI/Q8pq4ghcPdDTsN/Cw8 WzyG/By24Xd2hL11BGRM9fENJ8sXHwNYwuiJVmUA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Andy Lutomirski , Borislav Petkov , Christoph Hellwig Subject: [PATCH 5.11 673/775] x86/fault: Fix AMD erratum #91 errata fixup for user code Date: Mon, 1 Mar 2021 17:14:01 +0100 Message-Id: <20210301161234.639893701@linuxfoundation.org> X-Mailer: git-send-email 2.30.1 In-Reply-To: <20210301161201.679371205@linuxfoundation.org> References: <20210301161201.679371205@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Andy Lutomirski commit 35f1c89b0cce247bf0213df243ed902989b1dcda upstream. 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 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, the open-coded address bounds check is not needed anymore. [ bp: Massage commit message. ] Fixes: eab0c6089b68 ("maccess: unify the probe kernel arch hooks") Signed-off-by: Andy Lutomirski Signed-off-by: Borislav Petkov Reviewed-by: Christoph Hellwig Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/b91f7f92f3367d2d3a88eec3b09c6aab1b2dc8ef.1612924255.git.luto@kernel.org Signed-off-by: Greg Kroah-Hartman --- arch/x86/mm/fault.c | 27 +++++++++++++++++---------- 1 file changed, 17 insertions(+), 10 deletions(-) --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -54,7 +54,7 @@ kmmio_fault(struct pt_regs *regs, unsign * 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 *re #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, unsign 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; }