From patchwork Tue Mar 9 16:08:11 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: thermal-bot for Julien Panis X-Patchwork-Id: 397444 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=-20.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING, SPF_HELO_NONE, SPF_PASS 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 742C1C4332E for ; Tue, 9 Mar 2021 16:09:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 49D53652B9 for ; Tue, 9 Mar 2021 16:09:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231961AbhCIQIn (ORCPT ); Tue, 9 Mar 2021 11:08:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52068 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232054AbhCIQIO (ORCPT ); Tue, 9 Mar 2021 11:08:14 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7B9FDC06174A; Tue, 9 Mar 2021 08:08:14 -0800 (PST) Date: Tue, 09 Mar 2021 16:08:11 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1615306092; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=4oKnzr0uBAmthc+mtFDYGBTY0n/S6HSbqDR1yGD74oY=; b=E32sU3XROmMExlWeHSLp022qB060dzbpQ2hKTHfWC4/ky/IiyauXBi1HyWHAdUo/EtMKXq 1if2zhQ5XqpxI39k4U3wAWQhn/7qhORCCawRvakRADxVb9PhiicdZLMQ2ySosDwcc2mGhC XGm1mx4KJx9yHo/hy6girMA0bEiDIdaEiEStva1A5fxuRZOoPonprlLd8NKwzv4hkLipRB +1Db2tp0LIQ0TGP0EJ9sxbTKmA+b28PuM9Ah752MTL38EGoM2HjKPDheYnBb7Pha1Es54d nGd6x83pz+pSdqGkWxZE/LPPZCuEmjtYyKGH8FE10zTzE9z5dWm3hJuJxCIrVQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1615306092; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=4oKnzr0uBAmthc+mtFDYGBTY0n/S6HSbqDR1yGD74oY=; b=RRKMEb8olJYcGa3jgLm9BHDX50w40whIN+oy0DZW2+jjwrMwst1ZEnwJvYYC873ME5aDkJ UFueFuQkQjzREEDw== From: "tip-bot2 for Joerg Roedel" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/urgent] x86/sev-es: Use __copy_from_user_inatomic() Cc: Joerg Roedel , Borislav Petkov , stable@vger.kernel.org, #@tip-bot2.tec.linutronix.de, v5.10+@tip-bot2.tec.linutronix.de, x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20210303141716.29223-6-joro@8bytes.org> References: <20210303141716.29223-6-joro@8bytes.org> MIME-Version: 1.0 Message-ID: <161530609145.398.11788933296819355210.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The following commit has been merged into the x86/urgent branch of tip: Commit-ID: bffe30dd9f1f3b2608a87ac909a224d6be472485 Gitweb: https://git.kernel.org/tip/bffe30dd9f1f3b2608a87ac909a224d6be472485 Author: Joerg Roedel AuthorDate: Wed, 03 Mar 2021 15:17:16 +01:00 Committer: Borislav Petkov CommitterDate: Tue, 09 Mar 2021 12:37:54 +01:00 x86/sev-es: Use __copy_from_user_inatomic() The #VC handler must run in atomic context and cannot sleep. This is a problem when it tries to fetch instruction bytes from user-space via copy_from_user(). Introduce a insn_fetch_from_user_inatomic() helper which uses __copy_from_user_inatomic() to safely copy the instruction bytes to kernel memory in the #VC handler. Fixes: 5e3427a7bc432 ("x86/sev-es: Handle instruction fetches from user-space") Signed-off-by: Joerg Roedel Signed-off-by: Borislav Petkov Cc: stable@vger.kernel.org # v5.10+ Link: https://lkml.kernel.org/r/20210303141716.29223-6-joro@8bytes.org --- arch/x86/include/asm/insn-eval.h | 2 +- arch/x86/kernel/sev-es.c | 2 +- arch/x86/lib/insn-eval.c | 66 ++++++++++++++++++++++++------- 3 files changed, 55 insertions(+), 15 deletions(-) diff --git a/arch/x86/include/asm/insn-eval.h b/arch/x86/include/asm/insn-eval.h index a0f839a..98b4dae 100644 --- a/arch/x86/include/asm/insn-eval.h +++ b/arch/x86/include/asm/insn-eval.h @@ -23,6 +23,8 @@ unsigned long insn_get_seg_base(struct pt_regs *regs, int seg_reg_idx); int insn_get_code_seg_params(struct pt_regs *regs); int insn_fetch_from_user(struct pt_regs *regs, unsigned char buf[MAX_INSN_SIZE]); +int insn_fetch_from_user_inatomic(struct pt_regs *regs, + unsigned char buf[MAX_INSN_SIZE]); bool insn_decode(struct insn *insn, struct pt_regs *regs, unsigned char buf[MAX_INSN_SIZE], int buf_size); diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c index c3fd8fa..04a780a 100644 --- a/arch/x86/kernel/sev-es.c +++ b/arch/x86/kernel/sev-es.c @@ -258,7 +258,7 @@ static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt) int res; if (user_mode(ctxt->regs)) { - res = insn_fetch_from_user(ctxt->regs, buffer); + res = insn_fetch_from_user_inatomic(ctxt->regs, buffer); if (!res) { ctxt->fi.vector = X86_TRAP_PF; ctxt->fi.error_code = X86_PF_INSTR | X86_PF_USER; diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c index 4229950..bb0b3fe 100644 --- a/arch/x86/lib/insn-eval.c +++ b/arch/x86/lib/insn-eval.c @@ -1415,6 +1415,25 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs) } } +static unsigned long insn_get_effective_ip(struct pt_regs *regs) +{ + unsigned long seg_base = 0; + + /* + * If not in user-space long mode, a custom code segment could be in + * use. This is true in protected mode (if the process defined a local + * descriptor table), or virtual-8086 mode. In most of the cases + * seg_base will be zero as in USER_CS. + */ + if (!user_64bit_mode(regs)) { + seg_base = insn_get_seg_base(regs, INAT_SEG_REG_CS); + if (seg_base == -1L) + return 0; + } + + return seg_base + regs->ip; +} + /** * insn_fetch_from_user() - Copy instruction bytes from user-space memory * @regs: Structure with register values as seen when entering kernel mode @@ -1431,24 +1450,43 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs) */ int insn_fetch_from_user(struct pt_regs *regs, unsigned char buf[MAX_INSN_SIZE]) { - unsigned long seg_base = 0; + unsigned long ip; int not_copied; - /* - * If not in user-space long mode, a custom code segment could be in - * use. This is true in protected mode (if the process defined a local - * descriptor table), or virtual-8086 mode. In most of the cases - * seg_base will be zero as in USER_CS. - */ - if (!user_64bit_mode(regs)) { - seg_base = insn_get_seg_base(regs, INAT_SEG_REG_CS); - if (seg_base == -1L) - return 0; - } + ip = insn_get_effective_ip(regs); + if (!ip) + return 0; + + not_copied = copy_from_user(buf, (void __user *)ip, MAX_INSN_SIZE); + return MAX_INSN_SIZE - not_copied; +} + +/** + * insn_fetch_from_user_inatomic() - Copy instruction bytes from user-space memory + * while in atomic code + * @regs: Structure with register values as seen when entering kernel mode + * @buf: Array to store the fetched instruction + * + * Gets the linear address of the instruction and copies the instruction bytes + * to the buf. This function must be used in atomic context. + * + * Returns: + * + * Number of instruction bytes copied. + * + * 0 if nothing was copied. + */ +int insn_fetch_from_user_inatomic(struct pt_regs *regs, unsigned char buf[MAX_INSN_SIZE]) +{ + unsigned long ip; + int not_copied; + + ip = insn_get_effective_ip(regs); + if (!ip) + return 0; - not_copied = copy_from_user(buf, (void __user *)(seg_base + regs->ip), - MAX_INSN_SIZE); + not_copied = __copy_from_user_inatomic(buf, (void __user *)ip, MAX_INSN_SIZE); return MAX_INSN_SIZE - not_copied; }