From patchwork Fri Apr 26 23:23:01 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nadav Amit X-Patchwork-Id: 10919973 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 8689014B6 for ; Sat, 27 Apr 2019 06:43:59 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7663128E6B for ; Sat, 27 Apr 2019 06:43:59 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6A73D28E7C; Sat, 27 Apr 2019 06:43:59 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.5 required=2.0 tests=BAYES_00,DATE_IN_PAST_06_12, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FROM,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 12AE928E6B for ; Sat, 27 Apr 2019 06:43:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726824AbfD0Gnx (ORCPT ); Sat, 27 Apr 2019 02:43:53 -0400 Received: from mail-pg1-f193.google.com ([209.85.215.193]:38018 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726663AbfD0Gng (ORCPT ); Sat, 27 Apr 2019 02:43:36 -0400 Received: by mail-pg1-f193.google.com with SMTP id j26so2630779pgl.5; Fri, 26 Apr 2019 23:43:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=Mq726et3FUsm8L5SG93p+KUhd7ShOgthVM8qUN29ytY=; b=ZcHDpG5oI881U7Ra0/L2O5huO2cwDn2YrdsQ5hiAWkm6WdBzN67nlkJvfLDLJC5q+X UOCeP+9RydbCT4dO6iGp4lZQdm3+sXHNSQC0G0grGB6NOlnyKbwZn5NdDqZwDHIXRDud 3mNZu1J6RFiZozyuuSJ7f0wBAoiYQFhmUfj5tGkTm8jduQKjEFGn6AF04k5qQYjIWsXY 4YzLX+ZgfiYxaYFVUDUXXbJdfkkMMJKkcbeIB+VGTLlKKEI2dS4TTD29m/lBt3TdxyYa a4fp8LYLp6QEbTAIinVcBUAwlwg+TwtnzyGC3pPfhsUXM3/E24y9pQ9Ah5nWVdchzhK2 LMJw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=Mq726et3FUsm8L5SG93p+KUhd7ShOgthVM8qUN29ytY=; b=bGF4oNImy9xNe8NZH9foiS8upuxXKgS4qSzGlTeFBNrLl27nHbGXv8Io5bM1tqdzDL vGEQiMJ6yQIcQc6jkiJf1WyQdeg/tfBJ/3puaZPk2XO74UezsL8nMeWoqc8Tx4KBRwnd CPyq9ljeWzfvVvx5COZao1KrFbTUbdTnp02cuDP/zf8uBA+S9Z4iY+BzFyN/2jMF2EVs FOv3Rx7Wu0LeDsb09j8JkNB5H3qErpNTKgauWKktz2iikoXjGj8Fj60x+1grSPW28tBW h8hMVmrNxBt7LFINkMNz2ddxeXdhNpelCwI6VZx8hcr9dphqArVf1VPWgVAsKQzHDiBB cYMQ== X-Gm-Message-State: APjAAAXSE+zDMZn2L7+YO0b/FA94QvvMnNA3ZoxppUIlYZ5hgDTkEvaD to3BcGP1GLRfcUzYuUbPa1g= X-Google-Smtp-Source: APXvYqz6QdLKu0nIIJYQFhptNQ/c9BRHYqidvmm2brorovTM3Ggu9E591UYxGE1lKlV0dGgfmeOtWg== X-Received: by 2002:a63:e051:: with SMTP id n17mr5092049pgj.19.1556347415619; Fri, 26 Apr 2019 23:43:35 -0700 (PDT) Received: from sc2-haas01-esx0118.eng.vmware.com ([66.170.99.1]) by smtp.gmail.com with ESMTPSA id j22sm36460145pfn.129.2019.04.26.23.43.34 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 26 Apr 2019 23:43:35 -0700 (PDT) From: nadav.amit@gmail.com To: Peter Zijlstra , Borislav Petkov , Andy Lutomirski , Ingo Molnar Cc: linux-kernel@vger.kernel.org, x86@kernel.org, hpa@zytor.com, Thomas Gleixner , Nadav Amit , Dave Hansen , linux_dti@icloud.com, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, akpm@linux-foundation.org, kernel-hardening@lists.openwall.com, linux-mm@kvack.org, will.deacon@arm.com, ard.biesheuvel@linaro.org, kristen@linux.intel.com, deneen.t.dock@intel.com, Rick Edgecombe , Nadav Amit , Masami Hiramatsu Subject: [PATCH v6 22/24] x86/alternative: Comment about module removal races Date: Fri, 26 Apr 2019 16:23:01 -0700 Message-Id: <20190426232303.28381-23-nadav.amit@gmail.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190426232303.28381-1-nadav.amit@gmail.com> References: <20190426232303.28381-1-nadav.amit@gmail.com> Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP From: Nadav Amit Add a comment to clarify that users of text_poke() must ensure that no races with module removal take place. Cc: Masami Hiramatsu Signed-off-by: Nadav Amit Signed-off-by: Rick Edgecombe --- arch/x86/kernel/alternative.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 18f959975ea0..7b9b49dfc05a 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -810,6 +810,11 @@ static void *__text_poke(void *addr, const void *opcode, size_t len) * It means the size must be writable atomically and the address must be aligned * in a way that permits an atomic write. It also makes sure we fit on a single * page. + * + * Note that the caller must ensure that if the modified code is part of a + * module, the module would not be removed during poking. This can be achieved + * by registering a module notifier, and ordering module removal and patching + * trough a mutex. */ void *text_poke(void *addr, const void *opcode, size_t len) {