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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 18EFAC433E0 for ; Wed, 27 Jan 2021 11:08:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B284320739 for ; Wed, 27 Jan 2021 11:08:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236342AbhA0LHi (ORCPT ); Wed, 27 Jan 2021 06:07:38 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57226 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234787AbhA0LGQ (ORCPT ); Wed, 27 Jan 2021 06:06:16 -0500 Received: from mail-pf1-x430.google.com (mail-pf1-x430.google.com [IPv6:2607:f8b0:4864:20::430]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BC048C061573 for ; Wed, 27 Jan 2021 03:05:32 -0800 (PST) Received: by mail-pf1-x430.google.com with SMTP id u67so971262pfb.3 for ; Wed, 27 Jan 2021 03:05:32 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id; bh=f0uhIYxEP5ACLreEqbTzuHdyKnahqQMCK2iaOeXStuE=; b=btrRant1sIf03uhv12RjQI0X/QiKi+FgI519vip/U3v42feIFdMnIzoYnOULiP+35/ 7riP0hml+kY1DxPQAeJakolmkDIPOosMGIkg6bxRMdK+RNBAF5lo0KWiX3x4W8An4wgJ ezZE7UaUlGCo57NqtpH65llxh5MLdyY3mEFoDgA1qS13rPRar9mtc9KNVeCXdEvFREsI 6DmyfzmhY7HwFPpF9O2xNza4/ejHLsr8N/wgn4++85NxUN6OHI0kdsJGijajw70NITWB 9G6BA3DlKw4dtnlaEedT9gVk/g1N3ApeWkuGnTvf4MoI2PlkVLFWiy3T0j1flvNh84Zt JBiA== 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; bh=f0uhIYxEP5ACLreEqbTzuHdyKnahqQMCK2iaOeXStuE=; b=hepcygtg7Us1coVNE4SlLfU/348pWsKxyVsDgP79HsF0F5vwsVhGDYPKoHFCc1etrN EQiuknSg4dsWRx/c2t4Oer8jjlX2OocTE/4hB6mBsbgI9z4aakdOGjBU6KtjoH+vop1q kHmkov6/FHI6FvF0CaDrKWiiSxqa7amPskqigPjMxaBqbLCxoGXVA9u5UqFhbACB+GA6 Br2AHimu7WTAMQ1j0Vj7XsY0T1rD0hChDVmKqH9ZrFE+ZyssNHwSzZyds7Kkw5h/bpP9 vYjkJdy12qN+6nm5Wub3ua3EokwOPx8zShMwiBdY6xpQN01NQZD6BR3RsnPPxBtoTA9k Awpw== X-Gm-Message-State: AOAM533MjiydblgGTTeMWFsFRyCOhxoMsHnOCgmSVpU8g+cMAdJNa/X1 l33CJEOGFiNO5SpC4NdaO+8= X-Google-Smtp-Source: ABdhPJzWvJDVcfQ1pXKDcsGk/OYJBVPeO0D0UYsnE8vQFikUGuNZI+SdRW1qVWMuczVGCeQ3sY2lhA== X-Received: by 2002:a65:6152:: with SMTP id o18mr10783532pgv.392.1611745532399; Wed, 27 Jan 2021 03:05:32 -0800 (PST) Received: from bj04616pcu01.spreadtrum.com ([117.18.48.82]) by smtp.gmail.com with ESMTPSA id o190sm2184433pga.2.2021.01.27.03.05.27 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 27 Jan 2021 03:05:31 -0800 (PST) From: Candle Sun To: keescook@chromium.org Cc: arnd@arndb.de, gregkh@linuxfoundation.org, natechancellor@gmail.com, ndesaulniers@google.com, candle.sun@unisoc.com, David.Laight@aculab.com, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com Subject: [PATCH v2] lkdtm: fix memory copy size for WRITE_KERN Date: Wed, 27 Jan 2021 19:05:10 +0800 Message-Id: <20210127110510.24492-1-candlesea@gmail.com> X-Mailer: git-send-email 2.17.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Candle Sun Though do_overwritten() follows do_nothing() in source code, the final memory address order is determined by compiler. We can't always assume address of do_overwritten() is bigger than do_nothing(). At least the Clang we are using places do_overwritten() before do_nothing() in the object. This causes the copy size in lkdtm_WRITE_KERN() is *really* big and WRITE_KERN test on ARM32 arch will fail. Get absolute value of the address substraction for memcpy() size. Signed-off-by: Candle Sun --- Changes in v2: - Use abs() in place of address comparison. --- drivers/misc/lkdtm/perms.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c index 2dede2ef658f..fbb7f4554054 100644 --- a/drivers/misc/lkdtm/perms.c +++ b/drivers/misc/lkdtm/perms.c @@ -31,13 +31,13 @@ static unsigned long ro_after_init __ro_after_init = 0x55AA5500; * This just returns to the caller. It is designed to be copied into * non-executable memory regions. */ -static void do_nothing(void) +static noinline void do_nothing(void) { return; } /* Must immediately follow do_nothing for size calculuations to work out. */ -static void do_overwritten(void) +static noinline void do_overwritten(void) { pr_info("do_overwritten wasn't overwritten!\n"); return; @@ -113,7 +113,7 @@ void lkdtm_WRITE_KERN(void) size_t size; volatile unsigned char *ptr; - size = (unsigned long)do_overwritten - (unsigned long)do_nothing; + size = (size_t)abs((uintptr_t)do_overwritten - (uintptr_t)do_nothing); ptr = (unsigned char *)do_overwritten; pr_info("attempting bad %zu byte write at %px\n", size, ptr); -- 2.17.0