From patchwork Thu Oct 14 05:49:59 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christophe Leroy X-Patchwork-Id: 12557801 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C7BE8C4332F for ; Thu, 14 Oct 2021 06:24:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B271D600CC for ; Thu, 14 Oct 2021 06:24:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230040AbhJNG0M (ORCPT ); Thu, 14 Oct 2021 02:26:12 -0400 Received: from pegase2.c-s.fr ([93.17.235.10]:45337 "EHLO pegase2.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229883AbhJNG0J (ORCPT ); Thu, 14 Oct 2021 02:26:09 -0400 Received: from localhost (mailhub3.si.c-s.fr [172.26.127.67]) by localhost (Postfix) with ESMTP id 4HVK9W17yZz9sSZ; Thu, 14 Oct 2021 08:23:59 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from pegase2.c-s.fr ([172.26.127.65]) by localhost (pegase2.c-s.fr [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id b0yiiAEuME1g; Thu, 14 Oct 2021 08:23:59 +0200 (CEST) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase2.c-s.fr (Postfix) with ESMTP id 4HVK9V5Kd0z9sSK; Thu, 14 Oct 2021 08:23:58 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id A0AB98B788; Thu, 14 Oct 2021 08:23:58 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id gzQ4S7fKJNqd; Thu, 14 Oct 2021 08:23:58 +0200 (CEST) Received: from PO20335.IDSI0.si.c-s.fr (unknown [192.168.202.231]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 402468B763; Thu, 14 Oct 2021 08:23:58 +0200 (CEST) Received: from PO20335.IDSI0.si.c-s.fr (localhost [127.0.0.1]) by PO20335.IDSI0.si.c-s.fr (8.16.1/8.16.1) with ESMTPS id 19E5oQAt2266034 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Thu, 14 Oct 2021 07:50:26 +0200 Received: (from chleroy@localhost) by PO20335.IDSI0.si.c-s.fr (8.16.1/8.16.1/Submit) id 19E5oQZE2266033; Thu, 14 Oct 2021 07:50:26 +0200 X-Authentication-Warning: PO20335.IDSI0.si.c-s.fr: chleroy set sender to christophe.leroy@csgroup.eu using -f From: Christophe Leroy To: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Andrew Morton , "James E.J. Bottomley" , Helge Deller , Arnd Bergmann , Kees Cook , Greg Kroah-Hartman Cc: Christophe Leroy , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-ia64@vger.kernel.org, linux-parisc@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v2 10/13] lkdtm: Really write into kernel text in WRITE_KERN Date: Thu, 14 Oct 2021 07:49:59 +0200 Message-Id: X-Mailer: git-send-email 2.31.1 In-Reply-To: References: MIME-Version: 1.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1634190596; l=1853; s=20211009; h=from:subject:message-id; bh=z/aB80p6e37+wi5UDvnOtBLSSHNpIOGfxrnndLg8VIY=; b=GzlSY84BycesIyXqAb04qiQPImy6tCuMMcp0B+fXkd/gAdogGCmqQ6ckrRhiRM1oHHrRbc5xqrwJ XthU1P3yCgyO/6hVvrBos8Ex6ZO+uKbuqQWMpiahdoI2ATxn/Ysb X-Developer-Key: i=christophe.leroy@csgroup.eu; a=ed25519; pk=HIzTzUj91asvincQGOFx6+ZF5AoUuP9GdOtQChs7Mm0= Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org WRITE_KERN is supposed to overwrite some kernel text, namely do_overwritten() function. But at the time being it overwrites do_overwritten() function descriptor, not function text. Fix it by dereferencing the function descriptor to obtain function text pointer. And make do_overwritten() noinline so that it is really do_overwritten() which is called by lkdtm_WRITE_KERN(). Acked-by: Kees Cook Signed-off-by: Christophe Leroy --- drivers/misc/lkdtm/perms.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c index 60b3b2fe929d..035fcca441f0 100644 --- a/drivers/misc/lkdtm/perms.c +++ b/drivers/misc/lkdtm/perms.c @@ -10,6 +10,7 @@ #include #include #include +#include /* Whether or not to fill the target memory area with do_nothing(). */ #define CODE_WRITE true @@ -37,7 +38,7 @@ static noinline void do_nothing(void) } /* 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; @@ -113,8 +114,9 @@ void lkdtm_WRITE_KERN(void) size_t size; volatile unsigned char *ptr; - size = (unsigned long)do_overwritten - (unsigned long)do_nothing; - ptr = (unsigned char *)do_overwritten; + size = (unsigned long)dereference_function_descriptor(do_overwritten) - + (unsigned long)dereference_function_descriptor(do_nothing); + ptr = dereference_function_descriptor(do_overwritten); pr_info("attempting bad %zu byte write at %px\n", size, ptr); memcpy((void *)ptr, (unsigned char *)do_nothing, size);