From patchwork Sun Oct 17 12:38:25 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christophe Leroy X-Patchwork-Id: 12564215 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 A8C0BC433FE for ; Sun, 17 Oct 2021 12:39:29 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5B51B61054 for ; Sun, 17 Oct 2021 12:39:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 5B51B61054 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=csgroup.eu Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 0137C6B007D; Sun, 17 Oct 2021 08:39:29 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id F03BE6B007E; Sun, 17 Oct 2021 08:39:28 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E1A0A6B0080; Sun, 17 Oct 2021 08:39:28 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0088.hostedemail.com [216.40.44.88]) by kanga.kvack.org (Postfix) with ESMTP id CF05E6B007D for ; Sun, 17 Oct 2021 08:39:28 -0400 (EDT) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 8E2E81802E6FD for ; Sun, 17 Oct 2021 12:39:28 +0000 (UTC) X-FDA: 78705885216.01.3DE8206 Received: from pegase2.c-s.fr (pegase2.c-s.fr [93.17.235.10]) by imf05.hostedemail.com (Postfix) with ESMTP id DB8A4507D4C5 for ; Sun, 17 Oct 2021 12:39:24 +0000 (UTC) Received: from localhost (mailhub3.si.c-s.fr [172.26.127.67]) by localhost (Postfix) with ESMTP id 4HXKM722jdz9sSg; Sun, 17 Oct 2021 14:39:15 +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 iafKGYbDE3MR; Sun, 17 Oct 2021 14:39:15 +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 4HXKM00rflz9sSn; Sun, 17 Oct 2021 14:39:08 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id EFA648B76C; Sun, 17 Oct 2021 14:39:07 +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 djCpVe6IlRcj; Sun, 17 Oct 2021 14:39:07 +0200 (CEST) Received: from PO20335.IDSI0.si.c-s.fr (unknown [192.168.203.38]) by messagerie.si.c-s.fr (Postfix) with ESMTP id DB17C8B779; Sun, 17 Oct 2021 14:39:06 +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 19HCcuUq2946777 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Sun, 17 Oct 2021 14:38:56 +0200 Received: (from chleroy@localhost) by PO20335.IDSI0.si.c-s.fr (8.16.1/8.16.1/Submit) id 19HCcu6C2946776; Sun, 17 Oct 2021 14:38:56 +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 v3 12/12] lkdtm: Add a test for function descriptors protection Date: Sun, 17 Oct 2021 14:38:25 +0200 Message-Id: <67f9545c9ad15048bfe0104278ef9595d051dbc8.1634457599.git.christophe.leroy@csgroup.eu> 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=1634474304; l=2771; s=20211009; h=from:subject:message-id; bh=cWdjG38iugbNn7Oiz2TreaAGM7Xs+ytxo1CCxP92MAo=; b=CNzYSDXWVeyn10qO31zmLFLqeJNSq+stusBu8TKL94x+HMvBknQNoODkUykR1D9bR1UxlR9ps9p6 qmtDMf+oD3vgpYPIVeTR/2E4Foa237QF4B9e3ry9ADug1+xSLvoH X-Developer-Key: i=christophe.leroy@csgroup.eu; a=ed25519; pk=HIzTzUj91asvincQGOFx6+ZF5AoUuP9GdOtQChs7Mm0= X-Rspamd-Queue-Id: DB8A4507D4C5 Authentication-Results: imf05.hostedemail.com; dkim=none; spf=pass (imf05.hostedemail.com: domain of christophe.leroy@csgroup.eu designates 93.17.235.10 as permitted sender) smtp.mailfrom=christophe.leroy@csgroup.eu; dmarc=none X-Stat-Signature: 85477kjyootu3k3rw147ps9prqwg31zr X-Rspamd-Server: rspam05 X-HE-Tag: 1634474364-859400 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Add WRITE_OPD to check that you can't modify function descriptors. Gives the following result when function descriptors are not protected: lkdtm: Performing direct entry WRITE_OPD lkdtm: attempting bad 16 bytes write at c00000000269b358 lkdtm: FAIL: survived bad write lkdtm: do_nothing was hijacked! Looks like a standard compiler barrier() is not enough to force GCC to use the modified function descriptor. Had to add a fake empty inline assembly to force GCC to reload the function descriptor. Signed-off-by: Christophe Leroy Acked-by: Kees Cook --- drivers/misc/lkdtm/core.c | 1 + drivers/misc/lkdtm/lkdtm.h | 1 + drivers/misc/lkdtm/perms.c | 22 ++++++++++++++++++++++ 3 files changed, 24 insertions(+) diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c index fe6fd34b8caf..de092aa03b5d 100644 --- a/drivers/misc/lkdtm/core.c +++ b/drivers/misc/lkdtm/core.c @@ -148,6 +148,7 @@ static const struct crashtype crashtypes[] = { CRASHTYPE(WRITE_RO), CRASHTYPE(WRITE_RO_AFTER_INIT), CRASHTYPE(WRITE_KERN), + CRASHTYPE(WRITE_OPD), CRASHTYPE(REFCOUNT_INC_OVERFLOW), CRASHTYPE(REFCOUNT_ADD_OVERFLOW), CRASHTYPE(REFCOUNT_INC_NOT_ZERO_OVERFLOW), diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h index c212a253edde..188bd0fd6575 100644 --- a/drivers/misc/lkdtm/lkdtm.h +++ b/drivers/misc/lkdtm/lkdtm.h @@ -105,6 +105,7 @@ void __init lkdtm_perms_init(void); void lkdtm_WRITE_RO(void); void lkdtm_WRITE_RO_AFTER_INIT(void); void lkdtm_WRITE_KERN(void); +void lkdtm_WRITE_OPD(void); void lkdtm_EXEC_DATA(void); void lkdtm_EXEC_STACK(void); void lkdtm_EXEC_KMALLOC(void); diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c index 1cf24c4a79e9..2c6aba3ff32b 100644 --- a/drivers/misc/lkdtm/perms.c +++ b/drivers/misc/lkdtm/perms.c @@ -44,6 +44,11 @@ static noinline void do_overwritten(void) return; } +static noinline void do_almost_nothing(void) +{ + pr_info("do_nothing was hijacked!\n"); +} + static void *setup_function_descriptor(func_desc_t *fdesc, void *dst) { if (!have_function_descriptors()) @@ -144,6 +149,23 @@ void lkdtm_WRITE_KERN(void) do_overwritten(); } +void lkdtm_WRITE_OPD(void) +{ + size_t size = sizeof(func_desc_t); + void (*func)(void) = do_nothing; + + if (!have_function_descriptors()) { + pr_info("XFAIL: Platform doesn't use function descriptors.\n"); + return; + } + pr_info("attempting bad %zu bytes write at %px\n", size, do_nothing); + memcpy(do_nothing, do_almost_nothing, size); + pr_err("FAIL: survived bad write\n"); + + asm("" : "=m"(func)); + func(); +} + void lkdtm_EXEC_DATA(void) { execute_location(data_area, CODE_WRITE);