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=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,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 B5CABC4742C for ; Mon, 16 Nov 2020 14:50:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 301F122447 for ; Mon, 16 Nov 2020 14:50:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=privacyrequired.com header.i=@privacyrequired.com header.b="UGZldpm2" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729964AbgKPOuj (ORCPT ); Mon, 16 Nov 2020 09:50:39 -0500 Received: from devianza.investici.org ([198.167.222.108]:26963 "EHLO devianza.investici.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729438AbgKPOuj (ORCPT ); Mon, 16 Nov 2020 09:50:39 -0500 Received: from mx2.investici.org (unknown [127.0.0.1]) by devianza.investici.org (Postfix) with ESMTP id 4CZX7K43lLz6vMd; Mon, 16 Nov 2020 14:50:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=privacyrequired.com; s=stigmate; t=1605538237; bh=v2/DaV8STEEMs9x+B77A7l6psuLVf/YLdYQGCG8Qjcg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UGZldpm2HcciQOQQQzd4+if+mmKbJc7wDGKK5HkI+N/Z1o7F9DfkZ5HmKK6Ci2f6e OOIBMTQ5hjTK5vRMu/hgLXqWSA81suaf4jVb4S0JmUuq/Yu395j4IM2OV9MlmuvA9S ys6P0Yzgz8plB9+PZPCbVC2Fs+7USXFA2GJAlDxU= Received: from [198.167.222.108] (mx2.investici.org [198.167.222.108]) (Authenticated sender: laniel_francis@privacyrequired.com) by localhost (Postfix) with ESMTPSA id 4CZX7K2JVYz6vMX; Mon, 16 Nov 2020 14:50:37 +0000 (UTC) From: laniel_francis@privacyrequired.com To: linux-hardening@vger.kernel.org Cc: dja@axtens.net, keescook@chromium.org Subject: [PATCH v4 2/5] lkdtm: tests for FORTIFY_SOURCE Date: Mon, 16 Nov 2020 15:50:09 +0100 Message-Id: <20201116145012.24471-3-laniel_francis@privacyrequired.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20201116145012.24471-1-laniel_francis@privacyrequired.com> References: <20201116145012.24471-1-laniel_francis@privacyrequired.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org From: Daniel Axtens Add code to test both: - runtime detection of the overrun of a structure. This covers the __builtin_object_size(x, 0) case. This test is called FORTIFY_OBJECT. - runtime detection of the overrun of a char array within a structure. This covers the __builtin_object_size(x, 1) case which can be used for some string functions. This test is called FORTIFY_SUBOBJECT. Suggested-by: Kees Cook Reviewed-by: Kees Cook Signed-off-by: Daniel Axtens --- drivers/misc/lkdtm/bugs.c | 50 ++++++++++++++++++++++++++++++++++++++ drivers/misc/lkdtm/core.c | 2 ++ drivers/misc/lkdtm/lkdtm.h | 2 ++ 3 files changed, 54 insertions(+) diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c index a0675d4154d2..110f5a8538e9 100644 --- a/drivers/misc/lkdtm/bugs.c +++ b/drivers/misc/lkdtm/bugs.c @@ -482,3 +482,53 @@ noinline void lkdtm_CORRUPT_PAC(void) pr_err("XFAIL: this test is arm64-only\n"); #endif } + +void lkdtm_FORTIFY_OBJECT(void) +{ + struct target { + char a[10]; + } target[2] = {}; + int result; + + /* + * Using volatile prevents the compiler from determining the value of + * 'size' at compile time. Without that, we would get a compile error + * rather than a runtime error. + */ + volatile int size = 11; + + pr_info("trying to read past the end of a struct\n"); + + result = memcmp(&target[0], &target[1], size); + + /* Print result to prevent the code from being eliminated */ + pr_err("FAIL: fortify did not catch an object overread!\n" + "\"%d\" was the memcmp result.\n", result); +} + +void lkdtm_FORTIFY_SUBOBJECT(void) +{ + struct target { + char a[10]; + char b[10]; + } target; + char *src; + + src = kmalloc(20, GFP_KERNEL); + strscpy(src, "over ten bytes", 20); + + pr_info("trying to strcpy past the end of a member of a struct\n"); + + /* + * strncpy(target.a, src, 20); will hit a compile error because the + * compiler knows at build time that target.a < 20 bytes. Use strcpy() + * to force a runtime error. + */ + strcpy(target.a, src); + + /* Use target.a to prevent the code from being eliminated */ + pr_err("FAIL: fortify did not catch an sub-object overrun!\n" + "\"%s\" was copied.\n", target.a); + + kfree(src); +} diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c index 97803f213d9d..b8c51a633fcc 100644 --- a/drivers/misc/lkdtm/core.c +++ b/drivers/misc/lkdtm/core.c @@ -117,6 +117,8 @@ static const struct crashtype crashtypes[] = { CRASHTYPE(UNSET_SMEP), CRASHTYPE(CORRUPT_PAC), CRASHTYPE(UNALIGNED_LOAD_STORE_WRITE), + CRASHTYPE(FORTIFY_OBJECT), + CRASHTYPE(FORTIFY_SUBOBJECT), CRASHTYPE(OVERWRITE_ALLOCATION), CRASHTYPE(WRITE_AFTER_FREE), CRASHTYPE(READ_AFTER_FREE), diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h index 6dec4c9b442f..49e6b945feb7 100644 --- a/drivers/misc/lkdtm/lkdtm.h +++ b/drivers/misc/lkdtm/lkdtm.h @@ -32,6 +32,8 @@ void lkdtm_STACK_GUARD_PAGE_TRAILING(void); void lkdtm_UNSET_SMEP(void); void lkdtm_DOUBLE_FAULT(void); void lkdtm_CORRUPT_PAC(void); +void lkdtm_FORTIFY_OBJECT(void); +void lkdtm_FORTIFY_SUBOBJECT(void); /* lkdtm_heap.c */ void __init lkdtm_heap_init(void); -- 2.20.1