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,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 9D863C433E1 for ; Mon, 17 Aug 2020 19:37:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 823A620716 for ; Mon, 17 Aug 2020 19:37:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597693026; bh=XM8gBrncBcsEvtN6xf7AmQVtU5Ud4TI5sZIESDwmbD0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=kfVA5AFPOsHMxM+OnXyzxlTW5+py++LinMFaO7LThdz8Jk3Ca8H43Oedxev70w7Yh aPuUxWFjGweqMZV9MznPvqIUUuwKXoVGjaFyqi/fkI2uoYeLqo5/sU+fO51ib5813X 4KYBuSMk1vmxT7K/xb6d/hoAyx8ugKCcyShYRhIE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729810AbgHQP2K (ORCPT ); Mon, 17 Aug 2020 11:28:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:41968 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730004AbgHQP2J (ORCPT ); Mon, 17 Aug 2020 11:28:09 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 598B723ABA; Mon, 17 Aug 2020 15:28:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597678088; bh=XM8gBrncBcsEvtN6xf7AmQVtU5Ud4TI5sZIESDwmbD0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=AE1TJDKeHZxQej18WCKAw9nTktOGIHoT/mIfgLdNAob7VAGNqrAA71p2ieIkMtMK3 nwfevS8KYRIHrw/0wPnkKEzEvOz49xbLqPGe0X2AH6TCPbomqQE8mqgTly4GfluUf2 jI8nzzXOK2aLIU8GwvPtXRymcuV9sHAHMFcy9i2Q= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Prasad Sodagudi , Sami Tolvanen , Kees Cook , Sasha Levin Subject: [PATCH 5.8 187/464] lkdtm: Avoid more compiler optimizations for bad writes Date: Mon, 17 Aug 2020 17:12:20 +0200 Message-Id: <20200817143842.780098167@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200817143833.737102804@linuxfoundation.org> References: <20200817143833.737102804@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Kees Cook [ Upstream commit 464e86b4abadfc490f426954b431e2ec6a9d7bd2 ] It seems at least Clang is able to throw away writes it knows are destined for read-only memory, which makes things like the WRITE_RO test fail, as the write gets elided. Instead, force the variable to be volatile, and make similar changes through-out other tests in an effort to avoid needing to repeat fixing these kinds of problems. Also includes pr_err() calls in failure paths so that kernel logs are more clear in the failure case. Reported-by: Prasad Sodagudi Suggested-by: Sami Tolvanen Fixes: 9ae113ce5faf ("lkdtm: add tests for additional page permissions") Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20200625203704.317097-2-keescook@chromium.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/misc/lkdtm/bugs.c | 11 +++++------ drivers/misc/lkdtm/perms.c | 22 +++++++++++++++------- drivers/misc/lkdtm/usercopy.c | 7 +++++-- 3 files changed, 25 insertions(+), 15 deletions(-) diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c index 736675f0a2464..08c70281c380e 100644 --- a/drivers/misc/lkdtm/bugs.c +++ b/drivers/misc/lkdtm/bugs.c @@ -118,9 +118,8 @@ noinline void lkdtm_CORRUPT_STACK(void) /* Use default char array length that triggers stack protection. */ char data[8] __aligned(sizeof(void *)); - __lkdtm_CORRUPT_STACK(&data); - - pr_info("Corrupted stack containing char array ...\n"); + pr_info("Corrupting stack containing char array ...\n"); + __lkdtm_CORRUPT_STACK((void *)&data); } /* Same as above but will only get a canary with -fstack-protector-strong */ @@ -131,9 +130,8 @@ noinline void lkdtm_CORRUPT_STACK_STRONG(void) unsigned long *ptr; } data __aligned(sizeof(void *)); - __lkdtm_CORRUPT_STACK(&data); - - pr_info("Corrupted stack containing union ...\n"); + pr_info("Corrupting stack containing union ...\n"); + __lkdtm_CORRUPT_STACK((void *)&data); } void lkdtm_UNALIGNED_LOAD_STORE_WRITE(void) @@ -248,6 +246,7 @@ void lkdtm_ARRAY_BOUNDS(void) kfree(not_checked); kfree(checked); + pr_err("FAIL: survived array bounds overflow!\n"); } void lkdtm_CORRUPT_LIST_ADD(void) diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c index 62f76d506f040..2dede2ef658f3 100644 --- a/drivers/misc/lkdtm/perms.c +++ b/drivers/misc/lkdtm/perms.c @@ -57,6 +57,7 @@ static noinline void execute_location(void *dst, bool write) } pr_info("attempting bad execution at %px\n", func); func(); + pr_err("FAIL: func returned\n"); } static void execute_user_location(void *dst) @@ -75,20 +76,22 @@ static void execute_user_location(void *dst) return; pr_info("attempting bad execution at %px\n", func); func(); + pr_err("FAIL: func returned\n"); } void lkdtm_WRITE_RO(void) { - /* Explicitly cast away "const" for the test. */ - unsigned long *ptr = (unsigned long *)&rodata; + /* Explicitly cast away "const" for the test and make volatile. */ + volatile unsigned long *ptr = (unsigned long *)&rodata; pr_info("attempting bad rodata write at %px\n", ptr); *ptr ^= 0xabcd1234; + pr_err("FAIL: survived bad write\n"); } void lkdtm_WRITE_RO_AFTER_INIT(void) { - unsigned long *ptr = &ro_after_init; + volatile unsigned long *ptr = &ro_after_init; /* * Verify we were written to during init. Since an Oops @@ -102,19 +105,21 @@ void lkdtm_WRITE_RO_AFTER_INIT(void) pr_info("attempting bad ro_after_init write at %px\n", ptr); *ptr ^= 0xabcd1234; + pr_err("FAIL: survived bad write\n"); } void lkdtm_WRITE_KERN(void) { size_t size; - unsigned char *ptr; + volatile unsigned char *ptr; size = (unsigned long)do_overwritten - (unsigned long)do_nothing; ptr = (unsigned char *)do_overwritten; pr_info("attempting bad %zu byte write at %px\n", size, ptr); - memcpy(ptr, (unsigned char *)do_nothing, size); + memcpy((void *)ptr, (unsigned char *)do_nothing, size); flush_icache_range((unsigned long)ptr, (unsigned long)(ptr + size)); + pr_err("FAIL: survived bad write\n"); do_overwritten(); } @@ -193,9 +198,11 @@ void lkdtm_ACCESS_USERSPACE(void) pr_info("attempting bad read at %px\n", ptr); tmp = *ptr; tmp += 0xc0dec0de; + pr_err("FAIL: survived bad read\n"); pr_info("attempting bad write at %px\n", ptr); *ptr = tmp; + pr_err("FAIL: survived bad write\n"); vm_munmap(user_addr, PAGE_SIZE); } @@ -203,19 +210,20 @@ void lkdtm_ACCESS_USERSPACE(void) void lkdtm_ACCESS_NULL(void) { unsigned long tmp; - unsigned long *ptr = (unsigned long *)NULL; + volatile unsigned long *ptr = (unsigned long *)NULL; pr_info("attempting bad read at %px\n", ptr); tmp = *ptr; tmp += 0xc0dec0de; + pr_err("FAIL: survived bad read\n"); pr_info("attempting bad write at %px\n", ptr); *ptr = tmp; + pr_err("FAIL: survived bad write\n"); } void __init lkdtm_perms_init(void) { /* Make sure we can write to __ro_after_init values during __init */ ro_after_init |= 0xAA; - } diff --git a/drivers/misc/lkdtm/usercopy.c b/drivers/misc/lkdtm/usercopy.c index e172719dd86d0..b833367a45d05 100644 --- a/drivers/misc/lkdtm/usercopy.c +++ b/drivers/misc/lkdtm/usercopy.c @@ -304,19 +304,22 @@ void lkdtm_USERCOPY_KERNEL(void) return; } - pr_info("attempting good copy_to_user from kernel rodata\n"); + pr_info("attempting good copy_to_user from kernel rodata: %px\n", + test_text); if (copy_to_user((void __user *)user_addr, test_text, unconst + sizeof(test_text))) { pr_warn("copy_to_user failed unexpectedly?!\n"); goto free_user; } - pr_info("attempting bad copy_to_user from kernel text\n"); + pr_info("attempting bad copy_to_user from kernel text: %px\n", + vm_mmap); if (copy_to_user((void __user *)user_addr, vm_mmap, unconst + PAGE_SIZE)) { pr_warn("copy_to_user failed, but lacked Oops\n"); goto free_user; } + pr_err("FAIL: survived bad copy_to_user()\n"); free_user: vm_munmap(user_addr, PAGE_SIZE); -- 2.25.1