From patchwork Sun Mar 26 21:08:25 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eddie Kovsky X-Patchwork-Id: 9645227 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 453B360327 for ; Sun, 26 Mar 2017 21:09:19 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 36BE827F80 for ; Sun, 26 Mar 2017 21:09:19 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 2B43927F9F; Sun, 26 Mar 2017 21:09:19 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.1 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_MED,T_DKIM_INVALID autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 5EA5627F80 for ; Sun, 26 Mar 2017 21:09:18 +0000 (UTC) Received: (qmail 7908 invoked by uid 550); 26 Mar 2017 21:09:16 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 7890 invoked from network); 26 Mar 2017 21:09:16 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=edkovsky.org; s=mail; t=1490562544; bh=+EFdoNIaA4gm94LbO0rnlY1H2vJCjUSgoYkDtEPQ+k8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NkBul76JnKpcQlSU9jZ68xFgCCjKZR88vGVhClVQB/7XPEnTjanxOBalRwu6VZgp0 catEi0WpVsyvZAwzjRqdUFZiWiyPze6FNrjpgLFJmXgN4XadkoayijMcze3pg93aJy 8Z7PDIV8Q3FJx30MLLQSQ8V6lhQ7m+Aq5hWCVGhQ= From: Eddie Kovsky To: jeyu@redhat.com, rusty@rustcorp.com.au, keescook@chromium.org Cc: linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com Date: Sun, 26 Mar 2017 15:08:25 -0600 Message-Id: <20170326210825.23255-3-ewk@edkovsky.org> X-Mailer: git-send-email 2.12.1 In-Reply-To: <20170326210825.23255-1-ewk@edkovsky.org> References: <20170326210825.23255-1-ewk@edkovsky.org> X-Virus-Scanned: clamav-milter 0.99.2 at olympus X-Virus-Status: Clean Subject: [kernel-hardening] [PATCH v4 2/2] extable: verify address is read-only X-Virus-Scanned: ClamAV using ClamSMTP Provide a mechanism to check if the address of a variable is const or ro_after_init. It mimics the existing functions that test if an address is inside the kernel's text section. The idea is to prevent structures that are not read-only from being passed to functions. Other functions inside the kernel could then use this capability to verify that their arguments are read-only. This implements the first half of a suggestion made by Kees Cook for the Kernel Self Protection Project: - provide mechanism to check for ro_after_init memory areas, and reject structures not marked ro_after_init in vmbus_register() Suggested-by: Kees Cook Signed-off-by: Eddie Kovsky --- Changes in v4: - Rename function core_kernel_ro_data() to core_kernel_rodata(). Changes in v3: - Fix missing declaration of is_module_rodata_address() --- include/linux/kernel.h | 2 ++ kernel/extable.c | 29 +++++++++++++++++++++++++++++ 2 files changed, 31 insertions(+) diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 4c26dc3a8295..5748784ca209 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -444,6 +444,8 @@ extern int core_kernel_data(unsigned long addr); extern int __kernel_text_address(unsigned long addr); extern int kernel_text_address(unsigned long addr); extern int func_ptr_is_kernel_text(void *ptr); +extern int core_kernel_rodata(unsigned long addr); +extern int kernel_ro_address(unsigned long addr); unsigned long int_sqrt(unsigned long); diff --git a/kernel/extable.c b/kernel/extable.c index 2676d7f8baf6..22562cfc6ac3 100644 --- a/kernel/extable.c +++ b/kernel/extable.c @@ -154,3 +154,32 @@ int func_ptr_is_kernel_text(void *ptr) return 1; return is_module_text_address(addr); } + +/** + * core_kernel_rodata - Verify address points to read-only section + * @addr: address to test + * + */ +int core_kernel_rodata(unsigned long addr) +{ + if (addr >= (unsigned long)__start_rodata && + addr < (unsigned long)__end_rodata) + return 1; + + if (addr >= (unsigned long)__start_data_ro_after_init && + addr < (unsigned long)__end_data_ro_after_init) + return 1; + + return 0; +} + +/* Verify that address is const or ro_after_init. */ +int kernel_ro_address(unsigned long addr) +{ + if (core_kernel_rodata(addr)) + return 1; + if (is_module_rodata_address(addr)) + return 1; + + return 0; +}