From patchwork Sun Oct 22 00:22:53 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Popov X-Patchwork-Id: 10021523 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 BB1F7600CC for ; Sun, 22 Oct 2017 00:24:09 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A3BAB286F1 for ; Sun, 22 Oct 2017 00:24:09 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 96C5D288F6; Sun, 22 Oct 2017 00:24:09 +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=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED 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 9048E286F1 for ; Sun, 22 Oct 2017 00:24:08 +0000 (UTC) Received: (qmail 15625 invoked by uid 550); 22 Oct 2017 00:23:28 -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 15497 invoked from network); 22 Oct 2017 00:23:23 -0000 X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:subject:date:message-id:in-reply-to :references; bh=k+Xor7MdRQ/F+Vru095p3JqLE9jEZDmqmwZYJFYGqE0=; b=XMkgIF3qp/us6gJ/GbSfo3VXG6aPCqlAqcrgYGvA1dn4qq0pG5Pr2CYGrpPgT6g7/C TklCRpjZh/MvCJXW3OiszqcmTzPeK2n2Tlv4HGKsM4UTK/B9Ml6E/WYFY5OI6GlDue5N J3j+CMHqJnFEn2Ft+tuhe76JUl4yKZiGYMU79y/XBJKpd+VC9jE442alN94heGRbPr9O M5ezeq4z4Xtce61M7glZWf62m3I9e6lKUmxcMHTe8QfB7VO6LeTHPtz/fPWzJBRlUFTi eWxhOEPFDcAtirHolxU04g2NbjfnSt4g94zWpma8FZgdFTenxWbnbQyNSVN2bL9ylWnB 0LAA== X-Gm-Message-State: AMCzsaW+OoeV7v8goFR1YyE9aphTUszPcd8W2cjnWi3Ysn1c6a65lY7g Xip+BToEQmvtw6ZLCA9aXPCQPHV0 X-Google-Smtp-Source: ABhQp+Q45sjYPozMjFIoeCcWnSFToBPjGn437O8DjiKGWUK0a/grCYwZZZDjsie0cIttrUOfVbYGBQ== X-Received: by 10.46.70.26 with SMTP id t26mr1058111lja.181.1508631792309; Sat, 21 Oct 2017 17:23:12 -0700 (PDT) From: Alexander Popov To: kernel-hardening@lists.openwall.com, keescook@chromium.org, pageexec@freemail.hu, spender@grsecurity.net, Ingo Molnar , Andy Lutomirski , tycho@docker.com, Laura Abbott , Mark Rutland , Ard Biesheuvel , Borislav Petkov , Thomas Gleixner , "H . Peter Anvin" , Peter Zijlstra , x86@kernel.org, alex.popov@linux.com Date: Sun, 22 Oct 2017 03:22:53 +0300 Message-Id: <1508631773-2502-6-git-send-email-alex.popov@linux.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1508631773-2502-1-git-send-email-alex.popov@linux.com> References: <1508631773-2502-1-git-send-email-alex.popov@linux.com> Subject: [kernel-hardening] [PATCH RFC v5 5/5] doc: self-protection: Add information about STACKLEAK feature X-Virus-Scanned: ClamAV using ClamSMTP Add information about STACKLEAK feature to "Stack depth overflow" and "Memory poisoning" sections of self-protection.rst. Signed-off-by: Alexander Popov --- Documentation/security/self-protection.rst | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) diff --git a/Documentation/security/self-protection.rst b/Documentation/security/self-protection.rst index 60c8bd8..9693a90 100644 --- a/Documentation/security/self-protection.rst +++ b/Documentation/security/self-protection.rst @@ -165,10 +165,15 @@ Stack depth overflow A less well understood attack is using a bug that triggers the kernel to consume stack memory with deep function calls or large stack allocations. With this attack it is possible to write beyond the end of -the kernel's preallocated stack space and into sensitive structures. Two -important changes need to be made for better protections: moving the -sensitive thread_info structure elsewhere, and adding a faulting memory -hole at the bottom of the stack to catch these overflows. +the kernel's preallocated stack space and into sensitive structures. +The combination of the following measures gives better protection: + +* moving the sensitive thread_info structure off the stack + (``CONFIG_THREAD_INFO_IN_TASK``); +* adding a faulting memory hole at the bottom of the stack to catch + these overflows (``CONFIG_VMAP_STACK``); +* runtime checking that alloca() calls don't overstep the stack boundary + (``CONFIG_GCC_PLUGIN_STACKLEAK``). Heap memory integrity --------------------- @@ -287,11 +292,11 @@ sure structure holes are cleared. Memory poisoning ---------------- -When releasing memory, it is best to poison the contents (clear stack on -syscall return, wipe heap memory on a free), to avoid reuse attacks that -rely on the old contents of memory. This frustrates many uninitialized -variable attacks, stack content exposures, heap content exposures, and -use-after-free attacks. +When releasing memory, it is best to poison the contents, to avoid reuse +attacks that rely on the old contents of memory. E.g., clear stack on a +syscall return (``CONFIG_GCC_PLUGIN_STACKLEAK``), wipe heap memory on a +free. This frustrates many uninitialized variable attacks, stack content +exposures, heap content exposures, and use-after-free attacks. Destination tracking --------------------