From patchwork Fri Feb 16 18:10:57 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Popov X-Patchwork-Id: 10225317 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 E0148603EE for ; Fri, 16 Feb 2018 18:12:34 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id CCFED283E7 for ; Fri, 16 Feb 2018 18:12:34 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id BE79F2845E; Fri, 16 Feb 2018 18:12:34 +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 E0780283E7 for ; Fri, 16 Feb 2018 18:12:33 +0000 (UTC) Received: (qmail 17976 invoked by uid 550); 16 Feb 2018 18:11:37 -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 17897 invoked from network); 16 Feb 2018 18:11:34 -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=yG8WI64gesDH1VxIEInLOPqtrbP0jMf2nhukF0giWlE=; b=tr87TZsxxY4Y9R/BNp2fjMNAvTC9M/JE4Y1VVOHq97ju/OcJNkhmE+UxXpVdCV3UAf CaWayPl3MfUlfw6S4Y9hcppXP8siqXtYEaS4zHULRNOdopEqFYvZP1FfHGT8EGG9Dk/y YmfICUwi1gpRF/aKlHWPQGf+dCcoI9adBAybGamk8VYediEpYvSLQ8kDE2d0J3ScvZ8h wh2ZcFNVQri4/VRjZ1YHFSgVcU+oCYM1wEzklYgIf/yFIF8OpuF3a8YLNMWAhM8cnWv/ hRf7FfjvEkFMu1/E5UNjQoDLkT50m6yt+Nulu8R8Jn/GMl55T1U0z3Qq5XHkjJ5bRd4K orJg== X-Gm-Message-State: APf1xPDqYdM73AHKZ05lk0I0dbMa6pZYIgsIatBih9dDLdGCK0XvQRtF zQeGHDdKakVSOh3xMViJ+Y71sr+R0z4= X-Google-Smtp-Source: AH8x225pkWCAXsqTxCB6jXdtJk/1Ks8e2KBc0OWMGKcu5vN1nxaLDfy/lWwZ8DwPb8XUtGXXX9Tu1Q== X-Received: by 10.25.222.207 with SMTP id i76mr4253960lfl.133.1518804683481; Fri, 16 Feb 2018 10:11:23 -0800 (PST) From: Alexander Popov To: kernel-hardening@lists.openwall.com, Kees Cook , PaX Team , Brad Spengler , Ingo Molnar , Andy Lutomirski , Tycho Andersen , Laura Abbott , Mark Rutland , Ard Biesheuvel , Borislav Petkov , Thomas Gleixner , "H . Peter Anvin" , Peter Zijlstra , "Dmitry V . Levin" , x86@kernel.org, alex.popov@linux.com Subject: [PATCH RFC v8 6/6] doc: self-protection: Add information about STACKLEAK feature Date: Fri, 16 Feb 2018 21:10:57 +0300 Message-Id: <1518804657-24905-7-git-send-email-alex.popov@linux.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1518804657-24905-1-git-send-email-alex.popov@linux.com> References: <1518804657-24905-1-git-send-email-alex.popov@linux.com> 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 0f53826..b685f18 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 --------------------- @@ -302,11 +307,11 @@ 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 --------------------