From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: ARC-Seal: i=1; a=rsa-sha256; t=1526488136; cv=none; d=google.com; s=arc-20160816; b=fmupRJAiZNSpKHzcRfv87mOWUJk75fzVopeJX7+NVOetn1YpxMlU3EUxEAebVpXOux Nw/g55tMelim9h+MFAGKiLi7ULoC4yo3Q910M4NpTIQqo3W1kRAdYpE5sRJBgQXTZ5Ve r0qMCHk8UAsE/ugUiDd0pfvX9WW1Ecv0m3IaJmpOAf9g4ny7AvMMdChFUilGPrB7GgoM XC3cnGcB6k+wgkal7rcoXBPdYlvA0UO/w6tSt7uPpe2NGC5nJHtOjPy9volrwoqu+YNT /mswoarCAf/uOq6qy8DZg0REFvxU0wVEIIC9EJvRXaPzlQyKpzWGxLEdx2lX3bRJSehc wGmw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=references:in-reply-to:message-id:date:subject:to:from :arc-authentication-results; bh=yG8WI64gesDH1VxIEInLOPqtrbP0jMf2nhukF0giWlE=; b=sOKWG2iGJbLQ8CmsseqIPXKtv3/zPHEP2m7RcZ/cDvID+I1SPXIJuiDEjlN+MvRRyg 2rOI5P1tO9M1Yq8UMGzbSyQHnxRuI4pXsjM3gusYtYvkG0W0eTpKHvGV8NYhU2iPMfqu QtJanq/v8FWORXfT0+iYejnu8yNvEx9CV+pqQD68aJlwkLVlpLDAglv1L6aqbiMQ02Y7 OkyaxS/ujkwMEtN+8s86SzSG7ubd0wJuzkdo5PO8peGgeuSQAp4BhzQf2bVerzF3rYVC ou7EPUitsjD1G2Ahm8T8qK0adm7Co5O9rp0Jyck3bz7v/gLhL2Cfq+GBCruv+lO4TKyu v6UA== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of a13xp0p0v88@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=a13xp0p0v88@gmail.com Authentication-Results: mx.google.com; spf=pass (google.com: domain of a13xp0p0v88@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=a13xp0p0v88@gmail.com X-Google-Smtp-Source: AB8JxZryjR/lAeKrUdUABVWtT0CkCNboMmDctEJAOtt/LClKnsiq5uKm9CvFffYNao9GCdhqTWb23w== 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 , Richard Sandiford , Thomas Gleixner , "H . Peter Anvin" , Peter Zijlstra , "Dmitry V . Levin" , Emese Revfy , Jonathan Corbet , Andrey Ryabinin , "Kirill A . Shutemov" , Thomas Garnier , Andrew Morton , Alexei Starovoitov , Josef Bacik , Masami Hiramatsu , Nicholas Piggin , Al Viro , "David S . Miller" , Ding Tianhong , David Woodhouse , Josh Poimboeuf , Steven Rostedt , Dominik Brodowski , Juergen Gross , Linus Torvalds , Greg Kroah-Hartman , Dan Williams , Dave Hansen , Mathias Krause , Vikas Shivappa , Kyle Huey , Dmitry Safonov , Will Deacon , Arnd Bergmann , Florian Weimer , Boris Lukashev , Andrey Konovalov , x86@kernel.org, linux-kernel@vger.kernel.org, alex.popov@linux.com Subject: [PATCH v12 6/6] doc: self-protection: Add information about STACKLEAK feature Date: Wed, 16 May 2018 19:28:17 +0300 Message-Id: <1526488097-20611-7-git-send-email-alex.popov@linux.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1526488097-20611-1-git-send-email-alex.popov@linux.com> References: <1526488097-20611-1-git-send-email-alex.popov@linux.com> X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1600638824413823271?= X-GMAIL-MSGID: =?utf-8?q?1600638824413823271?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 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 -------------------- -- 2.7.4