From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: ARC-Seal: i=1; a=rsa-sha256; t=1520107263; cv=none; d=google.com; s=arc-20160816; b=fUz9hiHtZ72ESnYza/FnoujfMnK96Suid0FG70rkHMeGInYmt2D4Akhmy3f9RZPpVO 7/UEBcAnlzKyfnATUykYOh2k8ybPYOJiOR62uAHjoZL7hLI9z8/4hRsJOie/CpLgNoUh VxeZtpmiJ/FOwp8gyuot63zT+0qsu5RdevuPXU4KkdTMWN/BLshnOTui62ikIcJwuujU QTHG6+GZU1Xgi3I5+CXg/QAEKwYRS9AYFTvZqtzphBfZNanGj1l1HdbrZQkbsjMYeyzU LdXbHNhLvxkM9NV5CPU071Dwb2yx/S2ErUwSywbHX4eaZDlRJy33sXS3qVUoT0rXj5Dj Jfkw== 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=KTqN4C9j8rzoAoknzneZ3CMCXLUPTvIoFIOCAfFL9C6y9DoKAUzLSbzxFiHwb0q2gx VreRcl00PtyrXTbJhLBxuK7QXwg/5VrRR8fhGB1xMVvHNGFZSeJyl+P9gvkdoplZOyxr hdSDhvIC/Xaq78k/YzJMFANLr0nuzcmcTLxoNKekwrU7VVktlPB+uqc+GC8TLVOJyoLg ZUxOFN4iX5GhqTY6is1yih65fvWYgCeSou4ouxwS0N+s0lyaFpKYPeOhIweu/mQS1vg+ p4CLouWjn5kRUaLW82mWgoz3wIrXx+FPw57Cume/s0j2DHW58BSI9RcS9kaoAuYHxiEO eYrw== 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: AG47ELvjWZJJovaOw93cvz3w78ReR3PL0KplllMwVNfY/5jd/8dNv1g6aFuOfeOmtyUU0oR/TxsXBQ== 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 , Greg Kroah-Hartman , Dan Williams , Dave Hansen , Mathias Krause , Vikas Shivappa , Kyle Huey , Dmitry Safonov , Will Deacon , Arnd Bergmann , x86@kernel.org, linux-kernel@vger.kernel.org, alex.popov@linux.com Subject: [PATCH RFC v9 7/7] doc: self-protection: Add information about STACKLEAK feature Date: Sat, 3 Mar 2018 23:00:32 +0300 Message-Id: <1520107232-14111-8-git-send-email-alex.popov@linux.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1520107232-14111-1-git-send-email-alex.popov@linux.com> References: <1520107232-14111-1-git-send-email-alex.popov@linux.com> X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1593947993864604438?= X-GMAIL-MSGID: =?utf-8?q?1593947993864604438?= 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