From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751439AbcGNSK0 (ORCPT ); Thu, 14 Jul 2016 14:10:26 -0400 Received: from mail-wm0-f54.google.com ([74.125.82.54]:38579 "EHLO mail-wm0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751161AbcGNSKV (ORCPT ); Thu, 14 Jul 2016 14:10:21 -0400 MIME-Version: 1.0 In-Reply-To: <20160714054842.6zal5rqawpgew26r@treble> References: <1468446964-22213-1-git-send-email-keescook@chromium.org> <1468446964-22213-2-git-send-email-keescook@chromium.org> <20160714054842.6zal5rqawpgew26r@treble> From: Kees Cook Date: Thu, 14 Jul 2016 11:10:18 -0700 X-Google-Sender-Auth: JdtCRW9L89-aYCN1FlGF4DxI03M Message-ID: Subject: Re: [PATCH v2 01/11] mm: Implement stack frame object validation To: Josh Poimboeuf Cc: Andy Lutomirski , "linux-kernel@vger.kernel.org" , Rik van Riel , Casey Schaufler , PaX Team , Brad Spengler , Russell King , Catalin Marinas , Will Deacon , Ard Biesheuvel , Benjamin Herrenschmidt , Michael Ellerman , Tony Luck , Fenghua Yu , "David S. Miller" , X86 ML , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Andy Lutomirski , Borislav Petkov , Mathias Krause , Jan Kara , Vitaly Wool , Andrea Arcangeli , Dmitry Vyukov , Laura Abbott , "linux-arm-kernel@lists.infradead.org" , "linux-ia64@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , sparclinux , linux-arch , "linux-mm@kvack.org" , "kernel-hardening@lists.openwall.com" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 13, 2016 at 10:48 PM, Josh Poimboeuf wrote: > On Wed, Jul 13, 2016 at 03:04:26PM -0700, Kees Cook wrote: >> On Wed, Jul 13, 2016 at 3:01 PM, Andy Lutomirski wrote: >> > On Wed, Jul 13, 2016 at 2:55 PM, Kees Cook wrote: >> >> This creates per-architecture function arch_within_stack_frames() that >> >> should validate if a given object is contained by a kernel stack frame. >> >> Initial implementation is on x86. >> >> >> >> This is based on code from PaX. >> >> >> > >> > This, along with Josh's livepatch work, are two examples of unwinders >> > that matter for correctness instead of just debugging. ISTM this >> > should just use Josh's code directly once it's been written. >> >> Do you have URL for Josh's code? I'd love to see what happening there. > > The code is actually going to be 100% different next time around, but > FWIW, here's the last attempt: > > https://lkml.kernel.org/r/4d34d452bf8f85c7d6d5f93db1d3eeb4cba335c7.1461875890.git.jpoimboe@redhat.com > > In the meantime I've realized the need to rewrite the x86 core stack > walking code to something much more manageable so we don't need all > these unwinders everywhere. I'll probably post the patches in the next > week or so. I'll add you to the CC list. Awesome! > With the new interface I think you'll be able to do something like: > > struct unwind_state; > > unwind_start(&state, current, NULL, NULL); > unwind_next_frame(&state); > oldframe = unwind_get_stack_pointer(&state); > > unwind_next_frame(&state); > frame = unwind_get_stack_pointer(&state); > > do { > if (obj + len <= frame) > return blah; > oldframe = frame; > frame = unwind_get_stack_pointer(&state); > > } while (unwind_next_frame(&state); > > And then at the end there'll be some (still TBD) way to query whether it > reached the last syscall pt_regs frame, or if it instead encountered a > bogus frame pointer along the way and had to bail early. Sounds good to me. Will there be any frame size information available? Right now, the unwinder from PaX just drops 2 pointers (saved frame, saved ip) from the delta of frame address to find the size of the actual stack area used by the function. If I could shave things like padding and possible stack canaries off the size too, that would be great. Since I'm aiming the hardened usercopy series for 4.8, I figure I'll just leave this unwinder in for now, and once yours lands, I can rip it out again. -Kees -- Kees Cook Chrome OS & Brillo Security From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kees Cook Subject: Re: [PATCH v2 01/11] mm: Implement stack frame object validation Date: Thu, 14 Jul 2016 11:10:18 -0700 Message-ID: References: <1468446964-22213-1-git-send-email-keescook@chromium.org> <1468446964-22213-2-git-send-email-keescook@chromium.org> <20160714054842.6zal5rqawpgew26r@treble> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: In-Reply-To: <20160714054842.6zal5rqawpgew26r@treble> Sender: owner-linux-mm@kvack.org To: Josh Poimboeuf Cc: Andy Lutomirski , "linux-kernel@vger.kernel.org" , Rik van Riel , Casey Schaufler , PaX Team , Brad Spengler , Russell King , Catalin Marinas , Will Deacon , Ard Biesheuvel , Benjamin Herrenschmidt , Michael Ellerman , Tony Luck , Fenghua Yu , "David S. Miller" , X86 ML , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Andy Lutomirski Borislav Petkov List-Id: linux-arch.vger.kernel.org On Wed, Jul 13, 2016 at 10:48 PM, Josh Poimboeuf wrote: > On Wed, Jul 13, 2016 at 03:04:26PM -0700, Kees Cook wrote: >> On Wed, Jul 13, 2016 at 3:01 PM, Andy Lutomirski wrote: >> > On Wed, Jul 13, 2016 at 2:55 PM, Kees Cook wrote: >> >> This creates per-architecture function arch_within_stack_frames() that >> >> should validate if a given object is contained by a kernel stack frame. >> >> Initial implementation is on x86. >> >> >> >> This is based on code from PaX. >> >> >> > >> > This, along with Josh's livepatch work, are two examples of unwinders >> > that matter for correctness instead of just debugging. ISTM this >> > should just use Josh's code directly once it's been written. >> >> Do you have URL for Josh's code? I'd love to see what happening there. > > The code is actually going to be 100% different next time around, but > FWIW, here's the last attempt: > > https://lkml.kernel.org/r/4d34d452bf8f85c7d6d5f93db1d3eeb4cba335c7.1461875890.git.jpoimboe@redhat.com > > In the meantime I've realized the need to rewrite the x86 core stack > walking code to something much more manageable so we don't need all > these unwinders everywhere. I'll probably post the patches in the next > week or so. I'll add you to the CC list. Awesome! > With the new interface I think you'll be able to do something like: > > struct unwind_state; > > unwind_start(&state, current, NULL, NULL); > unwind_next_frame(&state); > oldframe = unwind_get_stack_pointer(&state); > > unwind_next_frame(&state); > frame = unwind_get_stack_pointer(&state); > > do { > if (obj + len <= frame) > return blah; > oldframe = frame; > frame = unwind_get_stack_pointer(&state); > > } while (unwind_next_frame(&state); > > And then at the end there'll be some (still TBD) way to query whether it > reached the last syscall pt_regs frame, or if it instead encountered a > bogus frame pointer along the way and had to bail early. Sounds good to me. Will there be any frame size information available? Right now, the unwinder from PaX just drops 2 pointers (saved frame, saved ip) from the delta of frame address to find the size of the actual stack area used by the function. If I could shave things like padding and possible stack canaries off the size too, that would be great. Since I'm aiming the hardened usercopy series for 4.8, I figure I'll just leave this unwinder in for now, and once yours lands, I can rip it out again. -Kees -- Kees Cook Chrome OS & Brillo Security -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f53.google.com ([74.125.82.53]:36195 "EHLO mail-wm0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751098AbcGNSKV (ORCPT ); Thu, 14 Jul 2016 14:10:21 -0400 Received: by mail-wm0-f53.google.com with SMTP id f126so75434006wma.1 for ; Thu, 14 Jul 2016 11:10:20 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20160714054842.6zal5rqawpgew26r@treble> References: <1468446964-22213-1-git-send-email-keescook@chromium.org> <1468446964-22213-2-git-send-email-keescook@chromium.org> <20160714054842.6zal5rqawpgew26r@treble> From: Kees Cook Date: Thu, 14 Jul 2016 11:10:18 -0700 Message-ID: Subject: Re: [PATCH v2 01/11] mm: Implement stack frame object validation Content-Type: text/plain; charset=UTF-8 Sender: linux-arch-owner@vger.kernel.org List-ID: To: Josh Poimboeuf Cc: Andy Lutomirski , "linux-kernel@vger.kernel.org" , Rik van Riel , Casey Schaufler , PaX Team , Brad Spengler , Russell King , Catalin Marinas , Will Deacon , Ard Biesheuvel , Benjamin Herrenschmidt , Michael Ellerman , Tony Luck , Fenghua Yu , "David S. Miller" , X86 ML , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Andy Lutomirski , Borislav Petkov , Mathias Krause , Jan Kara , Vitaly Wool , Andrea Arcangeli , Dmitry Vyukov , Laura Abbott , "linux-arm-kernel@lists.infradead.org" , "linux-ia64@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , sparclinux , linux-arch , "linux-mm@kvack.org" , "kernel-hardening@lists.openwall.com" Message-ID: <20160714181018.tSYj6WlUwnMzUr7ADthZ5QPVEy9mYjoraJMMtvG9fg4@z> On Wed, Jul 13, 2016 at 10:48 PM, Josh Poimboeuf wrote: > On Wed, Jul 13, 2016 at 03:04:26PM -0700, Kees Cook wrote: >> On Wed, Jul 13, 2016 at 3:01 PM, Andy Lutomirski wrote: >> > On Wed, Jul 13, 2016 at 2:55 PM, Kees Cook wrote: >> >> This creates per-architecture function arch_within_stack_frames() that >> >> should validate if a given object is contained by a kernel stack frame. >> >> Initial implementation is on x86. >> >> >> >> This is based on code from PaX. >> >> >> > >> > This, along with Josh's livepatch work, are two examples of unwinders >> > that matter for correctness instead of just debugging. ISTM this >> > should just use Josh's code directly once it's been written. >> >> Do you have URL for Josh's code? I'd love to see what happening there. > > The code is actually going to be 100% different next time around, but > FWIW, here's the last attempt: > > https://lkml.kernel.org/r/4d34d452bf8f85c7d6d5f93db1d3eeb4cba335c7.1461875890.git.jpoimboe@redhat.com > > In the meantime I've realized the need to rewrite the x86 core stack > walking code to something much more manageable so we don't need all > these unwinders everywhere. I'll probably post the patches in the next > week or so. I'll add you to the CC list. Awesome! > With the new interface I think you'll be able to do something like: > > struct unwind_state; > > unwind_start(&state, current, NULL, NULL); > unwind_next_frame(&state); > oldframe = unwind_get_stack_pointer(&state); > > unwind_next_frame(&state); > frame = unwind_get_stack_pointer(&state); > > do { > if (obj + len <= frame) > return blah; > oldframe = frame; > frame = unwind_get_stack_pointer(&state); > > } while (unwind_next_frame(&state); > > And then at the end there'll be some (still TBD) way to query whether it > reached the last syscall pt_regs frame, or if it instead encountered a > bogus frame pointer along the way and had to bail early. Sounds good to me. Will there be any frame size information available? Right now, the unwinder from PaX just drops 2 pointers (saved frame, saved ip) from the delta of frame address to find the size of the actual stack area used by the function. If I could shave things like padding and possible stack canaries off the size too, that would be great. Since I'm aiming the hardened usercopy series for 4.8, I figure I'll just leave this unwinder in for now, and once yours lands, I can rip it out again. -Kees -- Kees Cook Chrome OS & Brillo Security From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kees Cook Date: Thu, 14 Jul 2016 18:10:18 +0000 Subject: Re: [PATCH v2 01/11] mm: Implement stack frame object validation Message-Id: List-Id: References: <1468446964-22213-1-git-send-email-keescook@chromium.org> <1468446964-22213-2-git-send-email-keescook@chromium.org> <20160714054842.6zal5rqawpgew26r@treble> In-Reply-To: <20160714054842.6zal5rqawpgew26r@treble> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Josh Poimboeuf Cc: Andy Lutomirski , "linux-kernel@vger.kernel.org" , Rik van Riel , Casey Schaufler , PaX Team , Brad Spengler , Russell King , Catalin Marinas , Will Deacon , Ard Biesheuvel , Benjamin Herrenschmidt , Michael Ellerman , Tony Luck , Fenghua Yu , "David S. Miller" , X86 ML , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Andy Lutomirski , Borislav Petkov , Mathias Krause , Jan Kara , Vitaly Wool , Andrea Arcangeli , Dmitry Vyukov , Laura Abbott , "linux-arm-kernel@lists.infradead.org" , "linux-ia64@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , sparclinux , linux-arch , "linux-mm@kvack.org" , "kernel-hardening@lists.openwall.com" On Wed, Jul 13, 2016 at 10:48 PM, Josh Poimboeuf wrote: > On Wed, Jul 13, 2016 at 03:04:26PM -0700, Kees Cook wrote: >> On Wed, Jul 13, 2016 at 3:01 PM, Andy Lutomirski wrote: >> > On Wed, Jul 13, 2016 at 2:55 PM, Kees Cook wrote: >> >> This creates per-architecture function arch_within_stack_frames() that >> >> should validate if a given object is contained by a kernel stack frame. >> >> Initial implementation is on x86. >> >> >> >> This is based on code from PaX. >> >> >> > >> > This, along with Josh's livepatch work, are two examples of unwinders >> > that matter for correctness instead of just debugging. ISTM this >> > should just use Josh's code directly once it's been written. >> >> Do you have URL for Josh's code? I'd love to see what happening there. > > The code is actually going to be 100% different next time around, but > FWIW, here's the last attempt: > > https://lkml.kernel.org/r/4d34d452bf8f85c7d6d5f93db1d3eeb4cba335c7.1461875890.git.jpoimboe@redhat.com > > In the meantime I've realized the need to rewrite the x86 core stack > walking code to something much more manageable so we don't need all > these unwinders everywhere. I'll probably post the patches in the next > week or so. I'll add you to the CC list. Awesome! > With the new interface I think you'll be able to do something like: > > struct unwind_state; > > unwind_start(&state, current, NULL, NULL); > unwind_next_frame(&state); > oldframe = unwind_get_stack_pointer(&state); > > unwind_next_frame(&state); > frame = unwind_get_stack_pointer(&state); > > do { > if (obj + len <= frame) > return blah; > oldframe = frame; > frame = unwind_get_stack_pointer(&state); > > } while (unwind_next_frame(&state); > > And then at the end there'll be some (still TBD) way to query whether it > reached the last syscall pt_regs frame, or if it instead encountered a > bogus frame pointer along the way and had to bail early. Sounds good to me. Will there be any frame size information available? Right now, the unwinder from PaX just drops 2 pointers (saved frame, saved ip) from the delta of frame address to find the size of the actual stack area used by the function. If I could shave things like padding and possible stack canaries off the size too, that would be great. Since I'm aiming the hardened usercopy series for 4.8, I figure I'll just leave this unwinder in for now, and once yours lands, I can rip it out again. -Kees -- Kees Cook Chrome OS & Brillo Security From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f71.google.com (mail-wm0-f71.google.com [74.125.82.71]) by kanga.kvack.org (Postfix) with ESMTP id B28C06B0005 for ; Thu, 14 Jul 2016 14:10:21 -0400 (EDT) Received: by mail-wm0-f71.google.com with SMTP id f126so61374336wma.3 for ; Thu, 14 Jul 2016 11:10:21 -0700 (PDT) Received: from mail-wm0-x22d.google.com (mail-wm0-x22d.google.com. [2a00:1450:400c:c09::22d]) by mx.google.com with ESMTPS id v129si4729641wme.91.2016.07.14.11.10.19 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 14 Jul 2016 11:10:19 -0700 (PDT) Received: by mail-wm0-x22d.google.com with SMTP id o80so123410451wme.1 for ; Thu, 14 Jul 2016 11:10:19 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20160714054842.6zal5rqawpgew26r@treble> References: <1468446964-22213-1-git-send-email-keescook@chromium.org> <1468446964-22213-2-git-send-email-keescook@chromium.org> <20160714054842.6zal5rqawpgew26r@treble> From: Kees Cook Date: Thu, 14 Jul 2016 11:10:18 -0700 Message-ID: Subject: Re: [PATCH v2 01/11] mm: Implement stack frame object validation Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Josh Poimboeuf Cc: Andy Lutomirski , "linux-kernel@vger.kernel.org" , Rik van Riel , Casey Schaufler , PaX Team , Brad Spengler , Russell King , Catalin Marinas , Will Deacon , Ard Biesheuvel , Benjamin Herrenschmidt , Michael Ellerman , Tony Luck , Fenghua Yu , "David S. Miller" , X86 ML , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Andy Lutomirski , Borislav Petkov , Mathias Krause , Jan Kara , Vitaly Wool , Andrea Arcangeli , Dmitry Vyukov , Laura Abbott , "linux-arm-kernel@lists.infradead.org" , "linux-ia64@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , sparclinux , linux-arch , "linux-mm@kvack.org" , "kernel-hardening@lists.openwall.com" On Wed, Jul 13, 2016 at 10:48 PM, Josh Poimboeuf wrote: > On Wed, Jul 13, 2016 at 03:04:26PM -0700, Kees Cook wrote: >> On Wed, Jul 13, 2016 at 3:01 PM, Andy Lutomirski wrote: >> > On Wed, Jul 13, 2016 at 2:55 PM, Kees Cook wrote: >> >> This creates per-architecture function arch_within_stack_frames() that >> >> should validate if a given object is contained by a kernel stack frame. >> >> Initial implementation is on x86. >> >> >> >> This is based on code from PaX. >> >> >> > >> > This, along with Josh's livepatch work, are two examples of unwinders >> > that matter for correctness instead of just debugging. ISTM this >> > should just use Josh's code directly once it's been written. >> >> Do you have URL for Josh's code? I'd love to see what happening there. > > The code is actually going to be 100% different next time around, but > FWIW, here's the last attempt: > > https://lkml.kernel.org/r/4d34d452bf8f85c7d6d5f93db1d3eeb4cba335c7.1461875890.git.jpoimboe@redhat.com > > In the meantime I've realized the need to rewrite the x86 core stack > walking code to something much more manageable so we don't need all > these unwinders everywhere. I'll probably post the patches in the next > week or so. I'll add you to the CC list. Awesome! > With the new interface I think you'll be able to do something like: > > struct unwind_state; > > unwind_start(&state, current, NULL, NULL); > unwind_next_frame(&state); > oldframe = unwind_get_stack_pointer(&state); > > unwind_next_frame(&state); > frame = unwind_get_stack_pointer(&state); > > do { > if (obj + len <= frame) > return blah; > oldframe = frame; > frame = unwind_get_stack_pointer(&state); > > } while (unwind_next_frame(&state); > > And then at the end there'll be some (still TBD) way to query whether it > reached the last syscall pt_regs frame, or if it instead encountered a > bogus frame pointer along the way and had to bail early. Sounds good to me. Will there be any frame size information available? Right now, the unwinder from PaX just drops 2 pointers (saved frame, saved ip) from the delta of frame address to find the size of the actual stack area used by the function. If I could shave things like padding and possible stack canaries off the size too, that would be great. Since I'm aiming the hardened usercopy series for 4.8, I figure I'll just leave this unwinder in for now, and once yours lands, I can rip it out again. -Kees -- Kees Cook Chrome OS & Brillo Security -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 From: keescook@chromium.org (Kees Cook) Date: Thu, 14 Jul 2016 11:10:18 -0700 Subject: [PATCH v2 01/11] mm: Implement stack frame object validation In-Reply-To: <20160714054842.6zal5rqawpgew26r@treble> References: <1468446964-22213-1-git-send-email-keescook@chromium.org> <1468446964-22213-2-git-send-email-keescook@chromium.org> <20160714054842.6zal5rqawpgew26r@treble> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Jul 13, 2016 at 10:48 PM, Josh Poimboeuf wrote: > On Wed, Jul 13, 2016 at 03:04:26PM -0700, Kees Cook wrote: >> On Wed, Jul 13, 2016 at 3:01 PM, Andy Lutomirski wrote: >> > On Wed, Jul 13, 2016 at 2:55 PM, Kees Cook wrote: >> >> This creates per-architecture function arch_within_stack_frames() that >> >> should validate if a given object is contained by a kernel stack frame. >> >> Initial implementation is on x86. >> >> >> >> This is based on code from PaX. >> >> >> > >> > This, along with Josh's livepatch work, are two examples of unwinders >> > that matter for correctness instead of just debugging. ISTM this >> > should just use Josh's code directly once it's been written. >> >> Do you have URL for Josh's code? I'd love to see what happening there. > > The code is actually going to be 100% different next time around, but > FWIW, here's the last attempt: > > https://lkml.kernel.org/r/4d34d452bf8f85c7d6d5f93db1d3eeb4cba335c7.1461875890.git.jpoimboe at redhat.com > > In the meantime I've realized the need to rewrite the x86 core stack > walking code to something much more manageable so we don't need all > these unwinders everywhere. I'll probably post the patches in the next > week or so. I'll add you to the CC list. Awesome! > With the new interface I think you'll be able to do something like: > > struct unwind_state; > > unwind_start(&state, current, NULL, NULL); > unwind_next_frame(&state); > oldframe = unwind_get_stack_pointer(&state); > > unwind_next_frame(&state); > frame = unwind_get_stack_pointer(&state); > > do { > if (obj + len <= frame) > return blah; > oldframe = frame; > frame = unwind_get_stack_pointer(&state); > > } while (unwind_next_frame(&state); > > And then at the end there'll be some (still TBD) way to query whether it > reached the last syscall pt_regs frame, or if it instead encountered a > bogus frame pointer along the way and had to bail early. Sounds good to me. Will there be any frame size information available? Right now, the unwinder from PaX just drops 2 pointers (saved frame, saved ip) from the delta of frame address to find the size of the actual stack area used by the function. If I could shave things like padding and possible stack canaries off the size too, that would be great. Since I'm aiming the hardened usercopy series for 4.8, I figure I'll just leave this unwinder in for now, and once yours lands, I can rip it out again. -Kees -- Kees Cook Chrome OS & Brillo Security From mboxrd@z Thu Jan 1 00:00:00 1970 Reply-To: kernel-hardening@lists.openwall.com MIME-Version: 1.0 Sender: keescook@google.com In-Reply-To: <20160714054842.6zal5rqawpgew26r@treble> References: <1468446964-22213-1-git-send-email-keescook@chromium.org> <1468446964-22213-2-git-send-email-keescook@chromium.org> <20160714054842.6zal5rqawpgew26r@treble> From: Kees Cook Date: Thu, 14 Jul 2016 11:10:18 -0700 Message-ID: Content-Type: text/plain; charset=UTF-8 Subject: [kernel-hardening] Re: [PATCH v2 01/11] mm: Implement stack frame object validation To: Josh Poimboeuf Cc: Andy Lutomirski , "linux-kernel@vger.kernel.org" , Rik van Riel , Casey Schaufler , PaX Team , Brad Spengler , Russell King , Catalin Marinas , Will Deacon , Ard Biesheuvel , Benjamin Herrenschmidt , Michael Ellerman , Tony Luck , Fenghua Yu , "David S. Miller" , X86 ML , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Andy Lutomirski , Borislav Petkov , Mathias Krause , Jan Kara , Vitaly Wool , Andrea Arcangeli , Dmitry Vyukov , Laura Abbott , "linux-arm-kernel@lists.infradead.org" , "linux-ia64@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , sparclinux , linux-arch , "linux-mm@kvack.org" , "kernel-hardening@lists.openwall.com" List-ID: On Wed, Jul 13, 2016 at 10:48 PM, Josh Poimboeuf wrote: > On Wed, Jul 13, 2016 at 03:04:26PM -0700, Kees Cook wrote: >> On Wed, Jul 13, 2016 at 3:01 PM, Andy Lutomirski wrote: >> > On Wed, Jul 13, 2016 at 2:55 PM, Kees Cook wrote: >> >> This creates per-architecture function arch_within_stack_frames() that >> >> should validate if a given object is contained by a kernel stack frame. >> >> Initial implementation is on x86. >> >> >> >> This is based on code from PaX. >> >> >> > >> > This, along with Josh's livepatch work, are two examples of unwinders >> > that matter for correctness instead of just debugging. ISTM this >> > should just use Josh's code directly once it's been written. >> >> Do you have URL for Josh's code? I'd love to see what happening there. > > The code is actually going to be 100% different next time around, but > FWIW, here's the last attempt: > > https://lkml.kernel.org/r/4d34d452bf8f85c7d6d5f93db1d3eeb4cba335c7.1461875890.git.jpoimboe@redhat.com > > In the meantime I've realized the need to rewrite the x86 core stack > walking code to something much more manageable so we don't need all > these unwinders everywhere. I'll probably post the patches in the next > week or so. I'll add you to the CC list. Awesome! > With the new interface I think you'll be able to do something like: > > struct unwind_state; > > unwind_start(&state, current, NULL, NULL); > unwind_next_frame(&state); > oldframe = unwind_get_stack_pointer(&state); > > unwind_next_frame(&state); > frame = unwind_get_stack_pointer(&state); > > do { > if (obj + len <= frame) > return blah; > oldframe = frame; > frame = unwind_get_stack_pointer(&state); > > } while (unwind_next_frame(&state); > > And then at the end there'll be some (still TBD) way to query whether it > reached the last syscall pt_regs frame, or if it instead encountered a > bogus frame pointer along the way and had to bail early. Sounds good to me. Will there be any frame size information available? Right now, the unwinder from PaX just drops 2 pointers (saved frame, saved ip) from the delta of frame address to find the size of the actual stack area used by the function. If I could shave things like padding and possible stack canaries off the size too, that would be great. Since I'm aiming the hardened usercopy series for 4.8, I figure I'll just leave this unwinder in for now, and once yours lands, I can rip it out again. -Kees -- Kees Cook Chrome OS & Brillo Security