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Message-ID: <CAGXu5jKbqOvb2TtfpXhjPQFxEShaBu=RbBQORtqhcF1bD3As6w@mail.gmail.com>
Date: Thu, 23 Mar 2017 13:15:08 -0700
From: Kees Cook <keescook@...omium.org>
To: Thomas Garnier <thgarnie@...gle.com>
Cc: Martin Schwidefsky <schwidefsky@...ibm.com>, Heiko Carstens <heiko.carstens@...ibm.com>,
David Howells <dhowells@...hat.com>, Arnd Bergmann <arnd@...db.de>, Dave Hansen <dave.hansen@...el.com>,
Al Viro <viro@...iv.linux.org.uk>, Thomas Gleixner <tglx@...utronix.de>,
René Nyffenegger <mail@...enyffenegger.ch>,
Andrew Morton <akpm@...ux-foundation.org>,
"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>, Ingo Molnar <mingo@...nel.org>,
Oleg Nesterov <oleg@...hat.com>, Pavel Tikhomirov <ptikhomirov@...tuozzo.com>,
Stephen Smalley <sds@...ho.nsa.gov>, Ingo Molnar <mingo@...hat.com>, "H . Peter Anvin" <hpa@...or.com>,
Andy Lutomirski <luto@...nel.org>, Paolo Bonzini <pbonzini@...hat.com>, Rik van Riel <riel@...hat.com>,
Josh Poimboeuf <jpoimboe@...hat.com>, Borislav Petkov <bp@...en8.de>, Brian Gerst <brgerst@...il.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
Christian Borntraeger <borntraeger@...ibm.com>, Russell King <linux@...linux.org.uk>,
Will Deacon <will.deacon@....com>, Catalin Marinas <catalin.marinas@....com>,
Mark Rutland <mark.rutland@....com>, James Morse <james.morse@....com>,
"linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
Linux API <linux-api@...r.kernel.org>, "x86@...nel.org" <x86@...nel.org>,
"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH v5 1/4] syscalls: Restore address limit after a syscall
On Thu, Mar 23, 2017 at 10:25 AM, Thomas Garnier <thgarnie@...gle.com> wrote:
> This patch ensures a syscall does not return to user-mode with a kernel
> address limit. If that happened, a process can corrupt kernel-mode
> memory and elevate privileges.
>
> For example, it would mitigation this bug:
>
> - https://bugs.chromium.org/p/project-zero/issues/detail?id=990
>
> The CONFIG_ARCH_NO_SYSCALL_VERIFY_PRE_USERMODE_STATE option is also
> added so each architecture can optimize this change.
>
> Signed-off-by: Thomas Garnier <thgarnie@...gle.com>
Awesome. :) I've tested this on x86 and arm with the LKDTM patch I'll
post in a moment.
[ 46.977823] lkdtm: Performing direct entry CORRUPT_USER_DS
[ 46.978966] lkdtm: setting bad task size limit
[ 46.980302] ------------[ cut here ]------------
[ 46.981219] kernel BUG at ./include/linux/syscalls.h:200!
Tested-by: Kees Cook <keescook@...omium.org>
(Also note, your Signed-off-by lines are missing in patches 2-4)
--
Kees Cook
Pixel Security
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